Daily Drivers

kill

Usage       : kill -9 <PID>
Example     : kill -9 1234
Description : Terminate processes by PID.
Takeaway    : Use when you need to forcefully stop a specific process.

pkill

Usage       : pkill firefox
Example     : Kill all Firefox processes.
Description : Kill processes by name or attributes.
Takeaway    : Use when you want to terminate processes without looking up PIDs.

killall

Usage       : killall nginx
Example     : Stop all nginx processes.
Description : Kill processes by name (all instances).
Takeaway    : Use for stopping multiple processes of the same name.

Process Priority

nice

Usage       : nice -n 10 command
Example     : nice -n 15 gzip largefile
Description : Start a process with adjusted priority.
Takeaway    : Use to run tasks with lower priority to avoid hogging resources.

renice

Usage       : renice -n 5 -p 1234
Example     : Increase priority of process 1234.
Description : Change priority of a running process.
Takeaway    : Use to adjust performance of active processes.

psnice

Usage       : psnice -n 10 -p 5678
Example     : Lower priority of process 5678.
Description : Adjust process priority (similar to renice).
Takeaway    : Use for fine-grained priority control.

chrt

Usage       : chrt -r -p 1234
Example     : Assign real-time priority to process 1234.
Description : Set real-time scheduling policies.
Takeaway    : Use for advanced scheduling control.

Job Control

jobs

Usage       : jobs
Example     : Show running background tasks.
Description : List background jobs in the shell.
Takeaway    : Use to manage shell background processes.

fg

Usage       : fg %1
Example     : Resume job 1 in foreground.
Description : Bring background job to foreground.
Takeaway    : Use to interact with background jobs.

bg

Usage       : bg %1
Example     : Move job 1 to background.
Description : Resume job in background.
Takeaway    : Use to continue tasks without blocking terminal.

nohup

Usage       : nohup command &
Example     : nohup python script.py &
Description : Run process immune to hangups.
Takeaway    : Use for long-running jobs that survive logout.

disown

Usage       : disown %1
Example     : Disown job 1.
Description : Detach job from shell.
Takeaway    : Use to prevent jobs from being killed when shell exits.

setsid

Usage       : setsid command
Example     : setsid ./server
Description : Run process in new session.
Takeaway    : Use to detach processes from terminal session.

Debugging & Tracing

pgrep

Usage       : pgrep nginx
Example     : Get PID of nginx.
Description : Find processes by name.
Takeaway    : Use for quick PID lookup.

strace

Usage       : strace -p 1234
Example     : Debug process 1234.
Description : Trace system calls of a process.
Takeaway    : Use for diagnosing system call issues.

ltrace

Usage       : ltrace ./program
Example     : Debug shared library usage.
Description : Trace library calls.
Takeaway    : Use for debugging dynamic library interactions.

Task Scheduling

at

Usage       : echo "command" | at 5pm
Example     : Run backup at 5pm.
Description : Schedule one-time tasks.
Takeaway    : Use for delayed task execution.

atd

Usage       : systemctl start atd
Example     : Ensure at jobs run.
Description : Daemon for at jobs.
Takeaway    : Use to enable scheduled jobs.

atq

Usage       : atq
Example     : Show pending tasks.
Description : List scheduled jobs.
Takeaway    : Use to monitor scheduled jobs.

atrm

Usage       : atrm <jobid>
Example     : Cancel job 2.
Description : Remove scheduled jobs.
Takeaway    : Use to manage scheduled tasks.

batch

Usage       : echo "command" | batch
Example     : Run heavy job during idle time.
Description : Run tasks when system load is low.
Takeaway    : Use for deferred execution based on load.

Miscellaneous

skill

Usage       : skill -u user
Example     : Kill all processes of user.
Description : Kill processes interactively (like kill).
Takeaway    : Use for user-based process termination.