lsof redirect

WRXSTi · 10-02-2006, 11:22 AM

I'm trying to redirect the output of lsof from fileA.sh called by a cronjob, but it fails to do so.

fileA.sh contains the following.
echo **** my active listings ****
lsof -l

crontab -u root -l
* * * * * /home/root/fileA.sh /home/root/fileB.log

fileB.log contains the echo output, but not the losf.... why ?

jxi · 10-02-2006, 11:36 AM

maybe you need the redirection sign '>'

* * * * * /home/root/fileA.sh > /home/root/fileB.log

Or perhaps lsof is putting output in stderr, so,

* * * * * /home/root/fileA.sh 2>&1 > /home/root/fileB.log

WRXSTi · 10-02-2006, 11:46 AM

Quote:

* * * * * /home/root/fileA.sh 2>&1 > /home/root/fileB.log

no luck still not written to fileB.log

If I run from the cmd line

sh fileA.sh > fileB.log

it will write the output of lsof to fileB.log, however via cronjob it does not.

jxi · 10-02-2006, 12:11 PM

ok first, not to be overly critical, but where did /home/root come from? You're free to have such a path, but it's just unusual. Assuming that's in fact present (as opposed to, say, /root), then what is the output of :

/home/root/fileA.sh
/home/root/fileA.sh 2>file.err ; cat file.err

are you running the bash shell? (echo $SHELL)

Markie1006 · 10-02-2006, 12:16 PM

Quote:

Originally Posted by WRXSTi

no luck still not written to fileB.log

If I run from the cmd line

sh fileA.sh > fileB.log

it will write the output of lsof to fileB.log, however via cronjob it does not.

Common mistake - the 2>&1 needs to go at the end.

Code:

 * * * * * /home/root/fileA.sh > /home/root/fileB.log 2>&1

From the O'Reilly Unix Power Tools book

Quote:

1. $ cat food 2>&1 >file

On the first command line, the shell sees 2>&1 first. That means "make the standard error (file descriptor 2) go to the same place as the standard output (fd1) is going." There's no effect because both fd2 and fd1 are already going to the terminal. Then >file redirects fd1 (stdout) to file. But fd2 (stderr) is still going to the terminal.

2. $ cat food >file 2>&1

On the second command line, the shell sees >file first and redirects stdout to file. Next 2>&1 sends fd2 (stderr) to the same place fd1 is going - that's to the file. And that's what you want.

jxi · 10-02-2006, 12:39 PM

Quote:

the 2>&1 needs to go at the end.

thanks Markie1006! (I just confirmed it with a test. Makes sense actually)

WRXSTi · 10-02-2006, 12:58 PM

Yes I'm using bash shell.

/home/root is a actually /home/xroot, but used /home/root for simplicty... bad example.

so I changed the crojob to
* * * * * sh fileA.sh > fileB.log 2>&1

lsof still not written to fileB.log

*********** ACTIVE FILES
fileA.sh: line 3: lsof: command not found

again I can run it

./fileA.sh

fine from the cmd line.

WRXSTi · 10-02-2006, 01:22 PM

I changed to

/usr/sbin/lsof

in fileA.sh and it now works !! few...

thx guys !

Markie1006 · 10-02-2006, 03:45 PM

Just as an addendum.

cron typically doesn't import the environment the way a normal login shell does, so it won't have the PATH setup for instance.
For this reason, you should always fully qualify any external commands in scripts that are going to be run from cron.