kill.txt

# politely ask process to stop
$ kill 1234
# shoot process in the head
$ kill -9 1234

Usage:
  kill [-<signal>] <pid>
  kill -l [name/number]

# kill is used to send signals to running processes (by pid)
# By default it sends SIGTERM (15) which politely asks the process to stop.
# Signal 9 or SIGKILL (or KILL) halts the process impolitely.
# Specified signals follow a '-'. A signal can be the name, short name or number.

# To suspend and then continue a process (to eg temporarily halt a running cronjob),
# use 19 (SIGSTOP) and 18 (SIGCONT):
# Suspend ...
$ kill -19 12345
# ... and continue.
$ kill -18 12345

# Suspending a parent process will _not_ suspend it's children!
#   `pstree -p` can be useful to find the exact PID to use.

# these all do the same:
kill -15 123, kill -SIGTERM 123, kill -TERM 123

# list signals (supply a number to get signal name, or vice versa)
$ kill -l [number/name]

# tip: partial PIDs can be tab-completed (on sane systems, anyway)

See also: $ man 7 signal
          https://en.wikipedia.org/wiki/Signal_(IPC)