Difference between revisions of "CGI Scripting"

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== CGI Scripting ==
 
== CGI Scripting ==
  
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We currently run Perl 5.004 and 5.6.1 for CGI scripting. We update it frequently, but anything that works under Perl 5.004 or 5.6.1 should work under any other version of Perl 5.
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We currently run Perl5 for CGI scripting. Compiled C/C++ CGI executables are allowed, along with other available language interpreters (PHP, for example).
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Wrapper CGI scripts let us give you the ability to run your own CGI scripts without compromising our security. There are few, if any limitations imposed by such wrappers (i.e. most of your scripts will work). For working examples look at http://www.he.net/faq/tutorials
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CGI scripts are a way of using programs to both generate web pages dynamically and process user input. You will need to learn a little about how to program in a Unix environment either in C or a script language like Perl.
 
CGI scripts are a way of using programs to both generate web pages dynamically and process user input. You will need to learn a little about how to program in a Unix environment either in C or a script language like Perl.
  
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You can call a program written in C from a CGI script. To compile the code on our servers, you will need to log onto the server using ssh and use the compiler GCC (GNU project C and C++ Compiler v2.4).
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You can call a program written in C/C++ as a CGI script. To compile the code on our servers, you will need to log onto the server using ssh and use the GCC compiler suite.
  
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A minor note, just so that you understand the conditions under which we support development: We provide the environment so that you can develop script and programs, however you are completely responsible for your development efforts.
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We provide the environment so that you can develop scripts and programs.  However, you are completely responsible for your development efforts.
  
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In general, when you are working on modifying an example program, which is now failing but worked when you started, go back to the example exactly, copy it, and then modify it slowly until it stops working, then you will know what you did that caused the bug.
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In general, when you are modifying an example program, which is now failing but worked when you started, go back to the example exactly, copy it, and then modify it slowly until it stops working, then you will know what you did that caused the bug.
  
 
Here are a few things to check:
 
Here are a few things to check:
  
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* Be sure to upload your scripts with your FTP client in text mode. Unix uses LF (linefeeds) to separate lines. If you are using DOS it is important the the CR LF to LF translation be done. If you are using the Mac it is important the the CR to LF translation be done. If you use a Unix-style FTP client, type "ASCII" before you send it. If you are using WS_FTP, be sure to click the ASCII radio button (and don't forget to switch back to binary before you download any executables...).
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* Be sure to upload your scripts with your SFTP client in text/ASCII mode. Unix uses LF (line feed) to as an end of line marker, Macs use a CR (carriage return) by itself, Windows/DOS uses both CR+LF. Therefore, if you're not on a Unix system, it's important to ensure that your SFTP client makes the line ending change for you. If you use a command line SFTP client, type "ASCII" before you send it. If you are using some form of GUI SFTP client, be sure that the ASCII transfer option is enabled.  Please remember to switch back to binary before you download any executables.
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* Be sure to set your script to executable. If it is a CGI script use "chmod 700". If it is a script run as a server side include use "chmod 755".
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* If your script is not a binary executable, check the first line. If your script is a Perl script the first line must be "#!/usr/bin/perl" or "#!/usr/local/bin/perl". If your script is a Bourne shell script you first line must be "#!/bin/sh". If your script is using another shell language check to make sure that the path name specified is valid. Also, make sure an extra blank line didn't get added to the top...
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* Try to run your script from the command line. This will completely test your function if it does not rely on parameters or environment variables set by the HTTPD. However, many scripts will produce runtime errors when invoked in this manner. If possible modify your script to fail politely when run at the command line so that you can use this technique to check it. Or if your are a more sophisticated programmer write a test script which sets the necessary environment variables and invokes your main script. Even if your script fails when run at the command line if it is a Perl script running it will check it for syntax errors. If it works from the command line, but fails with an error 500 when you call it, it probably is failing to open a file. Are you trying to reference your home directory with a tilde (~) in Perl? That doesn't work...
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* Check the URL or path name you are using. CGI scripts invoked as HREFs should use URLs. If your account was on thor.he.net, System CGI scripts have URLs like:
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<pre>http://thor.he.net/cgi-bin/systemscript.cgi</pre>
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User CGI scripts are invoked using slightly different URLs. For example, if your account was ''rflyer'' on the server ''thor.he.net'', the URL to invoke your script would be:
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<pre>http://thor.he.net/cgi-bin/suid/~rflyer/userscript.cgi</pre>
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If suEXEC is enabled in your account and you have a domain name, you can invoke your script directly. If the domain name for your account was squishypenguin.com, you would invoke your script with the URL:
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<pre>http://www.squishypenguin.com/cgi-bin/userscript.cgi</pre>
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You can see if suEXEC is enabled for your account by logging into the billing database at https://admin.he.net New accounts come with this feature already enabled. Select ''Edit Virtual Host Options'' and see if the ''suEXEC'' box is checked. Should you find that it is not, you can now check the box and click the "Change" button to activate the setting.
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If you have an IP Address Only account, you can substitute your IP address for the domain name. Please note that suEXEC will only work with a domain name or IP address. Make sure to substitute the correct script name, server and account name or domain name in the URL and to be sure to put your script in the directory at:
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<pre>/home/username/cgi-bin</pre>
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Server side include scripts (the "exec cmd" variety) need to use a full path name to be able to correctly locate your file. For convenience server side includes are usually put in your personal cgi-bin directory. The path name will be something like "/home/username/cgi-bin/userscript".
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* When in doubt simplify. Reduce the number of subroutines and the amount of code involved to verify that you can invoke your script at all. Then as you can prove that you are getting to a certain point start adding code back in.  
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If you get the the error message "suid attempt aborted! Reason: execve failed - Permission denied", even when using our Demo CGI, you need to make your script executable. SSH to your account, cd to the cgi-bin directory, and type:
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* Set your script to executable.  "chmod 700" will be the usual command permissions you'll want for a CGI script.
  
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<pre>chmod 700 yourscriptname</pre>
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* If your script is an interpreted script, ensure the first line of the script invokes the proper interpreter. If your script is a Perl script the first line must be "#!/usr/bin/perl" or "#!/usr/local/bin/perl". If your script is a Bourne shell script you first line must be "#!/bin/sh". If your script is using another interpreted language check to make sure that the path name specified is valid for the interpreter you're using. Also, make sure that it is the first line in the script, and that the script was uploaded in ASCII mode.
  
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This will correctly set the permissions for your script.
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* Try running your script from the command line.  This will provide a basic syntax check of your script, and possibly more, depending on how much of the code relies on parameters or environment variables set by the web server.  However, some scripts may produce run-time errors when invoked in this manner. If possible, modify your script to fail politely when run at the command line so that you can use this technique to debug it.  If you are a more sophisticated programmer, you can write a test script to set the necessary environment variables and invoke your main script.  If your script is Perl, running it from the command line will print out any syntax errors. If it works from the command line, but fails with an error 500 when you call it, it may be failing to open a file.  One common gotcha is the use of tilde (~) within a Perl script to reference your home directory.  Just use "/home/username/".
  
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You need not ask us to enable CGI scripting for your account as we provide you with your own personal cgi-bin into which you can install and modify scripts at your leisure. You do, however, need to have a Starter Virtual Host or higher account. All we ask is that you follow the guidelines on the user scripting page that can be reached from http://www.he.net/faq/tutorials The key one being respect for server resources.
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* Server side include scripts (the "exec cmd" variety) need to use a full path name to be able to correctly locate your file. For convenience server side includes are usually put in your personal cgi-bin directory. The path name will be something like "/home/username/cgi-bin/userscript".
  
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We do not offer any search scripts. You are welcome to install a CGI script to do this. There are several general database packages for Unix which could be invoked via a CGI script. You can also install your own development tools. You will need to install them into your user directory.
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* When in doubt: simplify. Reduce the number of subroutines and the amount of code involved to verify that you can invoke your script at all. Then as you can verify that you are getting to a certain point, start adding code back in.
  
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We support user CGI scripting and you can install your own form processing CGI script. [http://nms-cgi.sourceforge.net/scripts.shtml NMS FormMail] is one of many such scripts we know works with our service.
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You need not ask us to enable CGI scripting for your account as we provide you with your own personal cgi-bin into which you can install and modify scripts at your leisure. You do, however, need to have a Starter Virtual Host or higher account. All we ask is that you follow the guidelines on the user scripting page available at http://www.he.net/faq/tutorials, with the key one being respect for server resources.
  
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If you are trying to set up an imagemap and noticed we have no imagemap.conf in /httpd/conf/, be advised that we use a version of imagemap that eliminates the need for users to change a central configuration file. Every user can add their own imagemaps at their discretion without intervention from us. You are not required to email us your imagemap co-ords. You have complete and total control over your imagemap files. For more information on how to do imagemaps on our server see http://www.he.net/faq/tutorials
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We do not offer any search scripts. You are welcome to install a CGI script to do this. There are several general search packages for Unix which could be invoked via a CGI script.
  
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You can run a WAIS gateway script on your server, provided you obtained the script and installed it yourself.
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We support user CGI scripting and you can install your own form processing CGI script. [http://nms-cgi.sourceforge.net/scripts.shtml NMS FormMail] is one of many such scripts we know works with our service for handling email form processing.
  
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We have mySQL, an SQL type database, installed. There are many different publicly available CGI front-ends available for it. A mySQL database is included with all accounts. Your database name is the same as your account name. Your mySQL database should be initialized when your account is created, so that you may immediately begin using it.
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We have MySQL available to all accounts. There are many different publicly available CGI front-ends available for it. We provide [http://www.phpmyadmin.org phpMyAdmin] on version3 servers at http://yourdomain/phpmyadmin/ and https://servername.he.net/phpmyadmin/.  A MySQL database is included with all accounts. Your database name is the same as your account name. Your MySQL database is initialized when your account is created.
  
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See our mySQL FAQ or [http://mysql.he.net]mySQL Mirror Site for more information on using mySQL.
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See our MySQL FAQ or [http://mysql.he.net]MySQL Mirror Site for more information on using MySQL.
  
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Due to economic and performance considerations, we do not offer support for ASP or JSP.
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Due to performance considerations, we do not offer support for ASP or JSP.
  
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You are welcome to install your own set of additional modules. When you build modules, use the PREFIX option when generating Makefiles:
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You are welcome to install your own set of additional Perl modules. When you build modules, use the PREFIX option when generating Makefiles:
  
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<pre>perl Makefile.PL PREFIX=/home/mydir/perl</pre>
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<code>perl Makefile.PL PREFIX=/home/mydir/perl</code>
  
 
then either set the PERL5LIB environment variable before you run scripts that use the modules/libraries (see the perlrun manpage) or say:
 
then either set the PERL5LIB environment variable before you run scripts that use the modules/libraries (see the perlrun manpage) or say:
  
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<pre>use lib '/home/mydir/perl';</pre>
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<code>use lib '/home/mydir/perl';</code>

Revision as of 16:28, 9 September 2009

CGI Scripting

We currently run Perl5 for CGI scripting. Compiled C/C++ CGI executables are allowed, along with other available language interpreters (PHP, for example).

CGI scripts are a way of using programs to both generate web pages dynamically and process user input. You will need to learn a little about how to program in a Unix environment either in C or a script language like Perl.

You can call a program written in C/C++ as a CGI script. To compile the code on our servers, you will need to log onto the server using ssh and use the GCC compiler suite.

We provide the environment so that you can develop scripts and programs. However, you are completely responsible for your development efforts.

In general, when you are modifying an example program, which is now failing but worked when you started, go back to the example exactly, copy it, and then modify it slowly until it stops working, then you will know what you did that caused the bug.

Here are a few things to check:

  • Be sure to upload your scripts with your SFTP client in text/ASCII mode. Unix uses LF (line feed) to as an end of line marker, Macs use a CR (carriage return) by itself, Windows/DOS uses both CR+LF. Therefore, if you're not on a Unix system, it's important to ensure that your SFTP client makes the line ending change for you. If you use a command line SFTP client, type "ASCII" before you send it. If you are using some form of GUI SFTP client, be sure that the ASCII transfer option is enabled. Please remember to switch back to binary before you download any executables.
  • Set your script to executable. "chmod 700" will be the usual command permissions you'll want for a CGI script.
  • If your script is an interpreted script, ensure the first line of the script invokes the proper interpreter. If your script is a Perl script the first line must be "#!/usr/bin/perl" or "#!/usr/local/bin/perl". If your script is a Bourne shell script you first line must be "#!/bin/sh". If your script is using another interpreted language check to make sure that the path name specified is valid for the interpreter you're using. Also, make sure that it is the first line in the script, and that the script was uploaded in ASCII mode.
  • Try running your script from the command line. This will provide a basic syntax check of your script, and possibly more, depending on how much of the code relies on parameters or environment variables set by the web server. However, some scripts may produce run-time errors when invoked in this manner. If possible, modify your script to fail politely when run at the command line so that you can use this technique to debug it. If you are a more sophisticated programmer, you can write a test script to set the necessary environment variables and invoke your main script. If your script is Perl, running it from the command line will print out any syntax errors. If it works from the command line, but fails with an error 500 when you call it, it may be failing to open a file. One common gotcha is the use of tilde (~) within a Perl script to reference your home directory. Just use "/home/username/".
  • Server side include scripts (the "exec cmd" variety) need to use a full path name to be able to correctly locate your file. For convenience server side includes are usually put in your personal cgi-bin directory. The path name will be something like "/home/username/cgi-bin/userscript".
  • When in doubt: simplify. Reduce the number of subroutines and the amount of code involved to verify that you can invoke your script at all. Then as you can verify that you are getting to a certain point, start adding code back in.

You need not ask us to enable CGI scripting for your account as we provide you with your own personal cgi-bin into which you can install and modify scripts at your leisure. You do, however, need to have a Starter Virtual Host or higher account. All we ask is that you follow the guidelines on the user scripting page available at http://www.he.net/faq/tutorials, with the key one being respect for server resources.

We do not offer any search scripts. You are welcome to install a CGI script to do this. There are several general search packages for Unix which could be invoked via a CGI script.

We support user CGI scripting and you can install your own form processing CGI script. NMS FormMail is one of many such scripts we know works with our service for handling email form processing.

We have MySQL available to all accounts. There are many different publicly available CGI front-ends available for it. We provide phpMyAdmin on version3 servers at http://yourdomain/phpmyadmin/ and https://servername.he.net/phpmyadmin/. A MySQL database is included with all accounts. Your database name is the same as your account name. Your MySQL database is initialized when your account is created.

See our MySQL FAQ or [1]MySQL Mirror Site for more information on using MySQL.

Due to performance considerations, we do not offer support for ASP or JSP.

You are welcome to install your own set of additional Perl modules. When you build modules, use the PREFIX option when generating Makefiles:

perl Makefile.PL PREFIX=/home/mydir/perl

then either set the PERL5LIB environment variable before you run scripts that use the modules/libraries (see the perlrun manpage) or say:

use lib '/home/mydir/perl';

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