Manage all processes

ps

• This command is used to view processes running on the system.
• Usage: ps [arguments]
• Examples:
  • ps (Shows list of processes associated with the current terminal session)
  • ps aux (This is popular set of options, used to view all running processes regardless if it is or it is not associated with the current terminal session)

top

• It is used to view a continuously updating list of top processes sorted by CPU activity.
• Usage: top [arguments]
• Example:
  • top

Interrupting a program

• In a terminal, pressing CTRL+C interrupts a program.
• Many (but not all) command line programs can be interrupted by using this technique.

jobs

• Using this we can list the jobs that have been launched from our terminal.
• We can also check the job numbers of the programs.
• Usage: jobs [arguments]

bg - Backgrounding a process

• Check the job number using the jobs command.
• Usage: bg %[jobNumber]
• Example:
  • bg %1

fg - Foregrounding a process

• Check the job number using jobs command.
• Usage: fg %[jobNumber]
• Example:
  • fg %1

Stopping (Pausing) a Process

• To stop a foreground process and place it in the background, press CTRL+Z.

kill

• This command is used to send signals to programs, if no signal is mentioned the default signal is TERM (terminate).
• Usage: kill -signal PID...
• Common signals:
  • 1 (HUP) - The signal is used to indicate to programs that the controlling terminal has “hung up.”
  • 2 (INT) - Interrupt. This performs the same function as CTRL+C sent from the terminal. It will usually terminate a program.
  • 9 (KILL) - KILL. The signal is not sent to the process, infact the kernel immediately terminates the program.
  • 15 (TERM) - Terminate. This is the default signal sent by the kill command. If a program is still “alive” enough to receive signals, it will terminate.
  • 18 (CONT) - Continue. This will restore a process after a STOP or TSTP signal. This signal is sent by the bg and fg commands.
  • 19 (STOP) - Stop. This signal causes a process to pause without terminating. Like the KILL signal, it is not sent to the target process, and thus it cannot be ignored.
  • 20 (TSTP) - Terminal stop. This is the signal sent by the terminal when CTRL+Z is pressed. Unlike the STOP signal, the TSTP signal is received by the program, but the program may choose to ignore it.
• Note that signals may be specified either by number or by name, including the name prefixed with the letters SIG.
• Examples:
  • kill -1 13546
  • kill -INT 13601
  • kill -SIGINT 13601

killall

• It is used to send signals to multiple processes matching a specified program or username.
• Usage: killall [-u user] [-signal] name...
• Example:
  • killall python

reboot

• Used to reboot your device.
• Usage: sudo reboot

shutdown

• With this we can specify which of the actions to perform (halt, power down, or reboot) and provide a time delay to the shutdown event.
• Usage: sudo shutdown [arguments]
• Examples:
  • sudo shutdown -h now
  • sudo shutdown -r now