You're running a script, command, whatever.. You don't expect it to take long, now 5pm has rolled around and you're ready to go home... Wait, it's still running... You forgot to nohup it before running it... Suspend it, send it to the background, then disown it... The ouput wont go anywhere, but at least the command will still run... Show Sample Output

Very useful in shell scripts because you can run a task nicely in the background using job-control and output progress until it completes. Here's an example of how I use it in backup scripts to run gpg in the background to encrypt an archive file (which I create in this same way). $! is the process ID of the last run command, which is saved here as the variable PI, then sleeper is called with the process id of the gpg task (PI), and sleeper is also specified to output : instead of the default . every 3 seconds instead of the default 1. So a shorter version would be sleeper $!; The wait is also used here, though it may not be needed on your system. echo ">>> ENCRYPTING SQL BACKUP" gpg --output archive.tgz.asc --encrypt archive.tgz 1>/dev/null & PI=$!; sleeper $PI ":" 3; wait $PI && rm archive.tgz &>/dev/null Previously to get around the $! not always being available, I would instead check for the existance of the process ID by checking if the directory /proc/$PID existed, but not everyone uses proc anymore. That version is currently the one at http://www.askapache.com/linux-unix/bash_profile-functions-advanced-shell.html but I plan on upgrading to this new version soon. Show Sample Output

This command runs your shell script in the background with no output of any kind, and it will remain running even after you logout.

Press ^Z, do what you need to do on the shell, then input % to resurrect the suspended job.

Chronic Bash function: chronic 3600 time # Print the time in your shell every hour chronic 60 updatedb > /dev/null # update slocate every minute Note: use 'jobs' to list background tasks and fg/bg to take control of them.

background and disown, but with a proper one-line syntax

List background jobs, grep their number - not process id - and then kill them Show Sample Output

Execute commands serially on a list of hosts. Each ssh connection is made in the background so that if, after five seconds, it hasn't closed, it will be killed and the script will go on to the next system. Maybe there's an easier way to set a timeout in the ssh options...

Cleaned up and silent with &>/dev/null at the end. Show Sample Output

Like this you can continue a suspended job without blocking again your terminal

Ummmm.. Saw that gem on some dead-head hippies VW bus at phish this summer.. It's actually one of my favorite ways of using bash, very clean. It shows what you can do with the cool advanced features like job control, redirection, combining commands that don't wait for each other, and the thing I like the most is the use of the ( ) to make this process heirarchy below, which comes in very handy when using fifos for adding optimization to your scripts or commands with similar acrobatics. F UID PID PPID WCHAN RSS PSR CMD 1 gplovr 30667 1 wait 1324 1 -bash 0 gplovr 30672 30667 - 516 3 \_ sleep 3 1 gplovr 30669 1 wait 1324 1 -bash 0 gplovr 30673 30669 - 516 0 \_ sleep 5 1 gplovr 30671 1 wait 1324 1 -bash 0 gplovr 30674 30671 - 516 1 \_ sleep 7 Show Sample Output

Actually $! is an internal variable containing PID of the last job in background. More info: http://tldp.org/LDP/abs/html/internalvariables.html#PIDVARREF Using $! for job control: possibly_hanging_job & { sleep ${TIMEOUT}; eval 'kill -9 $!' &> /dev/null; }