• Perl/UNIX .profile problem
• Unix Aliases?
• Perl Script Not Working With Crontab
• Twig in a crontab?
• Running Perl program w/root privs via cron
• system call in crontab
• Perl & cron job environmental variables
• http://www.cyberciti.biz/faq/how-do-i-add-jobs-to-cron-under-linux-or-unix-oses/# HowTo: Add Jobs To cron Under Linux or UNIX?
• http://216.147.18.102/unixfaq/cron.shtml# Unix FAQ - Cron
• http://andrew-gray.com/unixfaq/cron.shtml# Unix FAQ - Cron

  Cron jobs do not inherit the login environment of the user

  Cron jobs do not have a stdin associated with them

  ...

• http://cronfaq.com/# Cron Frequently Asked Questions
• http://www.kerp.net/cronjob/faq.html# Cron Job FAQ
• http://linux.about.com/od/linux101/l/blnewbie3_3_3.htm# Basic Linux Operations FAQ
• http://tldp.org/LDP/lame/LAME/linux-admin-made-easy/using-cron.html# Automating Tasks with Cron and Crontab files
• http://www.tldp.org/LDP/intro-linux/html/sect_04_04.html# 4.4. Scheduling processes

So you're having an error. First thing you should do is check what error happened.

• What error does ls the command output to STDERR?
• What error does system report?

Likely cause: The current directory isn't what you think it is, and you don't have access to write to the current directory.

#!/usr/bin/perl
# a.pl 

use strict;
use warnings;

system("ls -lrt > /tmp/a.out");
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Hi, Thanks for the reply. Definitely works whatever you have suggested. However, if I execute a shell script with "at" command like below #b.sh at -f a.pl now it doesnt work. The system command in the perl script is not recognized. Can you please try your end.. Thanks, Gulla

See Re: system command is not working and figure it out

Check the ENV/cwd, check the permissions, check the logs, repeat

where is the time specification for your "at" comand?. It seems that your script waits forever

I agree with pvaldes, it seems like you are not using at correctly. In fact, I'm surprised at is not returning an error immediately. I have tried three Unix flavors and get an error when I do not specify a time.

me@myaixbox:/home/me/sandbox
$ at -f 1.pl
at: 0481-110 Command usage error; a parameter is missing.
me@myaixbox:/home/me/sandbox
$ uname
AIX
[download]

me@mylinuxbox:~/sandbox
$ at -f 1.pl
Garbled time
me@mylinuxbox:~/sandbox
$ uname
Linux
[download]

userid@somebox:/tmp/tmp.66
# at -f 1.pl
bad time specification
userid@somebox:/tmp/tmp.66
# uname
HP-UX
[download]

Hello Friends, Thanks for your replies. In fact , the "at" command which I place in my reply earlier inlucdes the "now" at the end. I am sorry that it got merged with the sentense. The actual command in the script is "at -f a.pl now" Thanks, Gulla

Use <c></c> tags to delimit code or screen scrapes. See How do I post a question effectively?

I can recreate your problem now.

me@mybox:/home/me/sandbox
$ cat 1.pl
#!/usr/bin/perl
system('echo bob >/tmp/blarney.out');
me@mybox:/home/me/sandbox
$ ./1.pl
me@mybox:/home/me/sandbox
$ cat /tmp/blarney.out
bob
me@mybox:/home/me/sandbox
$ rm /tmp/blarney.out
me@mybox:/home/me/sandbox
$ at -f 1.pl now
Job me.1323356661.a will be run at Thu Dec  8 10:04:21 EST 2011.
me@mybox:/home/me/sandbox
$ at -l
me@mybox:/home/me/sandbox
$ ls -l /tmp/blarney.out
ls: 0653-341 The file /tmp/blarney.out does not exist.
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When I check my mail, I see the problem. Notice the "command not found" message. This means you must supply full path to the script.

me@mybox:/home/me/sandbox
$ mail
Mail [5.2 UCB] [AIX 5.X]  Type ? for help.
"/var/spool/mail/me": 2 messages 1 new 2 unread
 U  1 daemon            Thu Dec  8 10:02  32/950  "Output from at job 
+1.pl, me"
>N  2 daemon            Thu Dec  8 10:04  31/940  "Output from at job 
+1.pl, me"
? 1
Message  1:
From daemon Thu Dec  8 10:02:08 2011
Date: Thu, 8 Dec 2011 10:02:08 -0500
From: daemon
To: me
Subject: Output from at job 1.pl, me@mybox, exit status 127

Cron Environment:
 SHELL = /opt/freeware/bin/bash
 PATH=/usr/bin:/etc:/usr/sbin:/usr/bin/X11:/sbin:/usr/java14/jre/bin:/
+usr/java14/bin:/usr/local/bin
 CRONDIR=/var/spool/cron/crontabs
 ATDIR=/var/spool/cron/atjobs
 LOGNAME=me
 HOME=/home/me

Your "at" job executed on mybox on Thu Dec  8 10:02:08 EST 2011
1.pl


produced the following output:

bash: line 3: 1.pl: command not found


*****************************************************************
        cron: The previous message is the standard output
        and standard error of one of the cron commands.
[download]

Now with full path supplied.

me@mybox:/home/me/sandbox
$ ls -l /tmp/blarney.out
ls: 0653-341 The file /tmp/blarney.out does not exist.
me@mybox:/home/me/sandbox
$ at -f /home/me/sandbox/1.pl now
Job me.1323356887.a will be run at Thu Dec  8 10:08:07 EST 2011.
me@mybox:/home/me/sandbox
$ at -l
me@mybox:/home/me/sandbox
$ ls -l /tmp/blarney.out
-rw-r-----    1 me users             4 Dec 08 10:08 /tmp/blarney.out
[download]

Kudos for running it all down, aren't logs magical?

:D

Thanks for the detailed analysis and step by step walk through.

I tried the way you have advised. However, this time my error file says that "/sbin/sh: system: not found". Below is the code I tried,

--------
#a.pl

#!/usr/bin/perl

system('ls -lrt > a.out');

--------

Comand 
$ at -f /tmp/a.pl now

commands will be executed using /sbin/sh
job 1323397408.a at Fri Dec  9 13:23:28 2011

Error:

/sbin/sh: system: not found
[download]

I am wondering why the external system command is not recognized in the perl.

Any thoughts my friend. When the perl script is executed with "At" command, it invokes a shell to execute the script. However, that shell is unable to recoginse the system command. Is that correct??

Please let me know what else I can try to resolve this issue.

Thanks In Advance

I am wondering why the external system command is not recognized in the perl.

The error is reported by /bin/sh, not perl. For some reason, the shell tries to interpret the script. Is the #!/usr/bin/perl line really the first one in your script?