executing command - Perl Programming

Posted by wei (wei), 25 May 2007

Hi

I have some problem executing a command in my cgi script. when i execute the script in command line, the command in the script works, however when i execute the script in the browser, everything except the output of the command was shown.
any solution ?

#!/usr/bin/perl
print "Content-type: text/html\n\n";
print "<head><title>eg</title></head>\n";
print "<body>";
$command = `lsof -i`; #want to get list of open port
print "$command";
print "</body>";

thanks

Posted by admin (Graham Ellis), 25 May 2007

You apperar to have run a command and saved the results in a variable called $cmd which you never print out. But you print out a variable called $command which is never set. I think you meant to use the same variable name

Editing to add a comment. My statement above looks absurd now that the original poster has gone back and altered his code. It's really helpful to future readers if posters can refrain from later edits. I know some boards have a "no edits after 24 hours" policy enforced .... we don't, but sometimes I wonder!

Posted by wei (wei), 28 May 2007

sry a typo error...but even is the variable is the same the command still can't work

Posted by admin (Graham Ellis), 30 May 2007

I wonder if the path in the CGI environment is the same as the ordinary use path. What happens if you give the full path to "lsof"? Have you checked the return status variables?

Posted by wei (wei), 6 June 2007

if i just use the command lsof it work but if i add "-i" it won't. Is there any other ways to execute the command beside using `` ?

Posted by admin (Graham Ellis), 6 June 2007

You could open a pipe to another command and read back from it line by line .... but that's probably not going to get to the bottom of the issue

Posted by wei (wei), 9 June 2007

hi

i am able to exec the command by using exec() and making myself as the super user.

But now i have a problem, i have create a script for user to enter command to the server, so when a user enter the command and hit the button 'ok', it will execute the command at the server and display the ouput if there is any.
example... i entered "ls"
and it display the files in the folder where the script is store
then i entered "cd /root" to go to root and no ouput will be shown when the script return
after that i entered "ls" again to view files in root but the result was not the files in root but was the files in the folder where the script is store.

it seem that after cd /root was execute
it went back to the old directories instead of staying at root.

any ideas?
thank

Posted by admin (Graham Ellis), 9 June 2007

Are you running each of your exec's commands separately? If so, each will start its own process and start from the current directory.

Beware - it is very dangerous indeed to let your user enter commands that your script will exec. Don't do it!. Your should use Perl's built in functions instead, unless yo are a security guru and know exactly what you are doing. I happened to write [url=http://www.wellho.net/mouth/1225_Perl-functions-for-directory-handling.html}a short item with some source code[/url] about that this morning.

Posted by wei (wei), 10 June 2007

it seem that it was running separately, so is there a way to execute the command as a follow up of the previous command? so that for example when i had change dir, i will be able to list the files for that changed directories.

thanks

Posted by admin (Graham Ellis), 10 June 2007

Note my previous post .... it is

1. Dangerous

2. Inefficient

to do what you're doing.

But, yes, you could link them with a ";" or "\n" just as you would in shell.

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