2086 lines
103 KiB
HTML
2086 lines
103 KiB
HTML
<html>
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<head>
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<title>cgic: an ANSI C library for CGI Programming</title>
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</head>
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<body>
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<h1>cgic 2.07: an ANSI C library for CGI Programming</h1>
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<blockquote>
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<strong>IMPORTANT NOTICES:</strong>
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<p>
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If you have CGIC 1.05 or earlier, you should upgrade to CGIC 1.07,
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or to CGIC 2.02 or better, in order to obtain important security fixes.
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<p>
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If you have CGIC 2.0 or CGIC 2.01 and you use the cgiCookie routines,
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you should upgrade to CGIC 2.02 or better, in order to obtain
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important security fixes.
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</blockquote>
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<h3>Table of Contents</h3>
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<ul>
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<li><a href="#credits">Credits and license terms</a>
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<li><a href="#whatsnew208">What's new in version XYZ of CGIC?</a>
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<li><a href="#whatis">What is cgic?</a>
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<li><a href="#obtain">Obtaining cgic</a>
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<li><a href="#build">Building and testing cgic: a sample application</a>
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<li><a href="#nocompile">What to do if it won't compile</a>
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<li><a href="#howto">How to write a cgic application</a>
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<li><a href="#images">How can I generate images from my cgic application?</a>
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<li><a href="#debug">CGI debugging features: using capture</a>
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<li><a href="#functions">cgic function reference</a>
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<li><a href="#variables">cgic variable reference</a>
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<li><a href="#resultcodes">cgic result code reference</a>
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<li><a href="#index">cgic quick index</a>
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</ul>
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<h3><a name="credits">Credits and License Terms</a></h3>
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<p>
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cgic is now distributed under the MIT license:
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</p>
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<p>
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Copyright (c) 1996-2019 Thomas Boutell
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</p>
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<p>
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Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
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</p>
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<p>
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The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
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</p>
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<p>
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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</p>
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<p>
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Thanks are due to Robert Gustavsson, Ken Holervich, Bob Nestor,
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Jon Ribbens, Thomas Strangert, Wu Yongwei, and other CGIC users
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who have corresponded over the years. Although the implementation
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of multipart/form-data file upload support in CGIC 2.x is my own,
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I particularly wish to thank those who submitted their own
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implementations of this feature.
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</p>
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<h3><a name="whatsnew207">What's new in version 2.07?</a></h3>
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Per a suggestion by Geoff Mulligan, cgic now tolerates keys without a value in URL-encoded GET and POST submissions. Although the HTML5 spec discourages it, there are existing systems in the wild that do leave the `=` off entirely if the value is an empty string. Beginning with version 2.07, `cgic` handles this as you'd expect: you get an entry with the corresponding key and an empty string as the value. A simple unit test compilation target was also added, to test this feature and rule out side effects.
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<h3><a name="whatsnew206">What's new in version 2.06?</a></h3>
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A long list of significant fixes generously contributed by Jeffrey Hutzelman.
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<a href="https://github.com/boutell/cgic/commit/2065a2dfa480209bd6171acb2a4edd6e1c27a062"> These are especially important on platforms where attempting to read beyong the content length stated by the request can lead to a deadlock. Please see the commit notes.</a>
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<h3><a name="whatsnew205">What's new in version 2.05?</a></h3>
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Uploaded files properly closed; corrects a resource leak and enables
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file uploads to work properly on platforms with particular file
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locking semantics.
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<h3><a name="whatsnew204">What's new in version 2.04?</a></h3>
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Documentation fixes: the cgiHtmlEscape, cgiHtmlEscapeData,
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cgiValueEscape, and cgiValueEscapeData routines were named
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incorrectly in the manual. No code changes in version 2.04.
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<h3><a name="whatsnew203">What's new in version 2.03?</a></h3>
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<ul>
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<li>Support for setting cookies has been reimplemented. The new
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code closely follows the actual practice of web sites that successfully
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use cookies, rather than attempting to implement the specification.
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The new code can successfully set more than one cookie at a time in
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typical web browsers.
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</ul>
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<h3><a name="whatsnew202">What's new in version 2.02?</a></h3>
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<ul>
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<li>In CGIC 2.0 and 2.01, if the HTTP_COOKIE environment variable
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was exactly equal to the name of a cookie requested with cgiCookieString,
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with no value or equal sign or other characters present, a buffer
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overrun could take place. This was not normal behavior and it is
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unknown whether any actual web server would allow it to occur, however
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we have of course released a patch to correct it.
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Thanks to Nicolas Tomadakis.
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<li>cgiCookieString returned cgiFormTruncated when cgiFormSuccess would
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be appropriate. Fixed; thanks to Mathieu Villeneuve-Belair.
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<li>Cookies are now set using a simpler Set-Cookie: header, and with
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one header line per cookie, based on data collected by Chunfu Lai.
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<li>Memory leaks in cgiReadEnvironment fixed by Merezko Oleg. These
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memory leaks were <em>not</em> experienced in a normal CGI situation, only
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when reading a saved CGI environment.
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</ul>
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<h3><a name="whatsnew201">What's new in version 2.01?</a></h3>
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<ul>
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<li>Makefile supports "make install"
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<li>Compiles without warnings under both C and C++ with strict
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warnings and strict ANSI compliance enabled
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<li>Builds out of the box on Windows (#include <fcntl.h> was needed)
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<li>Rare problem in cgiReadEnvironment corrected; no impact on
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normal CGI operations
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<li>cgiCookieString now sets the result to an empty string
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when returning cgiFormNotFound
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<li>Minor code cleanups
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</ul>
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<h3><a name="whatsnew200">What's new in version 2.0?</a></h3>
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1. CGIC 2.0 provides support for file upload fields. User-uploaded
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files are kept in temporary files, to avoid the use of
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excessive swap space (Solaris users may wish to change the
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<code>cgicTempDir</code> macro in cgic.c before compiling).
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The <code><a href="#cgiFormFileName">cgiFormFileName</a></code>,
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<code><a href="#cgiFormFileContentType">cgiFormFileContentType</a></code>,
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<code><a href="#cgiFormFileSize">cgiFormFileSize</a></code>,
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<code><a href="#cgiFormFileOpen">cgiFormFileOpen</a></code>,
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<code><a href="#cgiFormFileRead">cgiFormFileRead</a></code>, and
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<code><a href="#cgiFormFileClose">cgiFormFileClose</a></code> functions
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provide a complete interface to this new functionality. Remember,
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the <code>enctype</code> attribute of the <code>form</code> tag
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must be set to <code>multipart/form-data</code> when
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<code><input type="file"></code> tags are used.
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<p>
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2. CGIC 2.0 provides support for setting and examining cookies
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(persistent data storage on the browser side).
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The <code><a href="#cgiCookieString">cgiCookieString</a></code>,
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and <code><a href="#cgiCookieInteger">cgiCookieInteger</a></code>
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and <code><a href="#cgiCookies">cgiCookies</a></code>
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functions retrieve cookies. The
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<code><a href="#cgiHeaderCookieSetString">cgiHeaderCookieSetString</a></code>
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and <code><a href="#cgiHeaderCookieSetInteger">cgiHeaderCookieSetInteger</a></code> functions set cookies.
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<p>
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3. CGIC 2.0 offers a convenient way to retrieve a list of all form fields.
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The new <code><a href="#cgiFormEntries">cgiFormEntries</a></code>
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function performs this operation.
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<p>
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4. CGIC 2.0 provides convenience functions to correctly escape
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text before outputting it as part of HTML, or as part of the
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value of a tag attribute, such as the <code>HREF</code> or
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<code>VALUE</code> attribute. See
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<code><a href="#cgiHtmlEscape">cgiHtmlEscape</a></code>,
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<code><a href="#cgiHtmlEscapeData">cgiHtmlEscapeData</a></code>,
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<code><a href="#cgiValueEscape">cgiValueEscape</a></code> and
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<code><a href="#cgiValueEscapeData">cgiValueEscapeData</a></code>.
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<p>
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5. Users have often asked the correct way to determine which submit
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button was clicked. This could always be accomplished in previous versions,
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but CGIC 2.0 also provides
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<a href="#cgiFormSubmitClicked">cgiFormSubmitClicked</a>,
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a convenient alternate label for the
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<a href="#cgiFormCheckboxSingle">cgiFormCheckboxSingle</a> function.
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<h3><a name="whatsnew107">What's new in version 1.07?</a></h3>
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A problem with the cgiFormString and related functions has been
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corrected. These functions were previously incorrectly returning cgiFormTruncated
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in cases where the returned string fit the buffer exactly.
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<h3><a name="whatsnew106">What's new in version 1.06?</a></h3>
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1. A potentially significant buffer overflow problem has been
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corrected. Jon Ribbens correctly pointed out to me (and to the
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Internet's bugtraq mailing list) that the cgiFormEntryString
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function, which is used directly or indirectly by almost all
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CGIC programs, can potentially write past the buffer passed
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to it by the programmer. This bug has been corrected.
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Upgrading to version 1.06 is <strong>strongly recommended.</strong>
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<P>
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2. The function <code>cgiSaferSystem()</code> has been
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removed entirely. This function escaped only a few metacharacters,
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while most shells have many, and there was no way to account for
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the many different operating system shells that might be in use
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on different operating systems. Since this led to a false sense
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of security, the function has been removed. It is our recommendation
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that user input should never be passed directly on the command line
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unless it has been carefully shown to contain only characters
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regarded as safe and appropriate by the programmer. Even then, it is
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better to design your utilities to accept their input from standard
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input rather than the command line.
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<h3><a name="whatsnew105">What's new in version 1.05?</a></h3>
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Non-exclusive commercial license fee reduced to $200.
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<h3><a name="whatsnew104">What's new in version 1.04?</a></h3>
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For consistency with other packages, the standard Makefile
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now produces a true library for cgic (libcgic.a).
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<h3><a name="whatsnew103">What's new in version 1.03?</a></h3>
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Version 1.03 sends line feeds only (ascii 10) to end
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Content-type:, Status:, and other HTTP protocol output lines,
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instead of CR/LF sequences. The standard specifies CR/LF.
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Unfortunately, too many servers reject CR/LF to make
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implementation of that standard practical. No server
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tested ever rejects LF alone in this context.
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<h3><a name="whatsnew102">What's new in version 1.02?</a></h3>
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Version 1.02 corrects bugs in previous versions:
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<ul>
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<li>
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<a href="#cgiFormDoubleBounded">cgiFormDoubleBounded</a> specified
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its arguments in the wrong order, with surprising results.
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This bug has been corrected.
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</ul>
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<h3><a name="whatsnew101">What's new in version 1.01?</a></h3>
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Version 1.01 adds no major functionality but corrects
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significant bugs and incompatibilities:
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<ul>
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<li>
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<a href="#cgiFormInteger">cgiFormInteger</a>,
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<a href="#cgiFormIntegerBounded">cgiFormIntegerBounded</a>,
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<a href="#cgiFormDouble">cgiFormDouble</a> and
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<a href="#cgiFormDoubleBounded">cgiFormDoubleBounded</a> now
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accept negative numbers properly. They also accept positive
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numbers with an explicit + sign.
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<li>Hex values containing the digit <code>9</code> are
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now properly decoded.
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<li><a href="#cgiFormString">cgiFormString</a> now
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represents each newline as a single line feed (ascii 10 decimal)
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as described in the documentation, not a carriage return
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(ascii 13 decimal) as in version 1.0. The latter approach
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pleased no one.
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<li><a href="#cgiFormString">cgiFormString</a> and
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<a href="#cgiFormStringNoNewlines">cgiFormStringNoNewlines</a>
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no longer erroneously return cgiFormEmpty in place of
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cgiFormSuccess.
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<li>The main() function of cgic now flushes standard output
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and sleeps for one second before exiting in order to inhibit
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problems with the completion of I/O on some platforms. This was
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not a cgic bug per se, but has been reported as a common problem
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with CGI when used with the CERN server. This change should
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improve compatibility.
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<li>The single selection example in the testform.html
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example now works properly. This was an error in the
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form itself, not cgic.
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<li><a href="#cgiRemoteUser">cgiRemoteUser</a> and
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<a href="#cgiRemoteIdent">cgiRemoteIdent</a> are now
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documented accurately. They were reversed earlier.
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</ul>
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<h3><a name="whatis">What is cgic?</a></h3>
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cgic is an ANSI C-language library for the creation of CGI-based
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World Wide Web applications. For basic information about
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the CGI standard, see the <a href="http://hoohoo.ncsa.uiuc.edu/cgi/">
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CGI documentation</a> at NCSA.
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<p>
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cgic performs the following tasks:
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<ul>
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<li>Parses form data, correcting for defective and/or inconsistent browsers
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<li>Transparently accepts both GET and POST form data
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<li>Accepts uploaded files as well as regular form fields
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<li>Provides functions to set and retrieve "cookies"
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(browser-side persistent information)
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<li>Handles line breaks in form fields in a consistent manner
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<li>Provides string, integer, floating-point, and single- and
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multiple-choice functions to retrieve form data
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<li>Provides bounds checking for numeric fields
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<li>Loads CGI environment variables into C strings which are always non-null
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<li>Provides a way to capture CGI situations for replay in a debugging
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environment, including file uploads and cookies
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</ul>
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<p>
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cgic is compatible with any CGI-compliant server environment, and
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compiles without modification in Posix/Unix/Linux and Windows
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environments.
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<h3><a name="obtain">Obtaining cgic</a></h3>
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cgic is distributed via the web in two forms: as a Windows-compatible
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.ZIP file, and as a gzipped tar file. Most users of Windows and
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related operating systems have access to 'unzip' or 'pkunzip'. All modern Unix
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systems come with 'gunzip' and 'tar' as standard equipment, and gzip/gunzip
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is not difficult to find if yours does not. Versions
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of these programs for other operating systems are widely
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available if you do not already have them.
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<p>
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<strong>Important:</strong> to use cgic, you will need an ANSI-standard
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C compiler. Under Unix, just obtain and use gcc. Most Unix systems have
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standardiszed on gcc. Users of Windows operating systems should not have
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ANSI C-related problems as all of the popular compilers follow the ANSI
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standard.
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<p>
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<strong>Note for Windows Programmers:</strong> you must use a modern
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32-bit compiler. Visual C++ 2.0 or higher, Borland C++ and the
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mingw32 gcc compiler are all appropriate, as is cygwin. Do
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<strong>NOT</strong> use an ancient 16-bit DOS executable compiler, please.
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<blockquote>
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<h4>What Operating System Does Your WEB SERVER Run?</h4>
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Remember, the computer on your desk is usually NOT your web server.
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Compiling a Windows console executable will not give you a CGI program that
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can be installed on a Linux-based server.
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</blockquote>
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<h3><a name="build">Building cgic: a sample application</a></h3>
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The sample application 'cgictest.c' is provided as part of the
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cgic distribution. This CGI program displays an input form,
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accepts a submission, and then displays what was submitted.
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In the process essentially all of cgic's features are tested.
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<p>
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On a Unix system, you can build cgictest simply by typing
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'make cgictest.cgi'. cgic.c and cgictest.c will be compiled and linked
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together to produce the cgictest application. Under non-Unix
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operating systems, you will need to create and compile an appropriate
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project containing the files cgic.c and cgictest.c.
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<p>
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<strong>IMPORTANT:</strong> after compiling cgictest.cgi, you will
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need to place it in a location on your server system which is
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designated by your server administrator as an appropriate location
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for CGI scripts. Some servers are configured to recognize any
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file ending in .cgi as a CGI program when it is found in any
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subdirectory of the server's web space, but this is not always
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the case! The right locations for CGI
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programs vary greatly from one server to another. Resolving
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this issue is between you, your web server administrator,
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and your web server documentation. Before submitting a bug
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report for cgic, make certain that the CGI example programs
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which came with your server <em>do</em> work for you. Otherwise
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it is very likely that you have a server configuration problem.
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<p>
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Once you have moved cgictest.cgi (or cgictest.exe, under Windows)
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to an appropriate cgi directory,
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use the web browser of your choice to access the URL at which
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you have installed it
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(for instance, <code>www.mysite.com/cgi-bin/cgictest.cgi</code>).
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Fill out the various fields in any manner you wish, then
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select the SUBMIT button.
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<p>
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If all goes well, cgictest.cgi will respond with a page which
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indicates the various settings you submitted. If not,
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please reread the section above regarding the correct location in
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which to install your CGI program on your web server.
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<h3><a name="nocompile">What to do if it won't compile</a></h3>
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<ul>
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<li><strong>Are you using Visual C++ or Borland C++? Did you forget to add
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cgic.c to your project?</strong>
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<li><strong>Make sure you are using an ANSI C or C++ compiler.</strong>
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(All of the Windows compilers are ANSI C compliant.)
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</ul>
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If none of the above proves effective, please see the
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section regarding <a href="#support">support</a>.
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<h3><a name="howto">How to write a cgic application</a></h3>
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<em>Note: </em> All cgic applications must be linked to the cgic.c module
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itself. How to do this depends on your operating system; under Unix,
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just use the provided Makefile as an example.
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<p>
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Since all CGI applications must perform certain initial
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tasks, such as parsing form data and examining
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environment variables, the cgic library provides its
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own main() function. When you write applications that
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use cgic, you will begin your own programs by writing
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a cgiMain() function, which cgic will invoke when
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the initial cgi work has been successfully completed. Your
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program must also be sure to #include the file cgic.h.
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<p>
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<strong>Important:</strong> if you write your own main()
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function, your program will not link properly. Your own
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code should begin with cgiMain(). The library
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provides main() for you. (Those who prefer different behavior
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can easily modify cgic.c.)
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<p>
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Consider the cgiMain function of cgictest.c:
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<p>
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<PRE>
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int cgiMain() {
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#ifdef DEBUG
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LoadEnvironment();
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#endif /* DEBUG */
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/* Load a previously saved CGI scenario if that button
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has been pressed. */
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if (cgiFormSubmitClicked("loadenvironment") == cgiFormSuccess) {
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LoadEnvironment();
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}
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/* Set any new cookie requested. Must be done *before*
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outputting the content type. */
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CookieSet();
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/* Send the content type, letting the browser know this is HTML */
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cgiHeaderContentType("text/html");
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/* Top of the page */
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fprintf(cgiOut, "<HTML><HEAD>\n");
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fprintf(cgiOut, "<TITLE>cgic test</TITLE></HEAD>\n");
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fprintf(cgiOut, "<BODY><H1>cgic test</H1>\n");
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/* If a submit button has already been clicked, act on the
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submission of the form. */
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if ((cgiFormSubmitClicked("testcgic") == cgiFormSuccess) ||
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cgiFormSubmitClicked("saveenvironment") == cgiFormSuccess)
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{
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HandleSubmit();
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fprintf(cgiOut, "<hr>\n");
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}
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/* Now show the form */
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ShowForm();
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/* Finish up the page */
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fprintf(cgiOut, "</BODY></HTML>\n");
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return 0;
|
|
}
|
|
</PRE>
|
|
Note the DEBUG #ifdef. If DEBUG is defined at compile time, either by
|
|
inserting the line "#define DEBUG 1" into the program or by setting
|
|
it in the Makefile or other development environment, then the
|
|
LoadEnvironment function is invoked. This function calls
|
|
<a href="#cgiReadEnvironment">cgiReadEnvironment()</a>
|
|
to restore a captured CGI environment for debugging purposes. See
|
|
also the discussion of the <a href="#debug">capture</a> program, which is
|
|
provided for use in CGI debugging. Because this is a test program,
|
|
the <a href="#cgiFormSubmitClicked">cgiFormSubmitClicked</a> function is
|
|
also called to check for the use of a button that requests the reloading
|
|
of a saved CGI environment. A completed CGI program typically would
|
|
never allow the end user to make that decision.
|
|
<h4>Setting Cookies</h4>
|
|
Next, one of the cgiHeader functions should be called.
|
|
This particular program demonstrates many features, including
|
|
the setting of cookies. If the programmer wishes to set a cookie,
|
|
the cookie-setting function must be called
|
|
first, before other headers are output. This is done by the
|
|
CookieSet() function of cgictest.c:
|
|
<pre>
|
|
void CookieSet()
|
|
{
|
|
char cname[1024];
|
|
char cvalue[1024];
|
|
/* Must set cookies BEFORE calling
|
|
cgiHeaderContentType */
|
|
cgiFormString("cname", cname, sizeof(cname));
|
|
cgiFormString("cvalue", cvalue, sizeof(cvalue));
|
|
if (strlen(cname)) {
|
|
/* Cookie lives for one day (or until
|
|
browser chooses to get rid of it, which
|
|
may be immediately), and applies only to
|
|
this script on this site. */
|
|
cgiHeaderCookieSet(cname, cvalue,
|
|
86400, cgiScriptName, cgiServerName,
|
|
cgiCookieHttpOnly | cgiCookieSameSiteStrict);
|
|
}
|
|
}
|
|
</pre>
|
|
Since this is a test program, the <a href="#cgiFormString">cgiFormString</a>
|
|
function is used to fetch the name and value from the form previously filled
|
|
in by the user. Normally, cookie names and values are chosen to meet the
|
|
needs of the programmer and provide a means of identifying the same
|
|
user again later.
|
|
<p>
|
|
The <a href="#cgiHeaderCookieSet">cgiHeaderCookieSet</a>
|
|
function sets the cookie by requesting that the web browser store it.
|
|
<strong>There is never any guarantee that this will happen!</strong>
|
|
Many browsers reject cookies completely; others do not necessarily keep
|
|
them as long as requested or return them with their values intact.
|
|
Always code defensively when using cookies.
|
|
<p>
|
|
The cname and cvalue parameters are of course the namd and value for
|
|
the cookie. The third argument is the time, in seconds, that the
|
|
cookie should "live" on the browser side before it expires; in this
|
|
case it has been set to 86,400 seconds, which is exactly one day.
|
|
<strong>The browser may or may not respect this setting, as with everything
|
|
else about cookies.</strong>
|
|
<p>
|
|
The fourth argument identifies the "path" within the web site for which
|
|
the cookie is considered valid. A cookie that should be sent back
|
|
for every access to the site should be set with a path of <code>/</code>.
|
|
In this case the cookie is relevant only to the CGI program itself, so
|
|
<code><a href="#cgiScriptName">cgiScriptName</a></code> (the URL of the CGI program, not including the
|
|
domain name) is sent. Similarly, a cookie can be considered relevant
|
|
to a single web site or to an entire domain, such as
|
|
<code>www.boutell.dev</code> or the entire <code>.boutell.dev</code>
|
|
domain. In this case, the current site on which the program is running
|
|
is the only relevant site, so <code><a href="#cgiServerName">cgiServerName</a></code> is used
|
|
as the domain.
|
|
<p>
|
|
The sixth argument sets extra security options, for example <i>HttpOnly</i> or
|
|
<i>SameSite=Strict</i> to prevent cross-site-scripting attacks.
|
|
<h4>Outputting the Content Type Header</h4>
|
|
Next, <a href="#cgiHeaderContentType">cgiHeaderContentType()</a> is
|
|
called to indicate the MIME type of the document being output, in this case
|
|
"text/html" (a normal HTML document). A few other common MIME types are
|
|
"image/gif", "image/jpeg" and "audio/wav".
|
|
<p>
|
|
Note that <a href="#cgiHeaderStatus">cgiHeaderStatus()</a> or
|
|
<a href="#cgiHeaderLocation">cgiHeaderLocation()</a> could have
|
|
been invoked instead to output an error code or redirect the
|
|
request to a different URL. Only one of the cgiHeader functions
|
|
should be called in a single execution of the program.
|
|
<p>
|
|
<strong>Important:</strong> one of the cgiHeader functions,
|
|
usually <a href="#cgiHeaderContentType">cgiHeaderContentType()</a>,
|
|
<em>must</em> be invoked before outputting any other
|
|
response to the user. Otherwise, the result will not be a valid
|
|
document and the browser's behavior will be unpredictable.
|
|
You may, of course, output your own ContentType and other
|
|
header information to <a href="#cgiOut">cgiOut</a> if you prefer. The cgiHeader functions
|
|
are provided as a convenience.
|
|
<h4>Handling Form Submissions</h4>
|
|
Like many CGI programs, cgictest makes decisions about the way it
|
|
should behave based on whether various submit buttons have been clicked.
|
|
When either the testcgic or saveenvironment button is present, cgictest
|
|
invokes the HandleSubmit function, which invokes additional functions to
|
|
handle various parts of the form:
|
|
<pre>
|
|
void HandleSubmit()
|
|
{
|
|
Name();
|
|
Address();
|
|
Hungry();
|
|
Temperature();
|
|
Frogs();
|
|
Color();
|
|
Flavors();
|
|
NonExButtons();
|
|
RadioButtons();
|
|
File();
|
|
Entries();
|
|
Cookies();
|
|
/* The saveenvironment button, in addition to submitting
|
|
the form, also saves the resulting CGI scenario to
|
|
disk for later replay with the 'load saved environment'
|
|
button. */
|
|
if (cgiFormSubmitClicked("saveenvironment") == cgiFormSuccess) {
|
|
SaveEnvironment();
|
|
}
|
|
}
|
|
</pre>
|
|
<h4>Handling Text Input</h4>
|
|
The Name() function of cgictest is shown below, in its simplest
|
|
possible form:
|
|
<PRE>
|
|
void Name() {
|
|
char name[81];
|
|
<a href="#cgiFormStringNoNewlines">cgiFormStringNoNewlines</a>("name", name, 81);
|
|
fprintf(cgiOut, "Name: ");
|
|
cgicHtmlEscape(name);
|
|
fprintf(cgiOut, "<BR>\n");
|
|
}
|
|
</PRE>
|
|
The purpose of this function is to retrieve and display the name that was
|
|
input by the user. Since the programmer has decided that names should
|
|
be permitted to have up to 80 characters, a buffer of 81 characters
|
|
has been declared (allowing for the final null character).
|
|
The <a href="#cgiFormStringNoNewlines">cgiFormStringNoNewlines()</a>
|
|
function is then invoked to retrieve the name and ensure that
|
|
carriage returns are not present in the name (despite the
|
|
incorrect behavior of some web browsers). The first argument
|
|
is the name of the input field in the form, the second argument
|
|
is the buffer to which the data should be copied, and the third
|
|
argument is the size of the buffer. cgic will never write beyond
|
|
the size of the buffer, and will always provide a null-terminated
|
|
string in response; if the buffer is too small, the string will
|
|
be shortened. If this is not acceptable, the
|
|
<a href="#cgiFormStringSpaceNeeded">cgiFormStringSpaceNeeded()</a>
|
|
function can be used to check the amount of space needed; the
|
|
return value of cgiFormStringNoNewlines() can also be checked
|
|
to determine whether truncation occurred. See
|
|
the full description of <a href="#cgiFormStringNoNewlines">
|
|
cgiFormStringNoNewlines()</a>.
|
|
<h4>Handling Output</h4>
|
|
Note that Name() writes its HTML output to <a href="#cgiOut">cgiOut</a>, not
|
|
to stdout.
|
|
<p>
|
|
The actual name submitted by the user may or may not contain
|
|
characters that have special meaning in HTML, specifically the
|
|
the <code><</code>, <code>></code>, and <code>&</code> characters.
|
|
The <a href="#cgiHtmlEscape">cgiHtmlEscape</a> function is used to output
|
|
the user-entered name with any occurrences of these characters
|
|
correctly escaped as <code>&lt;</code>, <code>&gt;</code>,
|
|
and <code>&amp;</code>.
|
|
<p>
|
|
<strong>Important:</strong> <a href="#cgiOut">cgiOut</a> is normally equivalent
|
|
to stdout, and there is no performance penalty for using it.
|
|
It is recommended that you write output to <a href="#cgiOut">cgiOut</a> to ensure compatibility
|
|
with modified versions of the cgic library for special
|
|
environments that do not provide stdin and stdout for
|
|
each cgi connection.
|
|
<p>
|
|
Note that, for text input areas in which carriage returns <em>are</em>
|
|
desired, the function <a href="#cgiFormString">cgiFormString</a>
|
|
should be used instead. cgiFormString ensures that line breaks
|
|
are always represented by a single carriage return (ascii decimal 13),
|
|
making life easier for the programmer. See the source code to
|
|
the Address() function of cgictest.c for an example.
|
|
<h4>Handling Single Checkboxes</h4>
|
|
Consider the Hungry() function, which determines whether
|
|
the user has selected the "hungry" checkbox:
|
|
<PRE>
|
|
void Hungry() {
|
|
if (<a href="#cgiFormCheckboxSingle">cgiFormCheckboxSingle</a>("hungry") == <a href="#cgiFormSuccess">cgiFormSuccess</a>) {
|
|
fprintf(cgiOut, "I'm Hungry!<BR>\n");
|
|
} else {
|
|
fprintf(cgiOut, "I'm Not Hungry!<BR>\n");
|
|
}
|
|
}
|
|
</PRE>
|
|
This function takes advantage of the
|
|
<a href="#cgiFormCheckboxSingle">cgiFormCheckboxSingle()</a> function, which
|
|
determines whether a single checkbox has been selected.
|
|
cgiFormCheckboxSingle() accepts the name attribute of the checkbox
|
|
as its sole argument and returns <a href="#cgiFormSuccess">
|
|
cgiFormSuccess</a> if the checkbox is selected, or
|
|
<a href="#cgiFormNotFound">cgiFormNotFound</a> if it is not.
|
|
If multiple checkboxes with the same name are in use,
|
|
consider the <a href="#cgiFormCheckboxMultiple">
|
|
cgiFormCheckboxMultiple()</a> and
|
|
<a href="#cgiFormStringMultiple">cgiFormStringMultiple()</a>
|
|
functions.
|
|
<h4>Handling Numeric Input</h4>
|
|
Now consider the Temperature() function, which retrieves
|
|
a temperature in degrees (a floating-point value) and ensures
|
|
that it lies within particular bounds:
|
|
<PRE>
|
|
void Temperature() {
|
|
double temperature;
|
|
<a href="#cgiFormDoubleBounded">cgiFormDoubleBounded</a>("temperature", &temperature, 80.0, 120.0, 98.6);
|
|
fprintf(<a href="#cgiOut">cgiOut</a>, "My temperature is %f.<BR>\n", temperature);
|
|
}
|
|
</PRE>
|
|
The temperature is retrieved by the function
|
|
<a href="#cgiFormDoubleBounded">cgiFormDoubleBounded()</a>. The first
|
|
argument is the name of the temperature input field in the form;
|
|
the second argument points to the address of the variable that will
|
|
contain the result. The next two arguments are the lower and upper
|
|
bounds, respectively. The final argument is the default value to
|
|
be returned if the user did not submit a value.
|
|
<p>
|
|
This function always retrieves a reasonable value within the
|
|
specified bounds; values above or below bounds are constrained
|
|
to fit the bounds. However, the return value of
|
|
cgiFormDoubleBounded can be checked to make sure the
|
|
actual user entry was in bounds, not blank, and so forth;
|
|
see the description of <a href="#cgiFormDoubleBounded">
|
|
cgiFormDoubleBounded()</a> for more details. If bounds checking
|
|
is not desired, consider using <a href="#cgiFormDouble">
|
|
cgiFormDouble()</a> instead.
|
|
<p>
|
|
Note that, for integer input, the functions
|
|
<a href="#cgiFormInteger">cgiFormInteger</a> and
|
|
<a href="#cgiFormIntegerBounded">cgiFormIntegerBounded</a>
|
|
are available. The behavior of these functions is similar to
|
|
that of their floating-point counterparts above.
|
|
<h4>Handling Single-Choice Input</h4>
|
|
The <SELECT> tag of HTML is used to provide the user with
|
|
several choices. Radio buttons and checkboxes can also be used
|
|
when the number of choices is relatively small. Consider
|
|
the Color() function of cgictest.c:
|
|
<PRE>
|
|
char *colors[] = {
|
|
"Red",
|
|
"Green",
|
|
"Blue"
|
|
};
|
|
|
|
void Color() {
|
|
int colorChoice;
|
|
<a href="#cgiFormSelectSingle">cgiFormSelectSingle</a>("colors", colors, 3, &colorChoice, 0);
|
|
fprintf(<a href="#cgiOut">cgiOut</a>, "I am: %s<BR>\n", colors[colorChoice]);
|
|
}
|
|
</PRE>
|
|
This function determines which of several colors the user chose
|
|
from a <SELECT> list in the form. An array of colors is
|
|
declared; the <a href="#cgiFormSelectSingle">cgiFormSelectSingle()</a>
|
|
function is then invoked to determine which, if any, of those choices
|
|
was selected. The first argument indicates the name of the input
|
|
field in the form. The second argument points to the list of
|
|
acceptable colors. The third argument indicates the number of
|
|
entries in the color array. The fourth argument points to the
|
|
variable which will accept the chosen color, and the last argument
|
|
indicates the index of the default value to be set if no
|
|
selection was submitted by the browser.
|
|
<p>
|
|
<a href="#cgiFormSelectSingle">cgiFormSelectSingle()</a> will
|
|
always indicate a reasonable selection value. However, if
|
|
the programmer wishes to know for certain that a value was
|
|
actually submitted, that the value submitted was a legal
|
|
response, and so on, the return value of cgiFormSelectSingle()
|
|
can be consulted. See the full description of
|
|
<a href="#cgiFormSelectSingle">cgiFormSelectSingle()</a> for
|
|
more information.
|
|
<p>
|
|
Note that radio button groups and <SELECT> lists can both
|
|
be handled by this function. If you are processing radio
|
|
button groups, you may prefer to invoke
|
|
<a href="#cgiFormRadio">cgiFormRadio()</a>, which functions
|
|
identically.
|
|
<p>
|
|
<em>"What if I won't know the acceptable choices at runtime?"</em>
|
|
<p>
|
|
If the acceptable choices aren't known <em>until</em> runtime,
|
|
one can simply load the choices from disk. But if the acceptable
|
|
choices aren't fixed at all (consider a list of country names;
|
|
new names may be added to the form at any time and it is
|
|
inconvenient to also update program code or a separate list
|
|
of countries), simply invoke
|
|
<a href="#cgiFormStringNoNewlines">cgiFormStringNoNewlines()</a>
|
|
instead to retrieve the string directly. Keep in mind that, if
|
|
you do so, validating the response to make sure it is
|
|
safe and legitimate becomes a problem for your own
|
|
program to solve. The advantage of cgiFormSelectSingle() is that invalid
|
|
responses are never returned.
|
|
<p>
|
|
To handle multiple-selection <SELECT> lists and
|
|
groups of checkboxes with the same name, see the
|
|
discussion of the NonExButtons() function of cgictest.c, immediately below.
|
|
<h4>Handling Multiple-Choice Input</h4>
|
|
Consider the first half of the NonExButtons() function of cgictest.c:
|
|
<PRE>
|
|
char *votes[] = {
|
|
"A",
|
|
"B",
|
|
"C",
|
|
"D"
|
|
};
|
|
|
|
void NonExButtons() {
|
|
int voteChoices[4];
|
|
int i;
|
|
int result;
|
|
int invalid;
|
|
|
|
char **responses;
|
|
|
|
/* Method #1: check for valid votes. This is a good idea,
|
|
since votes for nonexistent candidates should probably
|
|
be discounted... */
|
|
fprintf(<a href="#cgiOut">cgiOut</a>, "Votes (method 1):<BR>\n");
|
|
result = <a href="#cgiFormCheckboxMultiple">cgiFormCheckboxMultiple</a>("vote", votes, 4,
|
|
voteChoices, &invalid);
|
|
if (result == <a href="#cgiFormNotFound">cgiFormNotFound</a>) {
|
|
fprintf(<a href="#cgiOut">cgiOut</a>, "I hate them all!<p>\n");
|
|
} else {
|
|
fprintf(<a href="#cgiOut">cgiOut</a>, "My preferred candidates are:\n");
|
|
fprintf(<a href="#cgiOut">cgiOut</a>, "<ul>\n");
|
|
for (i=0; (i < 4); i++) {
|
|
if (voteChoices[i]) {
|
|
fprintf(<a href="#cgiOut">cgiOut</a>, "<li>%s\n", votes[i]);
|
|
}
|
|
}
|
|
fprintf(<a href="#cgiOut">cgiOut</a>, "</ul>\n");
|
|
}
|
|
</PRE>
|
|
This function takes advantage of
|
|
<a href="#cgiFormCheckboxMultiple">cgiFormCheckboxMultiple()</a>,
|
|
which is used to identify one or more selected checkboxes with
|
|
the same name. This function performs identically to
|
|
<a href="#cgiFormSelectMultiple">cgiFormSelectMultiple()</a>.
|
|
That is, <SELECT> tags with the MULTIPLE attribute are handled
|
|
just like a group of several checkboxes with the same name.
|
|
<p>
|
|
The first argument to <a href="#cgiFormCheckboxMultiple">
|
|
cgiFormCheckboxMultiple()</a> is the name given to all
|
|
checkbox input fields in the group. The second argument
|
|
points to an array of legitimate values; these should
|
|
correspond to the VALUE attributes of the checkboxes
|
|
(or OPTION tags in a <SELECT> list). The third argument
|
|
indicates the number of entries in the array of
|
|
legitimate values. The fourth argument points to
|
|
an array of integers with the same number of entries
|
|
as the array of legitimate values; each entry
|
|
will be set true if that checkbox or option was selected,
|
|
false otherwise.
|
|
<p>
|
|
The last argument points to an integer which will be set to the
|
|
number of invalid responses (responses not in the array of
|
|
valid responses) that were submitted. If this value is not
|
|
of interest, the last argument may be a null pointer (0).
|
|
<p>
|
|
Note that the return value of cgiFormCheckboxMultiple is
|
|
inspected to determine whether any choices at all were
|
|
set. See the full description of
|
|
<a href="#cgiFormCheckboxMultiple">cgiFormCheckboxMultiple</a>
|
|
for other possible return values.
|
|
<p>
|
|
<em>"What if I won't know the acceptable choices at runtime?"</em>
|
|
<p>
|
|
If the acceptable choices aren't known <em>until</em> runtime,
|
|
one can simply load the choices from disk. But if the acceptable
|
|
choices aren't fixed at all (consider a list of ice cream flavors;
|
|
new names may be added to the form at any time and it is
|
|
inconvenient to also update program code or a separate list
|
|
of countries), a more dynamic approach is needed. Consider
|
|
the second half of the NonExButtons() function of cgictest.c:
|
|
<PRE>
|
|
/* Method #2: get all the names voted for and trust them.
|
|
This is good if the form will change more often
|
|
than the code and invented responses are not a danger
|
|
or can be checked in some other way. */
|
|
fprintf(<a href="#cgiOut">cgiOut</a>, "Votes (method 2):<BR>\n");
|
|
result = <a href="#cgiFormStringMultiple">cgiFormStringMultiple</a>("vote", &responses);
|
|
if (result == <a href="#cgiFormNotFound">cgiFormNotFound</a>) {
|
|
fprintf(<a href="#cgiOut">cgiOut</a>, "I hate them all!<p>\n");
|
|
} else {
|
|
int i = 0;
|
|
fprintf(<a href="#cgiOut">cgiOut</a>, "My preferred candidates are:\n");
|
|
fprintf(<a href="#cgiOut">cgiOut</a>, "<ul>\n");
|
|
while (responses[i]) {
|
|
fprintf(<a href="#cgiOut">cgiOut</a>, "<li>%s\n", responses[i]);
|
|
i++;
|
|
}
|
|
fprintf(<a href="#cgiOut">cgiOut</a>, "</ul>\n");
|
|
}
|
|
/* We must be sure to free the string array or a memory
|
|
leak will occur. Simply calling free() would free
|
|
the array but not the individual strings. The
|
|
function cgiStringArrayFree() does the job completely. */
|
|
<A HREF="#cgiStringArrayFree">cgiStringArrayFree</a>(responses);
|
|
}
|
|
</PRE>
|
|
This code excerpt demonstrates an alternate means of retrieving
|
|
a list of choices. The function
|
|
<a href="#cgiFormStringMultiple">cgiFormStringMultiple()</a> is used
|
|
to retrieve an array consisting of all the strings submitted
|
|
for with a particular input field name. This works both for
|
|
<SELECT> tags with the MULTIPLE attribute and for
|
|
groups of checkboxes with the same name.
|
|
<P>
|
|
The first argument to <a href="#cgiFormStringMultiple">
|
|
cgiFormStringMultiple()</a> is the name of the input field or
|
|
group of input fields in question. The second argument should
|
|
be the address of a pointer to a pointer to a string, which
|
|
isn't as bad as it sounds. Consider the following simple call
|
|
of the function:
|
|
<PRE>
|
|
/* An array of strings; each C string is an array of characters */
|
|
char **responses;
|
|
|
|
<a href="#cgiFormStringMultiple">cgiFormStringMultiple</a>("vote", &responses);
|
|
</PRE>
|
|
<em>"How do I know how many responses there are?"</em>
|
|
<p>
|
|
After the call, the last entry in the string array will be
|
|
a null pointer. Thus the simple loop:
|
|
<PRE>
|
|
int i = 0;
|
|
while (responses[i]) {
|
|
/* Do something with the string responses[i] */
|
|
i++;
|
|
}
|
|
</PRE>
|
|
can be used to walk through the array until the last
|
|
entry is encountered.
|
|
<p>
|
|
<strong>Important:</strong> the
|
|
<a href="#cgiFormStringMultiple">cgiFormStringMultiple</a> function
|
|
returns a pointer to <strong>allocated memory</strong>. Your code
|
|
should not modify the strings in the responses array or the responses
|
|
array itself; if modification is needed, the strings should be
|
|
copied. When your code is done examining the responses array,
|
|
you <strong>MUST</strong> call <a href="#cgiStringArrayFree">
|
|
cgiStringArrayFree()</a> with the array as an argument to free the memory
|
|
associated with the array. Otherwise, the memory will not be available
|
|
again until the program exists. <strong>Don't</strong> just call the
|
|
free() function; if you do, the individual strings will not be freed.
|
|
<h4>Accessing Uploaded Files</h4>
|
|
CGIC provides functions to access files that have been uploaded
|
|
as part of a form submission. <strong>IMPORTANT: you MUST</strong> set
|
|
the <code>enctype</code> attribute of your <code>form</code> tag
|
|
to <code>multipart/form-data</code> for this feature to work! For an
|
|
example, see the <a href="#ShowForm">ShowForm</a> function of
|
|
cgictest.c, examined below.
|
|
<p>
|
|
The <code>File</code> function of cgictest.c takes care of
|
|
receiving uploaded files:
|
|
<pre>
|
|
void File()
|
|
{
|
|
cgiFilePtr file;
|
|
char name[1024];
|
|
char contentType[1024];
|
|
char buffer[1024];
|
|
int size;
|
|
int got;
|
|
if (cgiFormFileName("file", name, sizeof(name)) !=
|
|
cgiFormSuccess)
|
|
{
|
|
printf("<p>No file was uploaded.<p>\n");
|
|
return;
|
|
}
|
|
fprintf(cgiOut, "The filename submitted was: ");
|
|
cgiHtmlEscape(name);
|
|
fprintf(cgiOut, "<p>\n");
|
|
cgiFormFileSize("file", &size);
|
|
fprintf(cgiOut, "The file size was: %d bytes<p>\n", size);
|
|
cgiFormFileContentType("file", contentType, sizeof(contentType));
|
|
fprintf(cgiOut, "The alleged content type of the file was: ");
|
|
cgiHtmlEscape(contentType);
|
|
fprintf(cgiOut, "<p>\n");
|
|
fprintf(cgiOut, "Of course, this is only the claim the browser "
|
|
"made when uploading the file. Much like the filename, "
|
|
"it cannot be trusted.<p>\n");
|
|
fprintf(cgiOut, "The file's contents are shown here:<p>\n");
|
|
if (cgiFormFileOpen("file", &file) != cgiFormSuccess) {
|
|
fprintf(cgiOut, "Could not open the file.<p>\n");
|
|
return;
|
|
}
|
|
fprintf(cgiOut, "<pre>\n");
|
|
while (cgiFormFileRead(file, buffer, sizeof(buffer), &got) ==
|
|
cgiFormSuccess)
|
|
{
|
|
cgiHtmlEscapeData(buffer, got);
|
|
}
|
|
fprintf(cgiOut, "</pre>\n");
|
|
cgiFormFileClose(file);
|
|
}
|
|
</pre>
|
|
First, the File function checks to determine the filename that was
|
|
submitted by the user. <strong>VERY IMPORTANT: this filename may or
|
|
may not bear any relation to the real name of the file on the user's
|
|
computer, may be deliberately manipulated with malicious intent,</strong>
|
|
and should not be used for <strong>any</strong> purpose unless you have
|
|
determined that its content is safe for your intended use and will not,
|
|
at the very least, overwrite another file of importance to you, especially if
|
|
you intend to use it as a file name on the server side. The cgic library
|
|
itself does not use this file name for temporary storage.
|
|
<p>
|
|
If the <a href="#cgiFormFileName">cgiFormFileName</a> function does
|
|
not succeed, no file was uploaded.
|
|
<p>
|
|
Next, the <a href="#cgiFormFileSize">cgiFormFileSize</a> function is called
|
|
to determine the size of the uploaded file, in bytes.
|
|
<p>
|
|
The File function then proceeds to query the content type of the uploaded
|
|
file. Files uploaded by the user have their own content type information,
|
|
which may be useful in determining whether the file is an image, HTML document,
|
|
word processing document, or other type of file. However,
|
|
<strong>as with the filename and any other claim made by the browser,
|
|
this information should not be blindly trusted.</strong> The browser
|
|
may upload a file with the name <code>picture.jpg</code> and the
|
|
content type <code>image/jpeg</code>, but this does not guarantee that the
|
|
actual file will contain a valid JPEG image suitable for display.
|
|
<p>
|
|
The content type submitted by the browser can be queried using the
|
|
<a href="#cgiFormFileContentType">cgiFormFileContentType</a> function.
|
|
<p>
|
|
Of course, CGIC also provides access to the actual uploded file.
|
|
First, the programmer calls <a href="#cgiFormFileOpen">cgiFormFileOpen</a>,
|
|
passing the address of a <code>cgiFilePtr</code> object. If this function
|
|
succeeds, the <code>cgiFilePtr</code> object becomes valid, and can be
|
|
used in subsequent calls to <a href="#cgiFormFileRead">cgiFormFileRead</a>.
|
|
Notice that the number of bytes read may be less than the number requested,
|
|
in particular on the last successful call before cgiFormFileRead begins
|
|
to return <code>cgiFormEOF</code>. When cgiFormFileRead no longer returns
|
|
cgiFormSuccess,
|
|
the programmer calls <a href="#cgiFormClose">cgiFormFileClose</a> to
|
|
release the <code>cgiFilePtr</code> object.
|
|
<p>
|
|
The uploaded file data may contain anything, including binary data,
|
|
null characters, and so on. The example program uses the
|
|
<a href="#cgiHtmlEscapeData">cgiHtmlEscapeData</a> function to output the
|
|
data with any special characters that have meaning in HTML escaped.
|
|
Most programs will save the uploaded information to a server-side file or
|
|
database.
|
|
<h4>Fetching All Form Entries</h4>
|
|
From time to time, the programmer may not know the names of all
|
|
form fields in advance. In such situations it is convenient to
|
|
use the <a href="#cgiFormEntries">cgiFormEntries</a> function.
|
|
The Entries function of cgictest.c demonstrates the use of
|
|
cgiFormEntries:
|
|
<pre>
|
|
void Entries()
|
|
{
|
|
char **array, **arrayStep;
|
|
fprintf(cgiOut, "List of All Submitted Form Field Names:<p>\n");
|
|
if (cgiFormEntries(&array) != cgiFormSuccess) {
|
|
return;
|
|
}
|
|
arrayStep = array;
|
|
fprintf(cgiOut, "<ul>\n");
|
|
while (*arrayStep) {
|
|
fprintf(cgiOut, "<li>");
|
|
cgiHtmlEscape(*arrayStep);
|
|
fprintf(cgiOut, "\n");
|
|
arrayStep++;
|
|
}
|
|
fprintf(cgiOut, "</ul>\n");
|
|
cgiStringArrayFree(array);
|
|
}
|
|
</pre>
|
|
The cgiFormEntries function retrieves an array of form field names.
|
|
This array consists of pointers to strings, with a final null pointer
|
|
to mark the end of the list. The above code illustrates one way of
|
|
looping through the returned strings. Note the final call to
|
|
<a href="#cgiStringArrayFree">cgiStringArrayFree</a>, which is
|
|
essential in order to return the memory used to store the strings
|
|
and the string array.
|
|
<h4>Retrieving Cookies</h4>
|
|
The Cookies function of cgictest.c displays a list of all cookies
|
|
submitted by the browser with the current form submission, along
|
|
with their values:
|
|
<pre>
|
|
void Cookies()
|
|
{
|
|
char **array, **arrayStep;
|
|
char cname[1024], cvalue[1024];
|
|
fprintf(cgiOut, "Cookies Submitted On This Call, With Values "
|
|
"(Many Browsers NEVER Submit Cookies):<p>\n");
|
|
if (cgiCookies(&array) != cgiFormSuccess) {
|
|
return;
|
|
}
|
|
arrayStep = array;
|
|
fprintf(cgiOut, "<table border=1>\n");
|
|
fprintf(cgiOut, "<tr><th>Cookie<th>Value</tr>\n");
|
|
while (*arrayStep) {
|
|
char value[1024];
|
|
fprintf(cgiOut, "<tr>");
|
|
fprintf(cgiOut, "<td>");
|
|
cgiHtmlEscape(*arrayStep);
|
|
fprintf(cgiOut, "<td>");
|
|
cgiCookieString(*arrayStep, value, sizeof(value));
|
|
cgiHtmlEscape(value);
|
|
fprintf(cgiOut, "\n");
|
|
arrayStep++;
|
|
}
|
|
fprintf(cgiOut, "</table>\n");
|
|
cgiFormString("cname", cname, sizeof(cname));
|
|
cgiFormString("cvalue", cvalue, sizeof(cvalue));
|
|
if (strlen(cname)) {
|
|
fprintf(cgiOut, "New Cookie Set On This Call:<p>\n");
|
|
fprintf(cgiOut, "Name: ");
|
|
cgiHtmlEscape(cname);
|
|
fprintf(cgiOut, "Value: ");
|
|
cgiHtmlEscape(cvalue);
|
|
fprintf(cgiOut, "<p>\n");
|
|
fprintf(cgiOut, "If your browser accepts cookies "
|
|
"(many do not), this new cookie should appear "
|
|
"in the above list the next time the form is "
|
|
"submitted.<p>\n");
|
|
}
|
|
cgiStringArrayFree(array);
|
|
}
|
|
</pre>
|
|
<strong>VERY IMPORTANT: YOUR BROWSER MIGHT NOT SUBMIT COOKIES,
|
|
EVER, REGARDLESS OF WHAT VALUES YOU ENTER INTO THE TEST FORM.</strong>
|
|
Many, many browsers are configured not to accept or send cookies;
|
|
others are configured to send them as little as possible to meet the
|
|
bare minimum requirements for entry into popular sites. Users will often
|
|
refuse your cookies; make sure your code still works in that situation!
|
|
<p>
|
|
The above code uses the <a href="#cgiCookies">cgiCookies</a> function
|
|
to retrieve a list of all currently set cookies as a null-terminated
|
|
array of strings. The <a href="#cgiCookieString">cgiCookieString</a>
|
|
function is then used to fetch the value associated with each cookie;
|
|
this function works much like <a href="#cgiFormString">cgiFormString</a>,
|
|
discussed earlier. Note that a cookie set as a part of the current
|
|
form submission process does not appear on this list immediately, as
|
|
it has not yet been sent back by the browser. It should appear on
|
|
future submissions, provided that the browser chooses to accept
|
|
and resend the cookie at all.
|
|
<h4>Displaying a Form That Submits to the Current Program</h4>
|
|
CGI programmers often need to display HTML pages as part of the output
|
|
of CGI programs; these HTML pages often contain forms which should submit
|
|
fields back to the same program they came from. Provided that your
|
|
web server is well-configured, this can be done conveniently using
|
|
the cgiScriptName environment variable, as shown below. Here is the
|
|
source code of the ShowForm function of cgictest.c:
|
|
<pre>
|
|
void ShowForm()
|
|
{
|
|
fprintf(cgiOut, "<!-- 2.0: multipart/form-data is required
|
|
"for file uploads. -->");
|
|
fprintf(cgiOut, "<form method=\"POST\" "
|
|
"enctype=\"multipart/form-data\" ");
|
|
fprintf(cgiOut, " action=\"");
|
|
cgiValueEscape(cgiScriptName);
|
|
fprintf(cgiOut, "\">\n");
|
|
fprintf(cgiOut, "<p>\n");
|
|
fprintf(cgiOut, "Text Field containing Plaintext\n");
|
|
fprintf(cgiOut, "<p>\n");
|
|
fprintf(cgiOut, "<input type=\"text\" name=\"name\">Your Name\n");
|
|
fprintf(cgiOut, "<p>\n");
|
|
fprintf(cgiOut, "Multiple-Line Text Field\n");
|
|
fprintf(cgiOut, "<p>\n");
|
|
fprintf(cgiOut, "<textarea NAME=\"address\" ROWS=4 COLS=40>\n");
|
|
fprintf(cgiOut, "Default contents go here. \n");
|
|
fprintf(cgiOut, "</textarea>\n");
|
|
fprintf(cgiOut, "<p>\n");
|
|
fprintf(cgiOut, "Checkbox\n");
|
|
fprintf(cgiOut, "<p>\n");
|
|
fprintf(cgiOut, "<input type=\"checkbox\" name=\"hungry\" checked>Hungry\n");
|
|
fprintf(cgiOut, "<p>\n");
|
|
fprintf(cgiOut, "Text Field containing a Numeric Value\n");
|
|
fprintf(cgiOut, "<p>\n");
|
|
fprintf(cgiOut, "<input type=\"text\" name=\"temperature\" value=\"98.6\">\n");
|
|
fprintf(cgiOut, "Blood Temperature (80.0-120.0)\n");
|
|
fprintf(cgiOut, "<p>\n");
|
|
fprintf(cgiOut, "Text Field containing an Integer Value\n");
|
|
fprintf(cgiOut, "<p>\n");
|
|
fprintf(cgiOut, "<input type=\"text\" name=\"frogs\" value=\"1\">\n");
|
|
fprintf(cgiOut, "Frogs Eaten\n");
|
|
fprintf(cgiOut, "<p>\n");
|
|
fprintf(cgiOut, "Single-SELECT\n");
|
|
fprintf(cgiOut, "<br>\n");
|
|
fprintf(cgiOut, "<select name=\"colors\">\n");
|
|
fprintf(cgiOut, "<option value=\"Red\">Red\n");
|
|
fprintf(cgiOut, "<option value=\"Green\">Green\n");
|
|
fprintf(cgiOut, "<option value=\"Blue\">Blue\n");
|
|
fprintf(cgiOut, "</select>\n");
|
|
fprintf(cgiOut, "<br>\n");
|
|
fprintf(cgiOut, "Multiple-SELECT\n");
|
|
fprintf(cgiOut, "<br>\n");
|
|
fprintf(cgiOut, "<select name=\"flavors\" multiple>\n");
|
|
fprintf(cgiOut, "<option value=\"pistachio\">Pistachio\n");
|
|
fprintf(cgiOut, "<option value=\"walnut\">Walnut\n");
|
|
fprintf(cgiOut, "<option value=\"creme\">Creme\n");
|
|
fprintf(cgiOut, "</select>\n");
|
|
fprintf(cgiOut, "<p>Exclusive Radio Button Group: Age of "
|
|
"Truck in Years\n");
|
|
fprintf(cgiOut, "<input type=\"radio\" name=\"age\" "
|
|
"value=\"1\">1\n");
|
|
fprintf(cgiOut, "<input type=\"radio\" name=\"age\" "
|
|
"value=\"2\">2\n");
|
|
fprintf(cgiOut, "<input type=\"radio\" name=\"age\" "
|
|
"value=\"3\" checked>3\n");
|
|
fprintf(cgiOut, "<input type=\"radio\" name=\"age\" "
|
|
"value=\"4\">4\n");
|
|
fprintf(cgiOut, "<p>Nonexclusive Checkbox Group: "
|
|
"Voting for Zero through Four Candidates\n");
|
|
fprintf(cgiOut, "<input type=\"checkbox\" name=\"vote\" "
|
|
"value=\"A\">A\n");
|
|
fprintf(cgiOut, "<input type=\"checkbox\" name=\"vote\" "
|
|
"value=\"B\">B\n");
|
|
fprintf(cgiOut, "<input type=\"checkbox\" name=\"vote\" "
|
|
"value=\"C\">C\n");
|
|
fprintf(cgiOut, "<input type=\"checkbox\" name=\"vote\" "
|
|
"value=\"D\">D\n");
|
|
fprintf(cgiOut, "<p>File Upload:\n");
|
|
fprintf(cgiOut, "<input type=\"file\" name=\"file\" "
|
|
"value=\"\"> (Select A Local File)\n");
|
|
fprintf(cgiOut, "<p>\n");
|
|
fprintf(cgiOut, "<p>Set a Cookie<p>\n");
|
|
fprintf(cgiOut, "<input name=\"cname\" "
|
|
"value=\"\"> Cookie Name\n");
|
|
fprintf(cgiOut, "<input name=\"cvalue\" "
|
|
"value=\"\"> Cookie Value<p>\n");
|
|
fprintf(cgiOut, "<input type=\"submit\" "
|
|
"name=\"testcgic\" value=\"Submit Request\">\n");
|
|
fprintf(cgiOut, "<input type=\"reset\" "
|
|
"value=\"Reset Request\">\n");
|
|
fprintf(cgiOut, "<p>Save the CGI Environment<p>\n");
|
|
fprintf(cgiOut, "Pressing this button will submit the form, then "
|
|
"save the CGI environment so that it can be replayed later "
|
|
"by calling cgiReadEnvironment (in a debugger, for "
|
|
"instance).<p>\n");
|
|
fprintf(cgiOut, "<input type=\"submit\" name=\"saveenvironment\" "
|
|
"value=\"Save Environment\">\n");
|
|
fprintf(cgiOut, "</form>\n");
|
|
}
|
|
</pre>
|
|
Note the use of <code>enctype="multipart/form-data"</code> in the
|
|
<code>FORM</code> tag. This is absolutely required if the form
|
|
will contain file upload fields, as in the above example. Most
|
|
browsers will not even attempt file uploads without the
|
|
presence of this attribute.
|
|
<h4>Examining CGI environment variables</h4>
|
|
The CGI standard specifies a number of environment variables
|
|
which are set by the server. However, servers are somewhat
|
|
unpredictable as to whether these variables will be null or
|
|
point to empty strings when an environment variable is not set.
|
|
Also, in order to allow the programmer to restore saved
|
|
CGI environments, the cgic library needs have a way of insulating
|
|
the programmer from the actual environment variables.
|
|
<p>
|
|
Instead of calling getenv() to determine the value of a
|
|
variable such as HTTP_USER_AGENT (the browser software being used),
|
|
always use the
|
|
<a href="#variables">cgic copies of the environment variables</a>,
|
|
which are always valid C strings (they are never null, although
|
|
they may point to an empty string). For instance, the cgic
|
|
variable containing the name of the browser software is
|
|
<a href="#cgiUserAgent">cgiUserAgent</a>. The referring URL appears
|
|
in the variable <a href="#cgiReferrer">cgiReferrer</a>.
|
|
<h3><a name="images">How can I generate images from my cgic application?</a></h3>
|
|
cgic can be used in conjunction with the <a href="https://libgd.github.io/">gd graphics library</a>, which
|
|
can produce GIF images on the fly.
|
|
<p>
|
|
The following short sample program hints at the possibilities:
|
|
<pre>
|
|
#include "cgic.h"
|
|
#include "gd.h"
|
|
|
|
char *colors[] = {
|
|
"red", "green", "blue"
|
|
};
|
|
|
|
#define colorsTotal 3
|
|
|
|
int cgiMain() {
|
|
int colorChosen;
|
|
gdImagePtr im;
|
|
int r, g, b;
|
|
/* Use gd to create an image */
|
|
im = gdImageCreate(64, 64);
|
|
r = gdImageColorAllocate(im, 255, 0, 0);
|
|
g = gdImageColorAllocate(im, 0, 255, 0);
|
|
b = gdImageColorAllocate(im, 0, 0, 255);
|
|
/* Now use cgic to find out what color the user requested */
|
|
<a href="#cgiFormSelectSingle">cgiFormSelectSingle</a>("color", 3, &colorChosen, 0);
|
|
/* Now fill with the desired color */
|
|
switch(colorChosen) {
|
|
case 0:
|
|
gdImageFill(im, 32, 32, r);
|
|
break;
|
|
case 1:
|
|
gdImageFill(im, 32, 32, g);
|
|
break;
|
|
case 2:
|
|
gdImageFill(im, 32, 32, b);
|
|
break;
|
|
}
|
|
/* Now output the image. Note the content type! */
|
|
cgiHeaderContentType("image/gif");
|
|
/* Send the image to cgiOut */
|
|
gdImageGif(im, cgiOut);
|
|
/* Free the gd image */
|
|
gdImageDestroy(im);
|
|
return 0;
|
|
}
|
|
</pre>
|
|
Note that this program would need to be linked with both cgic.o
|
|
and libgd.a. Often programs of this type respond to one
|
|
cgiPathInfo value or set of form fields by returning an HTML page
|
|
with an inline image reference that, in turn, generates a GIF image.
|
|
<h3><a name="debug">Debugging CGI applications: using capture</a></h3>
|
|
Debugging CGI applications can be a painful task. Since CGI applications
|
|
run in a special environment created by the web server, it is difficult
|
|
to execute them in a debugger. However, the cgic library provides a way
|
|
of capturing "live" CGI environments to a file, and also provides a way
|
|
to reload saved environments.
|
|
<p>
|
|
The provided program 'capture.c' can be used to capture CGI
|
|
environments. Just change the first line of the cgiMain() function
|
|
of capture.c to save the CGI environment to a filename appropriate
|
|
on your system and type 'make capture'. Then place capture in your
|
|
cgi directory and set the form action or other link you want to test
|
|
to point to it. When the form submission or other link takes place,
|
|
capture will write the CGI environment active at that time to
|
|
the filename you specified in the source. The
|
|
<a href="#cgiReadEnvironment">cgiReadEnvironment()</a> function can then
|
|
be invoked on the same filename at the beginning of the cgiMain() function
|
|
of the application you want to test in order to restore the captured
|
|
environment. You can then execute your program in the debugger of your choice,
|
|
and it should perform exactly as it would have performed had
|
|
it been launched by the actual web server, including file uploads,
|
|
cookies and all other phenomena within the purview of cgic.
|
|
<p>
|
|
<strong>Important:</strong> Make sure you specify the full path, as the
|
|
current working directory of a CGI script may not be what you
|
|
think it is!
|
|
<p>
|
|
<strong>Even More Important:</strong> If you call getenv() yourself
|
|
in your code, instead of using the provided <a href="#variables">
|
|
cgic copies of the CGI environment variables</a>, you will
|
|
<em>not</em> get the values you expect when running with
|
|
a saved CGI environment. Always use the cgic variables instead
|
|
of calling getenv().
|
|
<h3><a name="functions">cgic function reference</a></h3>
|
|
<dl>
|
|
<br><dt><strong><a name="cgiFormString">cgiFormResultType cgiFormString(
|
|
char *name, char *result, int max)</a>
|
|
</strong><br><dd>cgiFormString attempts to retrieve the string sent for the
|
|
specified input field. The text will be copied into
|
|
the buffer specified by result, up to but not
|
|
exceeding max-1 bytes; a terminating null is then
|
|
added to complete the string. Regardless of the newline
|
|
format submitted by the browser, cgiFormString always
|
|
encodes each newline as a single line feed (ascii decimal 10); as
|
|
a result the final string may be slightly shorter than indicated
|
|
by a call to <a href="#cgiFormStringSpaceNeeded">
|
|
cgiFormStringSpaceNeeded</a> but will never be longer.
|
|
cgiFormString returns <a href="#cgiFormSuccess">cgiFormSuccess</a> if the string was
|
|
successfully retrieved,
|
|
<a href="#cgiFormTruncated">cgiFormTruncated</a> if the string was
|
|
retrieved but was truncated to fit the buffer,
|
|
cgiFormEmpty if the string was
|
|
retrieved but was empty, and <a href="#cgiFormNotFound">cgiFormNotFound</a> if no
|
|
such input field was submitted. In the last case,
|
|
an empty string is copied to result.
|
|
<br><br><dt><strong><a name="cgiFormStringNoNewlines">
|
|
cgiFormResultType cgiFormStringNoNewlines(
|
|
char *name, char *result, int max)</a>
|
|
</strong><br><dd>
|
|
cgiFormStringNoNewlines() is exactly equivalent to <a href="#cgiFormString">
|
|
cgiFormString()</a>, except
|
|
that any carriage returns or line feeds that occur in the input
|
|
will be stripped out. The use of this function is recommended
|
|
for single-line text input fields, as some browsers will submit
|
|
carriage returns and line feeds when they should not.
|
|
<br><br><dt><strong><a name="cgiFormStringSpaceNeeded">
|
|
cgiFormResultType cgiFormStringSpaceNeeded(
|
|
char *name, int *length)</a>
|
|
</strong><br><dd>
|
|
cgiFormStringSpaceNeeded() is used to determine the length of the input text
|
|
buffer needed to receive the contents of the specified input field.
|
|
This is useful if the programmer wishes to allocate sufficient memory
|
|
for input of arbitrary length. The actual length of the string
|
|
retrieved by a subsequent call to cgiFormString() may be slightly shorter
|
|
but will never be longer than *result. On success, cgiFormStringSpaceNeeded()
|
|
sets the value pointed to by length to the number of bytes of data,
|
|
including the terminating null, and returns <a href="#cgiFormSuccess">cgiFormSuccess</a>. If no
|
|
value was submitted for the specified field, cgiFormStringSpaceNeeded sets
|
|
the value pointed to by length to 1 and returns <a href="#cgiFormNotFound">cgiFormNotFound</a>. 1 is
|
|
set to ensure space for an empty string (a single null
|
|
character) if cgiFormString is called despite the return value.
|
|
|
|
<br><br><dt><strong><a name="cgiFormStringMultiple">cgiFormResultType cgiFormStringMultiple(
|
|
char *name, char ***ptrToStringArray)</a>
|
|
</strong><br><dd>cgiFormStringMultiple is useful in the unusual case in which several
|
|
input elements in the form have the same name and, for whatever
|
|
reason, the programmer does not wish to use the checkbox, radio
|
|
button and selection menu functions provided below. This is
|
|
occasionally needed if the programmer cannot know
|
|
in advance what values might appear in a multiple-selection list
|
|
or group of checkboxes on a form. The value pointed to
|
|
by result will be set to a pointer to an array of strings; the last
|
|
entry in the array will be a null pointer. This array is allocated
|
|
by the CGI library. Important: when done working with the array,
|
|
you must call cgiStringArrayFree() with the array pointer as the
|
|
argument. cgiFormStringMultiple() returns <a href="#cgiFormSuccess">cgiFormSuccess</a> if at least
|
|
one occurrence of the name is found, <a href="#cgiFormNotFound">cgiFormNotFound</a>
|
|
if no occurrences are found, or cgiFormMemory if not enough
|
|
memory is available to allocate the array to be returned.
|
|
In all cases except the last, ptrToStringArray is set to point to a
|
|
valid array of strings, with the last element in the array being a
|
|
null pointer; in the out-of-memory case ptrToStringArray is set to
|
|
a null pointer.
|
|
|
|
<br><br><dt><strong><a name="cgiFormEntries">cgiFormResultType cgiFormEntries(
|
|
char ***ptrToStringArray)</a>
|
|
</strong><br><dd>cgiFormEntries is useful when the programmer cannot know the names
|
|
of all relevant form fields in advance. The value pointed to
|
|
by result will be set to a pointer to an array of strings; the last
|
|
entry in the array will be a null pointer. This array is allocated
|
|
by the CGI library. Important: when done working with the array,
|
|
you must call cgiStringArrayFree() with the array pointer as the
|
|
argument. cgiFormEntries() returns <a href="#cgiFormSuccess">cgiFormSuccess</a> except in the event of an out of memory error.
|
|
On success, ptrToStringArray is set to point to a
|
|
valid array of strings, with the last element in the array being a
|
|
null pointer; in the out-of-memory case ptrToStringArray is set to
|
|
a null pointer, and
|
|
<a href="#cgiFormOutOfMemory">cgiFormOutOfMemory</a> is returned.
|
|
|
|
<br><br><dt><strong><a name="cgiStringArrayFree">void cgiStringArrayFree(char **stringArray)
|
|
</a>
|
|
</strong><br><dd>
|
|
cgiStringArrayFree() is used to free the memory associated with
|
|
a string array created by
|
|
<a href="#cgiFormStringMultiple">cgiFormStringMultiple()</a>,
|
|
<a href="#cgiFormEntries">cgiFormEntries()</a>, or
|
|
<a href="#cgiFormCookies">cgiFormCookies()</a>.
|
|
<br><br><dt><strong><a name="cgiFormInteger">cgiFormResultType cgiFormInteger(
|
|
char *name, int *result, int defaultV)</a>
|
|
</strong><br><dd>cgiFormInteger() attempts to retrieve the integer sent for the
|
|
specified input field. The value pointed to by result
|
|
will be set to the value submitted. cgiFormInteger() returns
|
|
cgiFormSuccess if the value was successfully retrieved,
|
|
cgiFormEmpty if the value submitted is an empty string,
|
|
cgiFormBadType if the value submitted is not an integer,
|
|
and <a href="#cgiFormNotFound">cgiFormNotFound</a> if no such input field was submitted.
|
|
In the last three cases, the value pointed to by result
|
|
is set to the specified default.
|
|
<br><br><dt><strong><a name="cgiFormIntegerBounded">
|
|
cgiFormResultType cgiFormIntegerBounded(
|
|
char *name, int *result, int min, int max, int defaultV)</a>
|
|
</strong><br><dd>cgiFormIntegerBounded() attempts to retrieve the integer sent for the
|
|
specified input field, and constrains the result to be within
|
|
the specified bounds. The value pointed to by result
|
|
will be set to the value submitted. cgiFormIntegerBounded() returns
|
|
cgiFormSuccess if the value was successfully retrieved,
|
|
<a href="#cgiFormConstrained">cgiFormConstrained</a> if the value was out of bounds and result
|
|
was adjusted accordingly, <a href="#cgiFormEmpty">cgiFormEmpty</a> if the value submitted is
|
|
an empty string, <a href="#cgiFormBadType">cgiFormBadType</a> if the value submitted is not an
|
|
integer, and <a href="#cgiFormNotFound">cgiFormNotFound</a> if no such input field was submitted.
|
|
In the last three cases, the value pointed to by result
|
|
is set to the specified default.
|
|
|
|
<br><br><dt><strong><a name="cgiFormDouble">cgiFormResultType cgiFormDouble(
|
|
char *name, double *result, double defaultV)</a>
|
|
</strong><br><dd>cgiFormDouble attempts to retrieve the floating-point value sent for
|
|
the specified input field. The value pointed to by result
|
|
will be set to the value submitted. cgiFormDouble returns
|
|
cgiFormSuccess if the value was successfully retrieved,
|
|
cgiFormEmpty if the value submitted is an empty string,
|
|
cgiFormBadType if the value submitted is not a number,
|
|
and <a href="#cgiFormNotFound">cgiFormNotFound</a> if no such input field was submitted.
|
|
In the last three cases, the value pointed to by result
|
|
is set to the specified default.
|
|
<br><br><dt><strong><a name="cgiFormDoubleBounded">
|
|
cgiFormResultType cgiFormDoubleBounded(
|
|
char *name, double *result, double min, double max,
|
|
double defaultV)</a>
|
|
</strong><br><dd>
|
|
cgiFormDoubleBounded() attempts to retrieve the floating-point
|
|
value sent for the specified input field, and constrains the
|
|
result to be within the specified bounds. The value pointed to by
|
|
result will be set to the value submitted. cgiFormDoubleBounded() returns
|
|
cgiFormSuccess if the value was successfully retrieved,
|
|
<a href="#cgiFormConstrained">cgiFormConstrained</a> if the value was out of bounds and result
|
|
was adjusted accordingly, <a href="#cgiFormEmpty">cgiFormEmpty</a> if the value submitted is
|
|
an empty string, <a href="#cgiFormBadType">cgiFormBadType</a> if the value submitted is not a
|
|
number, and <a href="#cgiFormNotFound">cgiFormNotFound</a> if no such input field was submitted.
|
|
In the last three cases, the value pointed to by result
|
|
is set to the specified default.
|
|
|
|
<br><br><dt><strong><a name="cgiFormSelectSingle">
|
|
cgiFormResultType cgiFormSelectSingle(
|
|
char *name, char **choicesText, int choicesTotal,
|
|
int *result, int defaultV)</a>
|
|
</strong><br><dd>
|
|
cgiFormSelectSingle() retrieves the selection number associated with a
|
|
<SELECT> element that does not allow multiple selections. name
|
|
should identify the NAME attribute of the <SELECT> element. choicesText
|
|
should point to an array of strings identifying each choice;
|
|
choicesTotal should indicate the total number of choices. The value
|
|
pointed to by result will be set to the position of the actual choice
|
|
selected within the choicesText array, if any, or to the value of
|
|
default, if no selection was submitted or an invalid selection was
|
|
made. cgiFormSelectSingle() returns <a href="#cgiFormSuccess">cgiFormSuccess</a> if the value was
|
|
successfully retrieved, <a href="#cgiFormNotFound">cgiFormNotFound</a> if no selection
|
|
was submitted, and <a href="#cgiFormNoSuchChoice">cgiFormNoSuchChoice</a> if the selection
|
|
does not match any of the possibilities in the choicesText array.
|
|
<br><dt><strong>
|
|
<a name="cgiFormSelectMultiple">
|
|
cgiFormResultType cgiFormSelectMultiple(
|
|
char *name, char **choicesText, int choicesTotal,
|
|
int *result, int *invalid)</a>
|
|
</strong><br><dd>cgiFormSelectMultiple() retrieves the selection numbers associated with a
|
|
<SELECT> element that does allow multiple selections. name should
|
|
identify the NAME attribute of the <SELECT> element. choicesText
|
|
should point to an array of strings identifying each choice;
|
|
choicesTotal should indicate the total number of choices. result
|
|
should point to an array of integers with as many elements as there
|
|
are strings in the choicesText array. For each choice in the
|
|
choicesText array that is selected, the corresponding integer in
|
|
the result array will be set to one; other entries in the result
|
|
array will be set to zero. cgiFormSelectMultiple() returns <a href="#cgiFormSuccess">cgiFormSuccess</a>
|
|
if at least one valid selection was successfully retrieved or
|
|
cgiFormNotFound if no valid selections were submitted.
|
|
The integer pointed to by invalid is set to the number of
|
|
invalid selections that were submitted, which should be zero
|
|
unless the form and the choicesText array do not agree.
|
|
|
|
<br><br><dt><strong>
|
|
<a name="cgiFormSubmitClicked">
|
|
cgiFormResultType cgiFormSubmitClicked(
|
|
char *name)</a>
|
|
</strong><br><dd>
|
|
It is often desirable to know whether a particular submit button was clicked,
|
|
when multiple submit buttons with different name attributes exist.
|
|
cgiFormSubmitClicked is an alternative name for the
|
|
<a href="#cgiFormCheckboxSingle">cgiFormCheckboxSingle</a> function,
|
|
which is suitable for testing whether a particular submit button
|
|
was used.
|
|
<br><br><dt><strong>
|
|
<a name="cgiFormCheckboxSingle">
|
|
cgiFormResultType cgiFormCheckboxSingle(
|
|
char *name)</a>
|
|
</strong><br><dd>
|
|
cgiFormCheckboxSingle determines whether the checkbox with the specified name
|
|
is checked. cgiFormCheckboxSingle returns <a href="#cgiFormSuccess">cgiFormSuccess</a> if the
|
|
button is checked, <a href="#cgiFormNotFound">cgiFormNotFound</a> if the checkbox is
|
|
not checked. cgiFormCheckboxSingle is intended for single
|
|
checkboxes with a unique name; see below for functions to
|
|
deal with multiple checkboxes with the same name, and
|
|
with radio buttons.
|
|
|
|
<br><br><dt><strong><a name="cgiFormCheckboxMultiple">
|
|
cgiFormResultType cgiFormCheckboxMultiple(
|
|
char *name, char **valuesText, int valuesTotal,
|
|
int *result, int *invalid)</a>
|
|
</strong><br><dd>cgiFormCheckboxMultiple() determines which checkboxes among a group
|
|
of checkboxes with the same name are checked. This is distinct
|
|
from radio buttons (see <a href="#cgiFormRadio">cgiFormRadio</a>).
|
|
valuesText
|
|
should point to an array of strings identifying the VALUE
|
|
attribute of each checkbox; valuesTotal should indicate the total
|
|
number of checkboxes. result should point to an array of integers with
|
|
as many elements as there are strings in the valuesText array. For
|
|
each choice in the valuesText array that is selected, the corresponding
|
|
integer in the result array will be set to one; other entries in the
|
|
result array will be set to zero. cgiFormCheckboxMultiple returns
|
|
cgiFormSuccess if at least one valid checkbox was checked or
|
|
cgiFormNotFound if no valid checkboxes were checked.
|
|
The integer pointed to by invalid is set to the number of
|
|
invalid selections that were submitted, which should be zero
|
|
unless the form and the valuesText array do not agree.
|
|
<br><br><dt><strong><a name="cgiFormRadio">
|
|
cgiFormResultType cgiFormRadio(
|
|
char *name, char **valuesText, int valuesTotal,
|
|
int *result, int defaultV)</a>
|
|
</strong><br><dd>cgiFormRadio() determines which, if any, of a group of radio boxes with
|
|
the same name was selected. valuesText should point to an array of
|
|
strings identifying the VALUE attribute of each radio box;
|
|
valuesTotal should indicate the total number of radio boxes. The value
|
|
pointed to by result will be set to the position of the actual choice
|
|
selected within the valuesText array, if any, or to the value of
|
|
default, if no radio box was checked or an invalid selection was
|
|
made. cgiFormRadio() returns <a href="#cgiFormSuccess">cgiFormSuccess</a> if a checked radio box was
|
|
found in the group, <a href="#cgiFormNotFound">cgiFormNotFound</a> if no box was checked, and
|
|
<a href="#cgiFormNoSuchChoice">cgiFormNoSuchChoice</a> if the radio box submitted does not match any of
|
|
the possibilities in the valuesText array.
|
|
|
|
<br><dt><strong><a name="cgiFormFileName">cgiFormResultType cgiFormFileName(
|
|
char *name, char *fileName, int max)</a>
|
|
</strong><br><dd>cgiFormFileName attempts to retrieve the file name uploaded by the
|
|
user for the specified form input field of type <code>file</code>.
|
|
<strong>NEVER, EVER TRUST THIS FILENAME TO BE REASONABLE AND
|
|
SAFE FOR DIRECT USE ON THE SERVER SIDE.</strong>
|
|
The text will be copied into
|
|
the buffer specified by fileName, up to but not
|
|
exceeding max-1 bytes; a terminating null is then
|
|
added to complete the string. cgiFormFileName returns
|
|
<a href="#cgiFormSuccess">cgiFormSuccess</a> if the string was
|
|
successfully retrieved and was not empty,
|
|
<a href="#cgiFormNoFileName">cgiFormNoFileName</a> if the string was
|
|
successfully retrieved but empty indicating that no file was uploaded,
|
|
<a href="#cgiFormTruncated">cgiFormTruncated</a> if the string was
|
|
retrieved but was truncated to fit the buffer,
|
|
and <a href="#cgiFormNotFound">cgiFormNotFound</a> if no
|
|
such input field was submitted. In the last case,
|
|
an empty string is copied to result.
|
|
<br><dt><strong><a name="cgiFormFileSize">cgiFormResultType cgiFormFileSize(
|
|
char *name, int *sizeP)</a>
|
|
</strong><br><dd>cgiFormFileSize attempts to retrieve the size, in bytes, of a
|
|
file uploaded by the browser in response to the
|
|
input field of type <code>file</code> specified by the
|
|
<code>name</code> parameter. On success, the size is stored
|
|
to *sizeP, and this function returns
|
|
<a href="#cgiFormSuccess">cgiFormSuccess</a>. If the form
|
|
field does not exist, this function returns
|
|
<a href="#cgiFormNotFound">cgiFormNotFound</a>.
|
|
If the form field exists but no file was uploaded, this function
|
|
returns <a href="#cgiFormNotAFile">cgiFormNotAFile</a>.
|
|
<br><dt><strong><a name="cgiFormFileContentType">cgiFormResultType cgiFormFileContentType(
|
|
char *name, char *contentType, int max)</a>
|
|
</strong><br><dd>cgiFormString attempts to retrieve the content name claimed by the
|
|
user for the specified form input field of type <code>file</code>.
|
|
<strong>THERE IS NO GUARANTEE THAT THE CONTENT TYPE WILL BE
|
|
ACCURATE.</strong>
|
|
The content type string will be copied into
|
|
the buffer specified by contentType, up to but not
|
|
exceeding max-1 bytes; a terminating null is then
|
|
added to complete the string. cgiFormFileContentType returns
|
|
<a href="#cgiFormSuccess">cgiFormSuccess</a> if the string was
|
|
successfully retrieved and was not empty,
|
|
<a href="#cgiFormNoContentType">cgiFormNoContentType</a> if the string was
|
|
successfully retrieved but empty indicating that no file was uploaded
|
|
or the browser did not know the content type,
|
|
<a href="#cgiFormTruncated">cgiFormTruncated</a> if the string was
|
|
retrieved but was truncated to fit the buffer,
|
|
and <a href="#cgiFormNotFound">cgiFormNotFound</a> if no
|
|
such input field was submitted. In the last case,
|
|
an empty string is copied to result.
|
|
|
|
<br><dt><strong><a name="cgiFormFileOpen">cgiFormResultType cgiFormFileOpen(
|
|
char *name, cgiFilePtr *cfpp)</a>
|
|
</strong><br><dd>cgiFormFileOpen attempts to open the actual uploaded file data for
|
|
the specified form field of type <code>file</code>. Upon success,
|
|
this function returns retrieve the content name claimed by the
|
|
user for the specified form input field of type <code>file</code>.
|
|
On success, this function sets *cfpp to a valid cgiFilePtr
|
|
object for use with <a href="#cgiFormFileRead">cgiFormFileRead</a>
|
|
and returns <a href="#cgiFormSuccess">cgiFormSuccess</a>.
|
|
On failure, this function sets *cfpp to a null pointer, and
|
|
returns <a href="#cgiFormNotFound">cgiFormNotFound</a>,
|
|
<a href="#cgiFormNotAFile">cgiFormNotAFile</a>,
|
|
<a href="#cgiFormMemory">cgiFormMemory</a> or
|
|
<a href="#cgiFormIO">cgiFormIO</a> as appropriate.
|
|
<p>
|
|
See also <a href="#cgiFormFileRead">cgiFormFileRead</a>
|
|
and <a href="#cgiFormFileClose">cgiFormFileClose</a>.
|
|
<br><dt><strong><a name="cgiFormFileRead">cgiFormResultType cgiFormFileRead(
|
|
cgiFilePtr cfp, char *buffer, int bufferSize, int *gotP)</a>
|
|
</strong><br><dd>cgiFormFileRead attempts to read up to <code>bufferSize</code>
|
|
bytes from a cgiFilePtr object previously opened with
|
|
<a href="#cgiFormFileOpen">cgiFormFileOpen</a>. If any data
|
|
is successfully read, it is copied to <code>buffer</code>,
|
|
and the number of bytes successfully read is stored
|
|
to <code>*gotP</code>. This function returns
|
|
<a href="#cgiFormSuccess">cgiFormSuccess</a> if any data
|
|
is successfully read. At end of file, this function
|
|
returns <a href="#cgiFormEOF">cgiFormEOF</a>. In the event
|
|
of an I/O error, this function returns
|
|
<a href="#cgiFormIO">cgiFormIO</a>. If cfp is a null pointer,
|
|
this function returns <a href="#cgiFormOpenFailed">cgiFormOpenFailed</a>.
|
|
<p>
|
|
See also <a href="#cgiFormFileOpen">cgiFormFileOpen</a>
|
|
and <a href="#cgiFormFileClose">cgiFormFileClose</a>.
|
|
<br><dt><strong><a name="cgiFormFileClose">cgiFormResultType cgiFormFileClose(
|
|
cgiFilePtr cfp)</a>
|
|
</strong><br><dd>cgiFormFileClose closes a cgiFilePtr object previously opened
|
|
with <a href="#cgiFormFileOpen">cgiFormFileOpen</a>, freeing
|
|
memory and other system resources. This
|
|
function returns <a href="#cgiFormSuccess">cgiFormSuccess</a>
|
|
unless cfp is null, in which case
|
|
<a href="#cgiFormOpenFailed">cgiFormOpenFailed</a> is returned.
|
|
<p>
|
|
See also <a href="#cgiFormFileOpen">cgiFormFileOpen</a>
|
|
and <a href="#cgiFormFileRead">cgiFormFileRead</a>.
|
|
<br><br><dt><strong><a name="cgiHeaderLocation">
|
|
void cgiHeaderLocation(char *redirectUrl)</a>
|
|
</strong><br><dd>
|
|
cgiHeaderLocation() should be called if the programmer wishes to
|
|
redirect the user to a different URL. No futher output
|
|
is needed in this case.
|
|
<p>
|
|
If you wish to set cookies,
|
|
<strong>you must make your calls to
|
|
<a href="#cgiHeaderCookieSet">cgiHeaderCookieSet</a>
|
|
and
|
|
<a href="#cgiHeaderCookieSetInteger">cgiHeaderCookieSetInteger</a>
|
|
</strong> BEFORE invoking cgiHeaderLocation.
|
|
<br><br><dt><strong><a name="cgiHeaderStatus">
|
|
void cgiHeaderStatus(int status, char *statusMessage)</a>
|
|
</strong><br><dd>
|
|
cgiHeaderStatus() should be called if the programmer wishes to
|
|
output an HTTP error status code instead of a document. The status
|
|
code is the first argument; the second argument is the status
|
|
message to be displayed to the user.
|
|
<p>
|
|
If you wish to set cookies,
|
|
<strong>you must make your calls to
|
|
<a href="#cgiHeaderCookieSet">cgiHeaderCookieSet</a>
|
|
and
|
|
<a href="#cgiHeaderCookieSetInteger">cgiHeaderCookieSetInteger</a>
|
|
</strong> BEFORE invoking cgiHeaderStatus.
|
|
<br><br><dt><strong><a name="cgiHeaderContentType">
|
|
void cgiHeaderContentType(char *mimeType)</a>
|
|
</strong><br><dd>
|
|
cgiHeaderContentType() should be called if the programmer wishes to
|
|
output a new document in response to the user's request. This is
|
|
the normal case. The single argument is the MIME document type
|
|
of the response; typical values are "text/html" for HTML documents,
|
|
"text/plain" for plain ASCII without HTML tags, "image/gif" for
|
|
a GIF image and "audio/basic" for .au-format audio.
|
|
<p>
|
|
If you wish to set cookies,
|
|
<strong>you must make your calls to
|
|
<a href="#cgiHeaderCookieSet">cgiHeaderCookieSet</a>
|
|
and
|
|
<a href="#cgiHeaderCookieSetInteger">cgiHeaderCookieSetInteger</a>
|
|
</strong> BEFORE invoking cgiHeaderContentType.
|
|
<br><br><dt><strong><a name="cgiHeaderCookieSet">
|
|
void cgiHeaderCookieSet(char *name, char *value,
|
|
int secondsToLive, char *path, char *domain, int options)</a>
|
|
</strong><br><dd>
|
|
cgiHeaderCookieSet() should be called when the programmer wishes
|
|
to store a piece of information in the user's browser, so that the
|
|
stored information is again presented to the server on subsequent
|
|
accesses to the relevant site. The first argument is the name of the
|
|
cookie to be stored; for best results in all browsers, use a short
|
|
name without spaces or unusual punctuation. The second argument is
|
|
the value of the cookie to be stored. Again, for best results, use
|
|
a short string; it is recommended that cookies be used to store a
|
|
unique identifier which is then used to look up more detailed
|
|
information in a database on the server side. Attempts to store
|
|
elaborate information on the browser side are much more likely to fail.
|
|
The third argument is the number of seconds that the cookie should
|
|
be kept by the browser; 86400 is a single full day, 365*86400 is
|
|
roughly one year. The fourth argument is the partial URL of the
|
|
web site within which the cookie is relevant. If the cookie should
|
|
be sent to the server for every access to the entire site,
|
|
set this argument to <code>/</code>. The final argument is the
|
|
web site name or entire domain for which this cookie should be
|
|
submitted; if you choose to have the cookie sent back for an
|
|
entire domain, this argument must begin with a dot, such as
|
|
<code>.boutell.dev</code>. The cgic variables <a name="#cgiScriptName">cgiScriptName</a>
|
|
and <a name="#cgiServerName">cgiServerName</a> are convenient
|
|
values for the fourth and fifth arguments.
|
|
The sixth argument is a bitmask for specifying cookie security options.
|
|
It can be zero (no options) or a bitwise-OR of the following
|
|
<code>enum cgiCookieOption</code> values:
|
|
<ul>
|
|
<li><code>cgiCookieSecure</code></li>
|
|
<li><code>cgiCookieHttpOnly</code></li>
|
|
<li><code>cgiCookieSameSiteStrict</code></li>
|
|
</ul>
|
|
See <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Cookies">HTTP cookies</a>
|
|
for more information.<br>
|
|
See also <a href="#cgiHeaderCookieSetString">cgiHeaderCookieSetString</a>,
|
|
<a href="#cgiHeaderCookieSetInteger">cgiHeaderCookieSetInteger</a>,
|
|
<a href="#cgiCookieString">cgiCookieString</a>,
|
|
<a href="#cgiCookieInteger">cgiCookieInteger</a> and
|
|
<a href="#cgiCookies">cgiCookies</a>.
|
|
<br><br><dt><strong><a name="cgiHeaderCookieSetString">
|
|
void cgiHeaderCookieSetString(char *name, char *value,
|
|
int secondsToLive, char *path, char *domain)</a>
|
|
</strong><br><dd>
|
|
cgiHeaderCookieSetString() is kept for API compability reasons. It calls
|
|
<a href"#cgiHeaderCookieSet()">cgiHeaderCookieSet</a> with zero as sixth
|
|
argument, i.e. no cookie options are set.
|
|
<br><br><dt><strong><a name="cgiHeaderCookieSetInteger">
|
|
void cgiHeaderCookieSetInteger(char *name, int value,
|
|
int secondsToLive, char *path, char *domain)</a>
|
|
</strong><br><dd>
|
|
cgiHeaderCookieSetInteger() is identical to
|
|
<a href="#cgiHeaderCookieSetString">cgiHeaderCookieSetString</a>,
|
|
except that the value to be set is an integer rather than a string.
|
|
See <a href="#cgiHeaderCookieSetString">cgiHeaderCookieSetString</a>
|
|
for complete information.
|
|
<br>
|
|
<br><dt><strong><a name="cgiCookieString">cgiFormResultType cgiCookieString(
|
|
char *name, char *result, int max)</a>
|
|
</strong><br><dd>cgiFormString attempts to retrieve the string sent for the
|
|
specified cookie (browser-side persistent storage). The
|
|
text will be copied into
|
|
the buffer specified by result, up to but not
|
|
exceeding max-1 bytes; a terminating null is then
|
|
added to complete the string.
|
|
cgiCookieString returns <a href="#cgiFormSuccess">cgiFormSuccess</a> if the string was
|
|
successfully retrieved,
|
|
<a href="#cgiFormTruncated">cgiFormTruncated</a> if the string was
|
|
retrieved but was truncated to fit the buffer,
|
|
cgiFormEmpty if the string was
|
|
retrieved but was empty, and <a href="#cgiFormNotFound">cgiFormNotFound</a> if no
|
|
such cookie was submitted. In the last case,
|
|
an empty string is copied to result.
|
|
<br><br><dt><strong><a name="cgiCookieInteger">cgiFormResultType cgiCookieInteger(
|
|
char *name, int *result, int defaultV)</a>
|
|
See also <a href="#cgiCookieString">cgiCookieInteger</a>,
|
|
<a href="#cgiCookies">cgiCookies</a>,
|
|
<a href="#cgiHeaderCookieSet">cgiHeaderCookieSet</a>,
|
|
<a href="#cgiHeaderCookieSetString">cgiHeaderCookieSetString</a>, and
|
|
<a href="#cgiHeaderCookieSetInteger">cgiHeaderCookieSetInteger</a>.
|
|
</strong><br><dd>cgiCookieInteger() attempts to retrieve the integer sent for the
|
|
specified cookie (browser-side persistent storage). The value
|
|
pointed to by result will be set to the value submitted.
|
|
cgiCookieInteger() returns
|
|
cgiFormSuccess if the value was successfully retrieved,
|
|
cgiFormEmpty if the value submitted is an empty string,
|
|
cgiFormBadType if the value submitted is not an integer,
|
|
and <a href="#cgiFormNotFound">cgiFormNotFound</a> if no such
|
|
input field was submitted. In the last three cases, the value
|
|
pointed to by result is set to the specified default.
|
|
See also <a href="#cgiCookieString">cgiCookieString</a>,
|
|
<a href="#cgiCookies">cgiCookies</a>,
|
|
<a href="#cgiHeaderCookieSet">cgiHeaderCookieSet</a>,
|
|
<a href="#cgiHeaderCookieSetString">cgiHeaderCookieSetString</a>, and
|
|
<a href="#cgiHeaderCookieSetInteger">cgiHeaderCookieSetInteger</a>.
|
|
<br><br><dt><strong><a name="cgiCookies">cgiFormResultType cgiCookies(
|
|
char *name, char ***ptrToStringArray)</a>
|
|
</strong><br><dd>cgiCookies is useful when the programmer cannot know the names
|
|
of all relevant cookies (browser-side persistent strings) in advance.
|
|
The value pointed to by result will be set to a pointer to an array
|
|
of strings; the last
|
|
entry in the array will be a null pointer. This array is allocated
|
|
by the CGI library. Important: when done working with the array,
|
|
you must call cgiStringArrayFree() with the array pointer as the
|
|
argument. cgiCookies() returns <a href="#cgiFormSuccess">cgiFormSuccess</a> except in the event of an out of memory error.
|
|
On success, ptrToStringArray is set to point to a
|
|
valid array of strings, with the last element in the array being a
|
|
null pointer; in the out-of-memory case ptrToStringArray is set to
|
|
a null pointer, and
|
|
<a href="#cgiFormOutOfMemory">cgiFormOutOfMemory</a> is returned.
|
|
<br><br><dt><strong><a name="cgiHtmlEscape">
|
|
cgiFormResultType cgiHtmlEscape(char *s)</a>
|
|
</strong><br><dd>
|
|
cgiHtmlEscape() outputs the specified null-terminated string to
|
|
<a href="#cgiOut">cgiOut</a>,
|
|
escaping any <, &, and > characters encountered correctly so that
|
|
they do not interfere with HTML markup. Returns
|
|
<a href="#cgiFormSuccess">cgiFormSuccess</a>, or
|
|
<a href="#cgiFormIO">cgiFormIO</a> in the event of an I/O error.
|
|
<p>
|
|
<br><br><dt><strong><a name="cgiHtmlEscapeData">
|
|
cgiFormResultType cgiHtmlEscapeData(char *data, int len)</a>
|
|
</strong><br><dd>
|
|
cgiHtmlEscapeData() is identical to <a href="#cgiHtmlEscape">cgiHtmlEscape</a>,
|
|
except that the data is not null-terminated. This version of the function
|
|
outputs <code>len</code> bytes. See <a href="#cgiHtmlEscape">cgiHtmlEscape</a>
|
|
for more information.
|
|
<br><br><dt><strong><a name="cgiValueEscape">
|
|
cgiFormResultType cgiValueEscape(char *s)</a>
|
|
</strong><br><dd>
|
|
cgiValueEscape() outputs the specified null-terminated string to
|
|
<a href="#cgiOut">cgiOut</a>,
|
|
escaping any " characters encountered correctly so that
|
|
they do not interfere with the quotation marks of HTML attribute
|
|
values. This is useful when outputting a string as part of the
|
|
value attribute of an input tag, or the href attribute of a link
|
|
or form tag. This function returns
|
|
<a href="#cgiFormSuccess">cgiFormSuccess</a>, or
|
|
<a href="#cgiFormIO">cgiFormIO</a> in the event of an I/O error.
|
|
<p>
|
|
<br><br><dt><strong><a name="cgiValueEscapeData">
|
|
cgiFormResultType cgiValueEscapeData(char *data, int len)</a>
|
|
</strong><br><dd>
|
|
cgiValueEscapeData() is identical to <a href="#cgiValueEscape">cgiValueEscape</a>,
|
|
except that the data is not null-terminated. This version of the function
|
|
outputs <code>len</code> bytes. See <a href="#cgiValueEscape">cgiValueEscape</a>
|
|
for more information.
|
|
<br><br><dt><strong><a name="cgiWriteEnvironment">
|
|
cgiEnvironmentResultType cgiWriteEnvironment(char *filename)</a>
|
|
</strong><br><dd>
|
|
cgiWriteEnvironment() can
|
|
be used to write the entire CGI environment, including
|
|
form data, to the specified output file; <a href="#cgiReadEnvironment">
|
|
cgiReadEnvironment()</a>
|
|
can then be used to restore that environment from the specified
|
|
input file for debugging. Of course, these will only work as expected
|
|
if you use the <a href="#variables">cgic copies of the CGI environment
|
|
variables</a> and <a href="#cgiIn">cgiIn</a> and
|
|
<a href="#cgiOut">cgiOut</a> rather than stdin and
|
|
stdout (also see above). These functions are useful in order
|
|
to capture real CGI situations while the web server is running, then
|
|
recreate them in a debugging environment. Both functions
|
|
return <a href="#cgiEnvironmentSuccess">cgiEnvironmentSuccess</a> on
|
|
success, <a href="#cgiEnvironmentIO">cgiEnvironmentIO</a> on an I/O
|
|
error, and <a href="#cgiEnvironmentMemory">cgiEnvironmentMemory</a>
|
|
on an out-of-memory error.
|
|
<br><br><dt><strong><a name="cgiReadEnvironment">
|
|
cgiEnvironmentResultType cgiReadEnvironment(char *filename)</a>
|
|
</strong><br><dd>
|
|
cgiReadEnvironment() restores a CGI environment saved to the specified file by
|
|
<a href="#cgiWriteEnvironment">cgiWriteEnvironment().</a>
|
|
Of course, these will only work as expected
|
|
if you use the <a href="#variables">cgic copies of the CGI environment
|
|
variables</a> and <a href="#cgiIn">cgiIn</a> and
|
|
<a href="#cgiOut">cgiOut</a> rather than stdin and
|
|
stdout (also see above). These functions are useful in order
|
|
to capture real CGI situations while the web server is running, then
|
|
recreate them in a debugging environment. Both functions
|
|
return <a href="#cgiEnvironmentSuccess">cgiEnvironmentSuccess</a> on success,
|
|
<a href="#cgiEnvironmentIO">cgiEnvironmentIO</a> on an I/O error, and
|
|
<a href="#cgiEnvironmentMemory">cgiEnvironmentMemory</a>
|
|
on an out-of-memory error.
|
|
<br><br><dt><strong><a name="cgiMain">int cgiMain()</a>
|
|
</strong><br><dd><strong>The programmer must write this function</strong>, which performs
|
|
the unique task of the program and is invoked by the true main()
|
|
function, found in the cgic library itself. The return value from
|
|
cgiMain will be the return value of the program. It is expected that
|
|
the user will make numerous calls to the cgiForm functions
|
|
from within this function. See <a href="#howto">how to write
|
|
a cgic application</a> for details.
|
|
</dl>
|
|
<h3><a name="variables">cgic variable reference</a></h3>
|
|
This section provides a reference guide to the various global
|
|
variables provided by cgic for the programmer to utilize.
|
|
These variables should always be used in preference to
|
|
stdin, stdout, and calls to getenv() in order to ensure
|
|
compatibility with the <a href="#debug">cgic CGI debugging features</a>.
|
|
<p>
|
|
Most of these variables are equivalent to various CGI environment
|
|
variables. The most important difference is that the cgic
|
|
environment string variables are never null pointers. They will always
|
|
point to valid C strings of zero or more characters.
|
|
<dl>
|
|
<br><dt><strong><a name="cgiServerSoftware">char *cgiServerSoftware</a>
|
|
</strong><br><dd>Points to the name of the server software,
|
|
or to an empty string if unknown.
|
|
<br><dt><strong><a name="cgiServerName">char *cgiServerName</a>
|
|
</strong><br><dd>Points to the name of the server,
|
|
or to an empty string if unknown.
|
|
<br><dt><strong><a name="cgiGatewayInterface">char *cgiGatewayInterface</a>
|
|
</strong><br><dd>Points to the name of the gateway interface (usually CGI/1.1),
|
|
or to an empty string if unknown.
|
|
<br><dt><strong><a name="cgiServerProtocol">char *cgiServerProtocol</a>
|
|
</strong><br><dd>Points to the protocol in use (usually HTTP/1.0),
|
|
or to an empty string if unknown.
|
|
<br><dt><strong><a name="cgiServerPort">char *cgiServerPort</a>
|
|
</strong><br><dd>Points to the port number on which the server is listening
|
|
for HTTP connections (usually 80), or an empty string if unknown.
|
|
<br><dt><strong><a name="cgiRequestMethod">char *cgiRequestMethod</a>
|
|
</strong><br><dd>Points to the method used in the request (usually GET or POST),
|
|
or an empty string if unknown (this should not happen).
|
|
<br><dt><strong><a name="cgiPathInfo">char *cgiPathInfo</a>
|
|
</strong><br><dd>Most web servers recognize any additional path information in
|
|
the URL of the request beyond the name of the CGI program itself and
|
|
pass that information on to the program. cgiPathInfo points to this
|
|
additional path information.
|
|
<br><dt><strong><a name="cgiPathTranslated">char *cgiPathTranslated</a>
|
|
</strong><br><dd>Most web servers recognize any additional path information in
|
|
the URL of the request beyond the name of the CGI program itself and
|
|
pass that information on to the program. cgiPathTranslated points
|
|
to this additional path information, translated by the server into a
|
|
filesystem path on the local server.
|
|
<br><dt><strong><a name="cgiScriptName">char *cgiScriptName</a>
|
|
</strong><br><dd>Points to the name under which the program was invoked.
|
|
<br><dt><strong><a name="cgiQueryString">char *cgiQueryString</a>
|
|
</strong><br><dd>Contains any query information submitted by the user as a result
|
|
of a GET-method form or an <ISINDEX> tag. Note that this
|
|
information need not be parsed directly unless an <ISINDEX> tag
|
|
was used; normally it is parsed automatically by the cgic library. Use
|
|
the cgiForm family of functions to retrieve the values associated
|
|
with form input fields. See <a href="#howto">how to write
|
|
a cgic application</a> for more information.
|
|
<br><dt><strong><a name="cgiRemoteHost">char *cgiRemoteHost</a>
|
|
</strong><br><dd>Points to the fully resolved hostname of the browser, if known,
|
|
or an empty string if unknown.
|
|
<br><dt><strong><a name="cgiRemoteAddr">char *cgiRemoteAddr</a>
|
|
</strong><br><dd>Points to the dotted-decimal IP address of the browser, if known,
|
|
or an empty string if unknown.
|
|
<br><dt><strong><a name="cgiAuthType">char *cgiAuthType</a>
|
|
</strong><br><dd>Points to the type of authorization used for the request,
|
|
if any, or an empty string if none or unknown.
|
|
<br><dt><strong><a name="cgiRemoteUser">char *cgiRemoteUser</a>
|
|
</strong><br><dd>Points to the user name under which the user has
|
|
authenticated; an empty string if no authentication has
|
|
taken place. The certainty of this information depends on
|
|
the type of authorization in use; see
|
|
<a href="#cgiAuthType">cgiAuthType</a>.
|
|
<br><dt><strong><a name="cgiRemoteIdent">char *cgiRemoteIdent</a>
|
|
</strong><br><dd>Points to the user name volunteered by the user via
|
|
the user identification protocol; an empty
|
|
string if unknown. This information is not secure.
|
|
Identification demons can be installed by users on
|
|
insecure systems such as Windows machines.
|
|
<br><dt><strong><a name="cgiContentType">char *cgiContentType</a>
|
|
</strong><br><dd>Points to the MIME content type of the information
|
|
submitted by the user, if any; an empty string if no
|
|
information was submitted. If this string is equal to
|
|
<code>application/x-www-form-urlencoded</code> or
|
|
<code>multipart/form-data</code>, the cgic
|
|
library will automatically examine the form data submitted.
|
|
If this string has any other non-empty value, a different
|
|
type of data has been submitted. This is currently very rare,
|
|
as most browsers can only submit forms and file uploads which
|
|
cgic parses directly.
|
|
<br><dt><strong><a name="cgiContentType">char *cgiCookie</a>
|
|
</strong><br><dd>Points to the raw cookie (browser-side persistent storage)
|
|
data submitted by the web browser.
|
|
Programmers should use the functions <a href="#cgiCookies">cgiCookies</a>,
|
|
<a href="#cgiCookieString">cgiCookieString</a> and
|
|
<a href="#cgiCookieInteger">cgiCookieInteger</a> instead of
|
|
examining this string directly.
|
|
<br><dt><strong><a name="cgiAccept">char *cgiAccept</a>
|
|
</strong><br><dd>Points to a space-separated list of MIME content types
|
|
acceptable to the browser (see <a href="#cgiHeaderContentType">
|
|
cgiHeaderContentType()</a> ), or an empty string. Unfortunately, this variable
|
|
is not supplied in a useful form by most current browsers. Programmers wishing
|
|
to make decisions based on the capabilities of the browser
|
|
are advised to check the <a href="#cgiUserAgent">cgiUserAgent</a>
|
|
variable against a list of browsers and capabilities instead.
|
|
<br><dt><strong><a name="cgiUserAgent">char *cgiUserAgent</a>
|
|
</strong><br><dd>
|
|
Points to the name of the browser in use, or an empty
|
|
string if this information is not available.
|
|
<br><dt><strong><a name="cgiReferrer">char *cgiReferrer</a>
|
|
</strong><br><dd>
|
|
Points to the URL of the previous page visited by the user. This is
|
|
often the URL of the form that brought the user to your program.
|
|
Note that reporting this information is entirely up to the browser,
|
|
which may choose not do so, and may choose not to do so truthfully.
|
|
However, this variable is typically accurate. <strong>The frequently
|
|
used misspelling cgiReferer is also supplied as a macro.</strong>
|
|
<br><dt><strong><a name="cgiContentLength">int cgiContentLength</a>
|
|
</strong><br><dd>The number of bytes of form or query data received.
|
|
Note that if the submission is a form or query submission
|
|
the library will read and parse all the information
|
|
directly from cgiIn and/or cgiQueryString. The programmer should
|
|
not do so, and indeed the cgiIn pointer will be at end-of-file
|
|
in such cases.
|
|
<br><dt><strong><a name="cgiOut">FILE *cgiOut</a>
|
|
</strong><br><dd>Pointer to CGI output. The cgiHeader functions, such as
|
|
<a href="#cgiHeaderContentType">cgiHeaderContentType</a>, should
|
|
be used first to output the mime headers; the output HTML
|
|
page, GIF image or other web document should then be written
|
|
to cgiOut by the programmer using standard C I/O functions
|
|
such as fprintf() and fwrite(). cgiOut is normally equivalent
|
|
to stdout; however, it is recommended that cgiOut be used to
|
|
ensure compatibility with future versions of cgic for
|
|
specialized environments.
|
|
<br><dt><strong><a name="cgiIn">FILE *cgiIn</a>
|
|
</strong><br><dd>Pointer to CGI input. In 99.99% of cases, you will not
|
|
need this. CGIC 2.0 supports both regular POST form submissions
|
|
and multipart/form-data file upload form submissions directly.
|
|
</dl>
|
|
<H3><a name="resultcodes">cgic result code reference</a></h3>
|
|
<p>
|
|
In most cases, cgic functions are designed to produce reasonable results
|
|
even when browsers and users do unreasonable things. However, it is sometimes
|
|
important to know precisely which unreasonable things took place, especially
|
|
when assigning a default value or bounding a value is an inadequate
|
|
solution. The following result codes are useful in making this determination.
|
|
<dl>
|
|
<br><dt><strong><a name="cgiFormSuccess">cgiFormSuccess</a>
|
|
</strong><br><dd>Indicates that the function successfully performed at least one
|
|
action (or retrieved at least one value, where applicable).
|
|
<br><dt><strong><a name="cgiFormTruncated">cgiFormTruncated</a>
|
|
</strong><br><dd>Indicates that a string value retrieved from the user was
|
|
cut short to avoid overwriting the end of a buffer.
|
|
<br><dt><strong><a name="cgiFormBadType">cgiFormBadType</a>
|
|
</strong><br><dd>Indicates that a "numeric" value submitted by the user was
|
|
in fact not a legal number.
|
|
<br><dt><strong><a name="cgiFormEmpty">cgiFormEmpty</a>
|
|
</strong><br><dd>Indicates that a field was retrieved but contained no data.
|
|
<br><dt><strong><a name="cgiFormNotFound">cgiFormNotFound</a>
|
|
</strong><br><dd>Indicates that no value was submitted for a particular field.
|
|
<br><dt><strong><a name="cgiFormConstrained">cgiFormConstrained</a>
|
|
</strong><br><dd>Indicates that a numeric value was beyond the specified bounds
|
|
and was forced to the lower or upper bound as appropriate.
|
|
<br><dt><strong><a name="cgiFormNoSuchChoice">cgiFormNoSuchChoice</a>
|
|
</strong><br><dd>Indicates that the value submitted for a single-choice field
|
|
(such as a radio-button group) was not one of the acceptable values.
|
|
This usually indicates a discrepancy between the form and the program.
|
|
<br><dt><strong><a name="cgiFormEOF">cgiFormEOF</a>
|
|
</strong><br><dd>Returned by <a href="#cgiFormFileRead">cgiFormFileRead</a>
|
|
when, at the start of the call, the cgiFilePtr object is already
|
|
positioned at the end of the uploaded file data.
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|
<br><dt><strong><a name="cgiFormEOF">cgiFormIO</a>
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</strong><br><dd>Returned by <a href="#cgiFormFileRead">cgiFormFileRead</a>
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|
when an I/O error occurs while reading uploaded file data.
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|
<br><dt><strong><a name="cgiFormNotAFile">cgiFormNotAFile</a>
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|
</strong><br><dd>Returned in response to an attempt to manipulate a form field
|
|
that is not a file upload field using a file-related function.
|
|
<br><dt><strong><a name="cgiFormNoContentType">cgiFormNoContentType</a>
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|
</strong><br><dd>Returned in response to an attempt to fetch the content type of
|
|
a file-upload field when the content type is not specified by the browser.
|
|
<br><dt><strong><a name="cgiFormNoFileName">cgiFormNoFileName</a>
|
|
</strong><br><dd>Returned in response to an attempt to fetch the file name of
|
|
a file-upload field when a file name is not specified by the browser.
|
|
<br><dt><strong><a name="cgiFormOpenFailed">cgiFormOpenFailed</a>
|
|
</strong><br><dd>Returned in response to an attempt to read from a null
|
|
cgiFilePtr object, typically when the programmer has failed to
|
|
check the result of a call to <a href="#cgiFormFileOpen">cgiFormFileOpen</a>.
|
|
<br><dt><strong><a name="cgiEnvironmentMemory">cgiEnvironmentMemory</a>
|
|
</strong><br><dd>Indicates that an attempt to read or write the CGI environment
|
|
to or from a capture file failed due to an out-of-memory error.
|
|
<br><dt><strong><a name="cgiEnvironmentSuccess">cgiEnvironmentSuccess</a>
|
|
</strong><br><dd>Indicates that an attempt to read or write the CGI environment
|
|
to or from a capture file was successful.
|
|
<br><dt><strong><a name="cgiEnvironmentIO">cgiEnvironmentIO</a>
|
|
</strong><br><dd>Indicates that an attempt to read or write the CGI environment
|
|
to or from a capture file failed due to an I/O error.
|
|
<br><dt><strong><a name="cgiEnvironmentWrongVersion">cgiEnvironmentWrongVersion</a>
|
|
</strong><br><dd>Indicates that an attempt to read from a saved debugging CGI environment
|
|
produced by a pre-2.0 version of CGIC was made.
|
|
</dl>
|
|
<h3><a name="index">cgic quick index</a></h3>
|
|
<a href="#cgiAccept">cgiAccept</a> |
|
|
<a href="#cgiAuthType">cgiAuthType</a> |
|
|
<a href="#cgiContentLength">cgiContentLength</a> |
|
|
<a href="#cgiContentType">cgiContentType</a> |
|
|
<a href="#cgiEnvironmentIO">cgiEnvironmentIO</a> |
|
|
<a href="#cgiEnvironmentMemory">cgiEnvironmentMemory</a> |
|
|
<a href="#cgiEnvironmentSuccess">cgiEnvironmentSuccess</a> |
|
|
<a href="#cgiCookieInteger">cgiCookieInteger</a> |
|
|
<a href="#cgiCookies">cgiCookies</a> |
|
|
<a href="#cgiHeaderCookieSet">cgiHeaderCookieSet</a> |
|
|
<a href="#cgiHeaderCookieSetString">cgiHeaderCookieSetString</a> |
|
|
<a href="#cgiHeaderCookieSetInteger">cgiHeaderCookieSetInteger</a> |
|
|
<a href="#cgiCookieString">cgiCookieString</a> |
|
|
<a href="#cgiCookieInteger">cgiCookieInteger</a> |
|
|
<a href="#cgiHtmlEscape">cgiHtmlEscape</a> |
|
|
<a href="#cgiHtmlEscapeData">cgiHtmlEscapeData</a> |
|
|
<a href="#cgiValueEscape">cgiValueEscape</a> |
|
|
<a href="#cgiValueEscapeData">cgiValueEscapeData</a> |
|
|
<a href="#cgiFormBadType">cgiFormBadType</a> |
|
|
<a href="#cgiFormCheckboxMultiple">cgiFormCheckboxMultiple()</a> |
|
|
<a href="#cgiFormCheckboxSingle">cgiFormCheckboxSingle()</a> |
|
|
<a href="#cgiFormConstrained">cgiFormConstrained</a> |
|
|
<a href="#cgiFormDouble">cgiFormDouble()</a> |
|
|
<a href="#cgiFormDoubleBounded">cgiFormDoubleBounded()</a> |
|
|
<a href="#cgiFormEOF">cgiFormEOF</a> |
|
|
<a href="#cgiFormEmpty">cgiFormEmpty</a> |
|
|
<a href="#cgiFormEntries">cgiFormEntries</a> |
|
|
<a href="#cgiFormFileClose">cgiFormFileClose</a> |
|
|
<a href="#cgiFormFileContentType">cgiFormFileContentType</a> |
|
|
<a href="#cgiFormFileName">cgiFormFileName</a> |
|
|
<a href="#cgiFormFileOpen">cgiFormFileOpen</a> |
|
|
<a href="#cgiFormFileRead">cgiFormFileRead</a> |
|
|
<a href="#cgiFormFileSize">cgiFormFileSize</a> |
|
|
<a href="#cgiFormInteger">cgiFormInteger()</a> |
|
|
<a href="#cgiFormIntegerBounded">cgiFormIntegerBounded()</a> |
|
|
<a href="#cgiFormNoContentType">cgiFormNoContentType</a> |
|
|
<a href="#cgiFormNoFileName">cgiFormNoFileName</a> |
|
|
<a href="#cgiFormNoSuchChoice">cgiFormNoSuchChoice</a> |
|
|
<a href="#cgiFormNotAFile">cgiFormNotAFile</a> |
|
|
<a href="#cgiFormNotFound">cgiFormNotFound</a> |
|
|
<a href="#cgiFormRadio">cgiFormRadio()</a> |
|
|
<a href="#cgiFormSelectMultiple">cgiFormSelectMultiple()</a> |
|
|
<a href="#cgiFormSelectSingle">cgiFormSelectSingle()</a> |
|
|
<a href="#cgiFormString">cgiFormString()</a> |
|
|
<a href="#cgiFormStringMultiple">cgiFormStringMultiple()</a> |
|
|
<a href="#cgiFormStringNoNewlines">cgiFormStringNoNewlines()</a> |
|
|
<a href="#cgiFormStringSpaceNeeded">cgiFormStringSpaceNeeded()</a> |
|
|
<a href="#cgiFormSuccess">cgiFormSuccess</a> |
|
|
<a href="#cgiFormTruncated">cgiFormTruncated</a> |
|
|
<a href="#cgiGatewayInterface">cgiGatewayInterface</a> |
|
|
<a href="#cgiHeaderContentType">cgiHeaderContentType()</a> |
|
|
<a href="#cgiHeaderLocation">cgiHeaderLocation()</a> |
|
|
<a href="#cgiHeaderStatus">cgiHeaderStatus()</a> |
|
|
<a href="#cgiIn">cgiIn</a> |
|
|
<a href="#cgiMain">cgiMain()</a>
|
|
<a href="#cgiOut">cgiOut</a> |
|
|
<a href="#cgiPathInfo">cgiPathInfo</a> |
|
|
<a href="#cgiPathTranslated">cgiPathTranslated</a> |
|
|
<a href="#cgiQueryString">cgiQueryString</a> |
|
|
<a href="#cgiReadEnvironment">cgiReadEnvironment()</a> |
|
|
<a href="#cgiReferrer">cgiReferrer()</a> |
|
|
<a href="#cgiRemoteAddr">cgiRemoteAddr</a> |
|
|
<a href="#cgiRemoteHost">cgiRemoteHost</a> |
|
|
<a href="#cgiRemoteIdent">cgiRemoteIdent</a> |
|
|
<a href="#cgiRemoteUser">cgiRemoteUser</a> |
|
|
<a href="#cgiRequestMethod">cgiRequestMethod</a> |
|
|
<a href="#cgiScriptName">cgiScriptName</a> |
|
|
<a href="#cgiServerName">cgiServerName</a> |
|
|
<a href="#cgiServerPort">cgiServerPort</a> |
|
|
<a href="#cgiServerProtocol">cgiServerProtocol</a> |
|
|
<a href="#cgiServerSoftware">cgiServerSoftware</a> |
|
|
<a href="#cgiStringArrayFree">cgiStringArrayFree()</a> |
|
|
<a href="#cgiUserAgent">cgiUserAgent</a> |
|
|
<a href="#cgiWriteEnvironment">cgiWriteEnvironment()</a>
|
|
</body>
|
|
</html>
|