nohup

A background process can continue its execution even after the user has logged out. Usually, all processes terminate at the time of logout. But if the background process is begins with a    nohup command, the background process could still be continued.

The nohup utility invokes the named command with the arguments supplied.   Whenever the command is invoked, nohup arranges for the Hangup signal that intimates the process to hangup, to be ignored through the process. nohup can be used whenever it is known in which command will take a long time to run and the user needs to logout of the terminal; when a shell  exits,  the  system  sends  its  children hangup  signals, that by default cause them to be killed.

Syntax

nohup command [arguments]

All running, stopped, and background jobs will ignore hangup signal and continue running, if their invocation is preceded through the nohup command. The output of the nohup command is captured in a file known as nohup.out if standard output is a terminal and if the current directory is writable.

The following instance dispalys the usage of the nohup command.

# nohup ls -Rl / > /tmp/out & [1] 1101

# exit

On logging in again it could be seen in that the command which has been issued is active.