Use the kill command to send a signal to each process specified by a pid (process identifier). The default signal is SIGTERM (terminate the process).
Syntax
kill PID
kill -s signalName PID
kill -9 PID
Common UNIX Signal Names and Numbers
All available UNIX signals have different names, and are mapped to certain numbers as described below.
| Number | Name | Description | Used for |
|---|
| 0 | SIGNULL | Null | Check access to pid |
| 1 | SIGHUP | Hangup | Terminate; can be trapped |
| 2 | SIGINT | Interrupt | Terminate; can be trapped |
| 3 | SIGQUIT | Quit | Terminate with core dump; can be |
| 9 | SIGKILL | Kill | Forced termination; cannot be trapped |
| 15 | SIGTERM | Terminate | Terminate; can be trapped |
| 24 | SIGSTOP | Stop | Pause the process; cannot be trapped |
| 25 | SIGTSTP | Terminal | stop Pause the process; can be |
| 26 | SIGCONT | Continue | Run a stopped process |
Note the specific mapping between numbers and signals can vary between Unix
implementations, please see the manual page entry signal(5), by typing
the following command:
man 5 signal
Examples: Send a Kill Single To Process ID 1414
Use the following command to kill pid 4242 and exit gracefully:
kill 4242
To find pid of any job or command use ps command:
ps | grep command
ps aux | grep command
ps aux | grep apache
The following all are equivalent commands with -9 SIGKIL (i.e forcefully kill 1414 process):
kill -s SIGKILL 1414
kill -s KILL 1414
kill -s 9 1414
kill -SIGKILL 1414
kill -KILL 1414
Find out or determine if process pid is running
The easiest way to find out is run ps aux command and grep process
name. If you got output along with process name/pid, your process is
running.
Task: Find out process pid
Simply use ps command as follows:
ps aux | grep {process-name}
For example find out if mysqld process (mysqld pid) is running or not:
$ ps aux | grep mysqld
Output:
mysql 28290 1.1 2.7 340496 56812 ? Sl Jul31 348:27 /usr/libexec/mysqld --defaults-file=/etc/my.cnf --basedir=/usr --datadir=/var/lib/mysql --user=mysql --pid-file=/var/run/mysqld/mysqld.pid --skip-locking --socket=/var/lib/mysql/mysql.sock
Find the process ID of a running program using pidof
pidof command finds the process id’s (pids) of the named programs. It prints those id’s on screen. This program is on some systems used in run level change scripts, especially when the system has a System-V like rc structure. In that case these scripts are located in /etc/rc?.d, where ? is the runlevel. If the system has a start-stop-daemon (8) program that should be used instead.
# pidof mysqld
Output:
28290
(cyberciti.biz)
