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Job Control to Background And Foreground Command In Bash2 min read

Ağu 16, 2020 2 min

Job Control to Background And Foreground Command In Bash2 min read

Okunur: 2 dakika

Appending an & (ampersand) to any command run within bash will
background the process.

for count in $(seq 1 10); do
    sleep 10m &
done
[1] 17
[2] 18
[3] 19
[4] 20
[5] 21
[6] 22
[7] 23
[8] 24
[9] 25
[10] 26

Will background 10 processes which will simply sleep for 10 minutes. Bash will return a table of job ids and their PIDs.

To list a table which shows all background processes use the built-in
jobs command.

$ jobs -l
job management, bash job control, bash background worker, iş yönetimi

You can also use ps to list the background processes by requesting the
processes which have the parent pid of your current bash shell.

$ ps -O user --ppid $$
bash job management, bash ile iş yönetmi, arka planda iş çalıştırma

By using ps we can refer to important information on the processes.

To connect to one of the background processes, use fg and the job id
number.

fg 5
job management, bash job control, bash background worker, iş yönetimi

To put job 5 back into the background you first have to suspend the
process by using ^Z (Control-Z) and then running bg specifying the job
id.

$ fg 5
sleep 10m
^Z
[11]+  Stopped                 sleep 10m
$ bg 5
[11]+ sleep 10m &

To put fg, bg and ^Z to practical use, lets say you were copying a large
directory which was going to take a long time though you wanted to
regain control of your current shell.

Suspend the current command using ^Z.

$ cp -a /opt/backups/files/hourly.0 /opt/restore
^Z
[1]+  Stopped                 cp -a /opt/backups/files/hourly.0 /opt/restore

Background the task with bg referring to the job id in the table.

$ bg 5
[1]+ cp -a /opt/backups/files/hourly.0 /opt/restore &

Confirm the process is running with ps.

$ ps -O user --ppid $$
PID USER     S TTY          TIME COMMAND
45 mertcan     D tty1   00:00:16 cp -a /opt/backups/files/hourly.0 /opt/restore

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