Unix - Process Management in Unix
Process Management in Unix
A process is any running program in Unix. Each process has a PID (Process ID) and runs in the foreground or background. Unix provides several commands to view, control, and manage processes.
1. ps (Process Status)
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Shows information about running processes.
ps # Shows processes in the current shell
ps -e # Shows all processes
ps -f # Full format (with UID, PPID, start time, etc.)
ps aux # Shows all processes with detailed info
Example Output:
USER PID %CPU %MEM COMMAND
root 1 0.0 0.1 init
user 1023 1.5 2.3 firefox
2. top (Real-Time Process Viewer)
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Displays running processes in real time, like a task manager.
top # Starts live process monitor
htop # (if installed) a user-friendly version of top
You can see CPU usage, memory usage, and interactively kill processes inside top.
3. kill (Send Signal to Process)
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Used to stop or control processes by sending signals.
kill 1234 # Kill process with PID 1234 (sends SIGTERM by default)
kill -9 1234 # Force kill (sends SIGKILL)
kill -STOP 1234 # Pause process
kill -CONT 1234 # Resume paused process
4. jobs (List Background Jobs)
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Shows background processes started in the current shell.
sleep 100 & # Run in background
jobs # List background jobs
Example output:
[1]+ Running sleep 100 &
5. fg (Foreground)
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Brings a background job back to the foreground.
fg %1 # Bring job 1 to the foreground
6. bg (Background)
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Resumes a suspended job in the background.
sleep 200 # Run normally
^Z # Press Ctrl+Z to suspend
bg # Resume job in background
7. Workflow Example
sleep 300 & # Start process in background
jobs # See it listed
kill %1 # Kill job 1
Or:
sleep 500
^Z # Suspend with Ctrl+Z
bg # Continue in background
jobs # See it running
fg %1 # Bring it back to foreground
✅ Summary:
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ps→ Snapshot of processes -
top→ Live monitoring -
kill→ Send signals to processes -
jobs→ List jobs in current shell -
fg→ Bring job to foreground -
bg→ Resume job in background
