- Which CGI script languages does FastVirtual
support?
- Which operating system and web server does
FastVirtual use?
- Where should I upload my CGI scripts?
- What is the actual URL of my "cgi-bin"
directory?
- What paths should I use to the various directories?
- How should I specify the location of Perl?
- How should I specify the location of sendmail?
- What system utilities can I use in my Perl
scripts?
- Do I need to change (chmod) file permissions? How do I
change file permissions?
- Do my CGI scripts have to be in the "cgi-bin"
directory?
- Which Perl modules are available?
- My script is generating an internal server error.
What could be causing this?
- My browser displays the source code. Why isn't my
CGI script executing?
- How can I compile my C source file into an
executable?
- I can't find the "cgi-t" directory. Where is it
located?
- How can I include output from a CGI script in a
web page? Can I use Server Side Includes (SSI) to do this?
- Am I permitted to use file locking?
- What is the best way to generate a random number
in Perl?
- Perl states that a "literal @ now requires a
backslash". What does this mean?
- How can I get CGI support from FastVirtual?
 Which
CGI script languages does FastVirtual support?
FastVirtual supports many
interpreted programming languages. The most widely used is Perl 5. Compiled
C is also supported.
- FastVirtual uses Perl version 5.008006
- The compiler is GCC 2.95.4 20020320 [FreeBSD]
Perl 5 is commonly accepted the standard for CGI development on
the Web, and is our preferred programming language. Scripts
developed in other languages, such as sh and tcl, will likely function correctly, but
Perl remains our preference; particularly for support reasons.
Which
operating system and web server does FastVirtual use?
- FastVirtual uses FreeBSD 4.11-RELEASE-p25. ELF binaries are
supported.
- Our web server is a modified version of Apache 1.3.33
(UNIX), with standard CGI/1.1 interface. FastVirtual does not
support WinCGI.
Where
should I upload my CGI scripts?
You should upload your CGI scripts to the "cgi-bin" directory.
This directory is located in your
document root.
What
is the actual URL of my "cgi-bin" directory?
Scripts in your "cgi-bin" directory are available at the same
location on your domain via URL:
http://www.yourdomain.com/cgi-bin/yourscript.cgi
The URL is the same for scripts you wish to access via your secure server:
https://www.yourdomain.com/cgi-bin/yourscript.cgi
What
paths should I use to the various directories?
The physical path to your home directory is "/drive/home/username".
The absolute path is "/usr/home/yourdomain.com".
As there is no guarantee that the physical or absolute path names
will always remain as above, and in the interest of making your code
as portable as possible (i.e. not dependent on the configuration of
any single web server), it is wise to use the the DOCUMENT_ROOT variable
in place of absolute paths.
| Description |
Path |
| Home directory: |
Absolute path:
/usr/home/yourdomain.com
Recommended path:
$ENV{'DOCUMENT_ROOT'}/..
Standards-compliant approach:
$homedir = $ENV{'DOCUMENT_ROOT'};
$homedir =~ s/\/htdocs$// || die; |
| Document root: |
Absolute path:
/usr/home/yourdomain.com/htdocs
Recommended path:
$ENV{'DOCUMENT_ROOT'} |
| "cgi-bin" directory: |
Absolute path:
/usr/home/yourdomain.com/htdocs/cgi-bin
Recommended path:
$ENV{'DOCUMENT_ROOT'}/cgi-bin |
How
should I specify the location of Perl?
Perl is located at "/usr/local/bin/perl". The first line of all
Perl scripts should always be:
#!/usr/local/bin/perl
FastVirtual uses Perl 5.008006. When developing your scripts, you
should run "perl -v" to confirm you are using the same version.
How
should I specify the location of sendmail?
Sendmail can be found at "/usr/sbin/sendmail". On BSD-based UNIX platforms
this is the default location. FastVirtual strongly recommends that
you use the "-t" option (i.e. "sendmail -t"), as this provides
additional security and functionality.
A typical Perl script might use sendmail as follows:
$to_addr = 'you\@yourdomain.com';
$from_addr = 'them\@theirdomain.com';
$subject = 'Message subject';
$message_body = <<EOT;
Type your message content here.
EOT
open MAIL, "|/usr/sbin/sendmail -t";
print MAIL "To: $to_addr\n";
print MAIL "From: $from_addr\n";
print MAIL "Subject: $subject\n";
print MAIL "\n"; print MAIL "$message_body\n";
close MAIL;
Note: The common "|/usr/sbin/sendmail $recipient"
method for invoking sendmail contains a security hole, and is
strongly discouraged.
What
system utilities can I use in my Perl scripts?
Perl provides many efficient system utilities. Consider using the
following Perl commands as opposed to system calls or back-ticks, as
this will improve your script's performance.
| Command |
Standard System Call |
Perl Method |
| date |
$mydate = `/bin/date`; |
$mydate = localtime;
|
| grep |
@results = `grep $string
$filename`; |
open FILE, "$filename";
@lines = <FILE>;
close FILE;
@results = grep($string, @lines); |
| ls |
@files = `ls -la $path`; |
opendir(DIR, $path);
@files = readdir(DIR);
closedir(DIR); |
| mkdir |
system("mkdir $dir"); |
mkdir $dir, 0777; |
| mv |
system("mv $oldname $newname"); |
rename $oldname, $newname; |
| rm |
system("rm $file"); |
unlink $file; |
| rmdir |
system("rmdir $dir"); |
rmdir $dir; |
Note: C has similar utilities to Perl. Check your favorite C
resource for details.
Do
I need to change (chmod) file permissions? How do I change file
permissions?
Permissions for CGI scripts should be changed to be executable by the
web server. You can do this by using an FTP program (i.e. CuteFTP),
or by using Webby, FastVirtual's online file editor.
The server utility for specifying/changing file permissions is
called "chmod". This should be listed as an option in your FTP
program.
File permissions for executable files should be set to 0755:
| Type |
Permissions |
| USER |
read, write, execute
|
| GROUP |
read, execute |
| OTHER |
read, execute |
File permissions for data files should be set to 0660:
| Type |
Permissions |
| USER |
read, write |
| GROUP |
read, write |
| OTHER |
none |
If you wish to install a 3rd-party script,
please be sure to follow the instructions provided by the developer.
Particularly, ensure you set the correct permissions on the
applicable directories and files.
Note: FastVirtual does not support group-writable or
world-writable permissions.
Do
my CGI scripts have to be in the "cgi-bin" directory?
The web server expects to find CGI scripts in the "cgi-bin"
directory. FastVirtual does not recommend placing your scripts
outside of this directory.
This unsupported method may work: Place following entry in your
.htaccess file:
AddType application/x-httpd-cgi pl cgi
Although this may work, it is not efficient, and FastVirtual does
not provide support for problems that may result from
this configuration change.
The recommended approach is to use
META Refresh or Server
Side Includes to redirect to, or include output from scripts
located in your "cgi-bin" directory.
Which
Perl modules are available?
Please see our list of currently installed
Perl
Modules. The list is periodically updated, so may not contain
recent additions.
My
script is generating an internal server error. What could be causing
this?
An internal server error is returned by the server
when your script fails to generate the correct CGI header. This is a
non-specific error, so there are several possible causes:
If your script was written in Perl, this may have been uploaded
as a binary file. Perl files should be uploaded in ASCII mode, so
you may need to add .pl (or .cgi) extensions as ASCII file types to
your FTP software.
Your script may contain errors.
If your script was written in Perl, run your script through our syntax checker, available through
your account control panel. The syntax checker will identify any
errors or typos and allow you to fix them.
If you are writing your own scripts in Perl, download
Perl Win32. This will allow you to execute your scripts from the
command prompt, which will help you debug your code before uploading
to your domain.
You may not have set correct permissions for your script files.
Please see this FAQ.
Your script could be dying before it prints a correct CGI header.
Your error logs may assist you in identifying the problem.
If your script is a binary executable (i.e. compiled C), please
check to ensure it is in a FreeBSD-compatible binary format. Windows
binaries (.exe files) cannot execute on FreeBSD.
Your script may be exceeding CGI resource limits, so may have
been killed by the server. This applies to scripts that use large
amounts of memory or CPU cycles, stay in execution too long, or
erroneous scripts that fall into a loop.
Scripts which fall into an endless loop, use large
amounts of memory, use large numbers of CPU cycles, or stay in execution
too long are subject to being killed by the web server. Per-process
limits are as follows:
| Resource |
Limit |
| CPU time: |
60 seconds |
| Memory usage: |
16 MB |
| Concurrent CGI processes: |
16 (per account) |
Check your script's CGI header to ensure this being generated
correctly. If your script is written in Perl, add this code to the
beginning of your script:
#!/usr/local/bin/perl
print "Content-type: text/plain ";
select(STDOUT);
$| = 1;
open(STDERR, ">&STDOUT");
print "Script execution is starting now...";
You should not use "die", as this writes to STDERR and
not STDOUT. Instead, print out a proper header and error message,
and then exit.
If you've followed these instructions and still can't get your script
to work, you may be interested in our CGI Support Options.
My
browser displays the source code. Why isn't my CGI script executing?
In order for the server to execute your CGI script, it needs to
be uploaded to your "cgi-bin" directory (or a subdirectory thereof).
If your script is located elsewhere on your site, then the script
won't execute and you will only see the code.
For scripts that need to be compiled, be sure to compile your
script before attempting to execute it. If you attempt to execute a
source file (i.e. "myscript.c"), you will only see the code.
How
can I compile my C source file into an executable?
You may upload your precompiled C executables whenever you wish.
If you want FastVirtual to compile your C source file, please upload
the file to your account and send us the filename and location. If
your script requires more than one source file, you will also need
to upload a BSD-compatible makefile.
FastVirtual provides two complimentary compiles for each account.
If you require additional compiles, please see CGI Support Options below for pricing information.
I
can't find the "cgi-t" directory. Where is it located?
This is an internal directory that is used for FastVirtual's
web tools and other complementary scripts. The directory is hidden
and cannot be accessed. All scripts that are proceeded by "cgi-t/"
are preinstalled and can be configured via your account control
panel.
You are welcome to use our complementary scripts, as well as your
own custom CGI scripts.
How
can I include output from a CGI script in a web page? Can I use Server
Side Includes (SSI) to do this?
Yes, you can use Server Side Includes to include CGI script
output in your web pages. Your page needs to end with a ".shtml"
extension, which tells the server to look for SSI instructions. SSI
will not work on a ".html" page.
Simply include the following code on the .shtml page where you
want the script output to appear (where "myscript.cgi" is the name
of your script):
<!--#include virtual="/cgi-bin/myscript.cgi" -->
More information about SSI, including details of all supported
variables, can be found in our
Server Side Includes Guide.
Am
I permitted to use file locking?
Yes, you may use file locking. However, you should note that the
server will kill any process that has been on a file lock for more
than a few seconds. In this situation, the server will return an
internal server error.
A typical Perl script might use file locking as follows:
$LOCK_EX = 2;
$LOCK_UN = 8;
sub lock {
flock MBOX, $LOCK_EX;
# in case someone appended while we are waiting...
seek MBOX, 0, 2;
}
sub unlock {
flock MBOX, $LOCK_UN;
}
open MBOX, ">>myfile.txt";
lock();
print MBOX "message\n";
unlock();
What
is the best way to generate a random number in Perl?
Use the "rand" function. Perl calls "srand" with a "good" seed
the first time you call rand, even if you haven't called "srand"
yourself.
Perl
states that a "literal @ now requires a backslash". What
does this mean?
In Perl, the "@" character is actually an array symbol, so you need
to precede this with a backslash like so: "\@".
How
can I get CGI support from FastVirtual?
Before proceeding further, make sure you have checked your script using the
above troubleshooting tips.
The script developer
may help you install and configure your script. Make sure you
describe the problem in detail, and include the URL of this page.
Before you contact the developer, make sure you read through any
readme files that were included with your script.
Due to the inherently complex nature of CGI development, CGI
support is subject to charges. FastVirtual provides the following
CGI support options:
Script Configuration Service - If you've installed your
Perl script, but are having trouble configuring it, we can configure
your script for you. Send us the name and location of the script,
together with your configuration requirements, and we will complete
the configuration for a one-time fee of $70.00. If we cannot
complete the configuration, you will not be billed.
Custom Development Service - If you need to develop a custom
Perl script, our development team is ready to help. Standard CGI
programming is billed at $150.00
per hour. Systems-level development is billed at higher rates. Please
contact us for a detailed quote.
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