Why aren't system() calls working?

hotyopa has asked for the wisdom of the Perl Monks concerning the following question:

Hi All,

As an addendum to this question:

I have written the following admittedly dangerous script:

#!/usr/bin/perl

use CGI;

$q = new CGI;


$directory = '/home/httpd/html/antonh/testdir';

print $q->header, $q->start_html, "Removing $directory<br>";
$result = system("rm -r $directory");

print -W $directory,",", -o $directory,",",$result;
[download]

This is the result I get on the screen:

Removing /home/httpd/html/antonh/testdir
1,1,256

This script does work from the command line, but for some reason the system call is failing. I had similar problems trying to do a chmod in the same way.

Any ideas why this might be the case?

Comment on Why aren't system() calls working? Download Code

Replies are listed 'Best First'.
Re: Why aren't system() calls working? by ChOas (Curate) on Dec 15, 2000 at 11:46 UTC
Hey... The return of the system call is in the upper 8 bits of the 16 returned, so you might be better off with something like: `system("rm -r $directory"); $result=$? >> 8;` [download] and cough running with strict, -w and -T cough double cough you could have tried perldoc -f system double cough GreetZ!, ChOas :wq And I should keep my mouth shut, coz I didn't answer the REAL question, sorry... you might wanna check the permissions of files/directory/parent dir rm -rf might force it	[reply] [d/l]
Re: Why aren't system() calls working? by chipmunk (Parson) on Dec 15, 2000 at 20:15 UTC
I wonder why you are using system() and not Perl's builtin rmdir() function. `$result = rmdir($directory); if ($result) { print "Directory '$directory' removed.\n"; } else { print "Directory '$directory' not removed: $!\n"; }` [download] Or, if you need to do a recursive rm, you can use File::Path's rmtree method. If your code works from the command line but not via the web server, there must be some difference between the users or the environments. Note that, in order to delete a directory, you must have write access to that directory and its parent directory.	[reply] [d/l]
Re: Why aren't system() calls working? by eg (Friar) on Dec 15, 2000 at 11:47 UTC
My guess is that the user your web-server is running as (nobody or www-data, most likely) doesn't have the proper permissions to do anything to your test directory. If you `chmod 777` it from your command line, then the script ought to work from a browser. Note, perl itself has a rmdir command, although you'd have to clear out the directory first (using File::Find or something.) Huh? I thought you said the script ran fine from the command line, therefore I would hope that you somehow have permissions to play around with the test directory. Nevertheless, a second thing you might check is to make sure that `rm` is in the script's path. Better yet, use a full path in your system call. Have you checked the server's error log? What (if anything) does it say?	[reply]
If I could I would by hotyopa (Scribe) on Dec 15, 2000 at 11:51 UTC
As per the earlier question, I can't chmod it from the command line because I'm not the owner and don't have root access... Also, the UID and GID that the script are running under are the owners of the directory and all files within.	[reply]
Re: Why aren't system() calls working? by Fastolfe (Vicar) on Dec 15, 2000 at 20:39 UTC
As another poster mentioned, you're not quite fetching the error status correctly. As it is now, if `$result` is non-zero, it's indicating a failure (counter to the usual behavior). In addition, your server's error logs should contain a textual description of why the 'rm' command failed (as it would have printed its message to STDERR, which would have gone to the server's error logs). While you're debugging, you may want to make use of CGI::Carp to send your errors straight to the browser: `use CGI::Carp 'fatalsToBrowser';` [download]	[reply] [d/l] [select]


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