Background Processes

Run commands in the background while continuing to use the shell.

Basic Usage

Add & at the end of a command:

#> long_running_command &
[1] 12345
#>

The shell prints:

#> jobs
[1]  Running    sleep 100 &
[2]  Running    make &

#> fg %1
# Job 1 now in foreground

#> bg %1
# Continues job 1 in background

#> kill %1

#> kill 12345

When a background job completes:

[1]  Done       sleep 10 &

make &
# Continue working while make runs

command1 &
command2 &
command3 &
# All three run simultaneously

long_command > output.log 2>&1 &
# Run in background, save output to file

noisy_command &> /dev/null &

Background processes have stdin disconnected from terminal:

cat &
# Will receive EOF immediately

Background processes:

When exiting with running jobs:

#> exit
hash: There are running jobs.
#> exit
# Second exit forces quit

make clean && make &
# Edit files while building

curl -O http://example.com/large-file.zip &

python -m http.server 8000 &

tail -f /var/log/syslog &

jobs
# or
ps aux | grep command

command &
pid=$!
# Do other work...
wait $pid
echo "Command finished"

For jobs that should survive logout:

nohup long_command &
# Output goes to nohup.out