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Ian
Asked: 2012-10-05 16:34:11 +0800 CST

Seeing what background process is up to

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I currently have a background process on my unix server that's running hours longer than it should be.

I can't remember the command to allow me to see the output of a background process. I'll remember to bookmark this answer!

unix

4 Answers

  1. Best Answer

    What also might be useful if you're uncertain whether it's doing anything at all, is use 'strace'.

    If your app is the 'dhcpd' service, run ps ax | grep [d]hcpd

    $ ps axufw | grep [d]hcpd
dhcpd    21645  0.0  0.1  19156  4956 ?        Ss   Oct02   0:00 /usr/sbin/dhcpd -f -q -4 -pf /run/dhcp-server/dhcpd.pid -cf /etc/ltsp/dhcpd.conf

    Your PID is 21645, so you'd run sudo strace -p 21645. Or drop the 'sudo' if you're root already.

    It will get the system calls from your application in real time and tell you precisely what your program is doing.

    Note: Wrap a letter of the grep command in a bracket to strain out the grep command itself.

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  2. As a follow up to Mariano Montañez Ureta.

    If you can see the task in the jobs window, all you should be able to see something like this:

    $ jobs
[1]+  Running                 tail -f .ssh/known_hosts &

    If you then use the fg command coupled with the job number you can bring that to the foreground, i.e. fg %1 would bring my tail command to the foreground. You can also use the fg command with a PID.

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  3. use fg wich means foreground :)

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  4. tail -f whatever-file-the-process-is-writing-to.txt
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