Apache/CGI
CGI scripts
editThe CGI (Common Gateway Interface) is a norm permitting Apache to execute some programs, which can be written in any programming language (Bash, C, Java, Perl, PHP, Python...), from the moment it's executable and it respects certain in/out constraints.
Configure the CGI scripts access
editTo make Apache interpret the scripts, it's necessary to do a minimum of settings in the site configuration.
ScriptAlias
editThe directive (from httpd.conf):
ScriptAlias /cgi-bin/ ''/scripts path/''
precise the folder name where Apache is authorized to executer the CGI scripts.[1]
Unix example:
ScriptAlias /cgi-bin/ /var/www/cgi-bin
Windows example, use the URL format (no backslash):
ScriptAlias /cgi-bin/ "C:/wamp/bin/apache/apache2.2.27/cgi-bin/"
Actually the path /cgi-bin/
doesn't really exist, it's redirected to the scripts path, set by the directive, and it allows to write some URL like http://server/cgi-bin/my_script
.
ExecCGI
editThe following clause activates the option ExecCGI
in /var/www/cgi-bin
, which authorize Apache to execute some scripts on the server:
<Directory /var/www/cgi-bin>
Options ExecCGI
</Directory>
For example, if a script is called essai.cgi
into /home/httpd/cgi-bin
:
<Directory /home/httpd/cgi-bin>
Options ExecCGI
</Directory>
Then, call the URL: http://serveur/cgi-bin/essai.cgi
AddHandler
editThis clause permits to choose the files extensions which will be authorized, eg:
AddHandler cgi-script .cgi .exe .pl .py .vbs
Recapitulation
editFull example on Windows, in the Apache configuration:
ScriptAlias /cgi-bin/ "E:/www/cgi-bin/"
<Directory "E:/www/cgi-bin/">
Options FollowSymLinks Indexes
AllowOverride All
Order deny,allow
Allow from all
Require all granted
</Directory>
In E:/www/cgi-bin/.htaccess
:
AddHandler cgi-script .cgi .exe .pl .py .vbs
Write a CGI program
editThe main constraint concerns the program outputs. If a CGI script generates some data on its standard output, he must display an HTTP header before, allowing to identify them.
Bash
edit#!/bin/bash
# Header
echo "Content-type: text/html"
# Header end
echo ""
# Content to display in the navigator
echo "<html><body>Hello World!</body></html>"
This script generates an HTML page.
Perl
edit#!c:/perl/perl/bin/perl.exe -w
use CGI;
my $query = new CGI;
my $Name = $query->param('Name');
print $query->header();
print "Hello World!"
Python
edit#!C:\Program Files (x86)\Python\python.exe
# -*- coding: UTF-8 -*-
print "Content-Type: text/plain;charset=utf-8"
print
print "Hello World!"
VBS
editFor Windows.[2]
'!c:/windows/system32/cscript //nologo
Wscript.Echo "Content-type: text/html" & vbLF & vbLF
WScript.Echo "Hello World!"
Wscript.Quit 0
Known errors
edit- Error 500 Server error!: replace a
Deny from all
by aAllow from all
.
or
# setsebool -P httpd_enable_cgi 1 # chcon -R -t httpd_sys_script_exec_t cgi-bin/your_script.cgi
- Error 403 Forbidden access: impossible to list this folder, so call directly its files.
- If the file source code is appearing in the navigator: the .htaccess is not properly set.
- couldn't create child process: replace the path after shebang. For example:
#!/usr/bin/perl
par#!c:/perl/perl/bin/perl.exe -w
.#!/usr/bin/env python
par#!C:\Program Files (x86)\Python\python.exe
.
- End of script output before headers: missing header (eg: move the importation before
print "Content-Type: text/plain;charset=utf-8"
). But it can also be the symptom of a compilation error in the script language. - malformed header from script: Bad header: : the header is not adapted (eg: replace
#print "Content-Type: text/plain;charset=utf-8"
byprint "Content-type: text/html\n\n"
if there is aprint "<html>"
after).
Otherwise consult the Apache logs...