Linux系统命令无法通过crontab在Perl脚本中使用

Question

I have added a script in crontab for every 30 minutes. The line goes as follows:

  */30 * * * * root perl /root/perl.pl

The above script has a execution of system command 'top' and it gets printed in a log file.

If I run it manually it runs fine. But while running it via crontab, it does not show up the desired results. Please can somebody help me with this. Thank you.

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The command in the above perl script is:

 $top = `sudo top`;

The error I am getting is:

sudo: sorry, you must have a tty to run sudo

I changed my command from sudo to visudo. But still the problem remains.

Answer 1

You should use the full path in cron (and use which perl to find the full path):

*/30 * * * * root /usr/bin/perl /root/perl.pl 

OR better yet, make the script executable using chmod +x , and add the interpreter to the beginning of the script #!/usr/bin/perl -w and call it directly from cron

*/30 * * * * root /root/perl.pl 

Also if there is a problem in the perl script, you could output the result from cron like this

*/30 * * * * root /root/perl.pl > /tmp/myscript.log

Answer 2

You should look into the requiretty setting with regard to visudo. Look for a line that reads Defaults requiretty . You could try commenting it out, but you will be sacrificing some security. See man sudoers .

You could also try running top in batch mode with one iteration:

$top = `sudo top -bn1`;

Batch mode option is for sending output to other programs.