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After you execute a command (or shell script) in the background using
&, if you logout from the session, the command will get killed. To avoid
that, you should use nohup as shown below.
If $INBACK is set, command will launch in foreground and inverse.
Very useful in script !
We could apply the inverse comportement like that :
eval command ${INBACK:+&}
Check out the usage of 'trap', you may not have seen this one much. This command provides a way to schedule commands at certain times by running them after sleep finishes sleeping. In the example 'sleep 2h' sleeps for 2 hours. What is cool about this command is that it uses the 'trap' builtin bash command to remove the SIGHUP trap that normally exits all processes started by the shell upon logout. The 'trap 1' command then restores the normal SIGHUP behaviour.
It also uses the 'nice -n 19' command which causes the sleep process to be run with minimal CPU.
Further, it runs all the commands within the 2nd parentheses in the background. This is sweet cuz you can fire off as many of these as you want. Very helpful for shell scripts.
This is helpful for shell scripts, I use it in my custom php install script to schedule to delete the build files in 3 hours, as the php install script is completely automated and is made to run slow.
Does require at, which some environments without crontab still do have.
You can add as many commands to the at you want. Here's how I delete them in case the script gets killed. (trapped)
atq |awk '{print $1}'|xargs -iJ atrm J &>/dev/null
This command runs your shell script in the background with no output of any kind, and it will remain running even after you logout.