Most of the time you login into remote server via ssh. If you start a shell script or command and you exit (abort remote connection), the process / command will get killed. Sometime job or command takes a long time. If you are not sure when the job will finish, then it is better to leave job running in background. However, if you logout the system, the job will be stopped. What do you do?
nohup command
Answer is simple, use nohup utility which allows to run command./process or shell script that can continue running in the background after you log out from a shell:
nohup Syntax:
nohup command-name &Where,
- command-name : is name of shell script or command name. You can pass argument to command or a shell script.
- & : nohup does not automatically put the command it runs in the background; you must do that explicitly, by ending the command line with an & symbol.
nohup command examples
1) Login to remote server
2) Execute script called pullftp.sh
Type exit or press CTRL + D exit from remote server.
3) Find all programs and scripts with setuid bit set on, enter:
Type exit or press CTRL + D exit from remote server.
Please note that nohup does not change the scheduling priority of COMMAND; use nice for that:
As you can see nohup keep processes running after you exit from a shell. Read man page of nohup and nice command for more information. Please note that nohup is almost available on Solaris/BSD/Linux/UNIX variant.
$ ssh user@remote.server.com2) Execute script called pullftp.sh
# nohup pullftp.sh &Type exit or press CTRL + D exit from remote server.
# exit3) Find all programs and scripts with setuid bit set on, enter:
# nohup find / -xdev -type f -perm +u=s -print > out.txt &Type exit or press CTRL + D exit from remote server.
# exitPlease note that nohup does not change the scheduling priority of COMMAND; use nice for that:
# nohup nice -n -5 ls / > out.txt &As you can see nohup keep processes running after you exit from a shell. Read man page of nohup and nice command for more information. Please note that nohup is almost available on Solaris/BSD/Linux/UNIX variant.
Update:
# 1: As pointed out by Jason you can use at command to queue a job for later execution. For example, you can run pullftp.sh script to queue (one minute) later execution
# 2: You can also use screen command for same. Brock pointed out disown shell internal command for same purpose. Here is how you can try it out:
# 1: As pointed out by Jason you can use at command to queue a job for later execution. For example, you can run pullftp.sh script to queue (one minute) later execution
$ echo "pullftp.sh" | at now + 1 minute# 2: You can also use screen command for same. Brock pointed out disown shell internal command for same purpose. Here is how you can try it out:
$ pullftp.sh &
$ disown -h
$ exitReference or Source: http://www.cyberciti.biz/tips/nohup-execute-commands-after-you-exit-from-a-shell-prompt.html
This is a complete copy from the source.
Aditional Info: less Nohup.out
Provides you with the output of the <command&>. This is some thing similar to tail -f on a live log file.
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