I am a new Linux and Unix shell user. How do I Remove or delete jobs from current bash / ksh or POSIX based shell?
Job control is nothing but the ability to stop/suspend the execution of processes (command) and continue/resume their execution as per your requirements. This is done using your operating system and shell such as bash/ksh or POSIX shell.[donotprint]
[/donotprint]You need to use bg command to restart a stopped background process. The fg command moves a background job in the current shell environment into the foreground. To delete/remove jobs or to tell the shell not to send a HUP signal use disown command. This command is part of bash or ksh93 shell.
Remove jobs from the table of active job.
The basic syntax is as follows:
disown jobID1 jobID2 ... jobIDN
disown [options] jobID1 jobID2 ... jobIDN
A note about BASH and KSH93 disown command => The disown command on ksh shell causes the shell not to send a HUP signal to each given job, or all active jobs if job is omitted, when a login shell terminates. =>The disown command on bash shell can either remove jobs or causes the shell not to send a HUP signal to each given job or all jobs. => All examples, on this page are executed on bash shell either on OS X Unix or Ubuntu Linux.
disown command examples
Before you start using fg command, you need to start couple of jobs on your system for demonstration purpose. Type the following commands to start jobs:
 – jobID for process number (PID) 4581 for command ‘xeyes’
 – jobID for process number (PID) 4584 for command ‘ping sxi.io’
Without any options, each jobID is removed from the table of active jobs i.e. the bash shell uses its notion of the current job which is displayed by + symbol in jobs -l command: $ disown Sample outputs:
How do I remove all jobs?
Pass the -a option to disown command, type: $ disown -a ## You should not see any jobs running on screen ## $ jobs -l
How do I remove only running jobs?
Pass the -r option to disown command, type: $ disown -r $ jobs -l
How do I keep running job after I exit from a shell prompt in background?
The SIGHUP (Hangup) signal is used by your system on controlling terminal or death of controlling process. You can use SIGHUP to reload configuration files and open/close log files too. In other words if you logout from your terminal all running jobs will be terminated. To avoid this you can pass the -h option to disown command. This option mark each jobID so that SIGHUP is not sent to the job if the shell receives a SIGHUP. The syntax is: $ disown -h jobID $ disown -h %2 Job IDs begin with the % character; %n identifies job n, while %% identifies the current job. In this following example, update the Debian or Ubuntu Linux based server using apt-get command in background:
## Step 1: update system ##apt-get upgrade&>/root/system.update.log &## Step 2: Mark apt-get so that SIGHUP is not sent when you exit and go for tea ##disown-h## Step 3: exit from root shell ##exit
## Step 1: update system ##
apt-get upgrade &> /root/system.update.log & ## Step 2: Mark apt-get so that SIGHUP is not sent when you exit and go for tea ##
disown -h ## Step 3: exit from root shell ##
The author is the creator of nixCraft and a seasoned sysadmin, DevOps engineer, and a trainer for the Linux operating system/Unix shell scripting. Get the latest tutorials on SysAdmin, Linux/Unix and open source topics via RSS/XML feed or weekly email newsletter.