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Job Control: Background and Foreground

Jobs are processes you start from your terminal. You can run them in background. Bring them to foreground. Manage them.

Here's the thing: Job control lets you multitask. Run multiple things. Switch between them.

Running in Background​

Start in Background​

command &                          # Run in background
./script.sh &                      # Script in background

Real example:

$ sleep 60 &
[1] 12345
$

Job [1], PID 12345. Terminal is free.

My take: Use & to background processes. Keep terminal free.

Move to Background​

# Start command
python app.py

# Press Ctrl+Z to suspend
# Then:
bg                                 # Resume in background

My take: Ctrl+Z suspends. bg backgrounds. Useful when you forget &.

Managing Jobs​

jobs: List Jobs​

jobs                               # List jobs
jobs -l                            # With PIDs

Output:

[1]  + running    sleep 60
[2]  - stopped    python app.py

States:

  • + = Current job
  • - = Previous job
  • running = Active
  • stopped = Suspended

My take: jobs shows background jobs. Use it to see what's running.

fg: Bring to Foreground​

fg                                 # Current job
fg %1                              # Job 1
fg %2                              # Job 2

My take: fg brings jobs to foreground. See output. Interact with them.

bg: Run in Background​

bg                                 # Current job
bg %1                              # Job 1

My take: bg runs suspended jobs in background. Use after Ctrl+Z.

nohup: Survive Terminal Close​

nohup command > output.log 2>&1 &

What it does: Runs in background. Survives terminal close. Output to file.

The 2>&1: Redirects errors to same place as output.

My take: Use nohup for long-running processes. They keep running after you disconnect.

Common Patterns​

Start and Background​

./long_script.sh &

Start and Detach​

nohup ./script.sh > output.log 2>&1 &

Suspend and Background​

# Start command
python app.py
# Press Ctrl+Z
bg                                 # Run in background

Common Mistakes (I've Made These)​

  1. Forgetting &: Process blocks terminal. Add & to background.

  2. Not using nohup: Process dies when terminal closes. Use nohup for long-running.

  3. Losing track of jobs: Use jobs to see what's running.

  4. Killing wrong job: Check job number. Don't kill wrong thing.

  5. Not redirecting output: Background jobs need output redirected. Use > file.log 2>&1.

Real-World Examples​

Run Script in Background​

./deploy.sh > deploy.log 2>&1 &

Check Background Jobs​

jobs
fg %1                              # Bring to foreground if needed

Long-Running Process​

nohup python app.py > app.log 2>&1 &

What's Next?​

Now that you can control jobs, you can multitask. Or learn about Process Control for more process management.

Personal note: When I started, I'd let processes block my terminal. Then I learned job control. Now I background everything. Terminal stays free. Job control is essential.