skill Command in Unix and Linux

skill Command in Unix and Linux is used to send an signals to users and process. Using skill command we can halt a user terminal or can logout him. But keep in mind that you should be root to stop other users.

There is a package called procps It includes various useful (nifty) utilities. One of such utility is skill which is responsible to send a signal to users and process such as:

Halt user terminal

Kill user and logout

Usage: skill [signal to send] [options] process selection criteria

Example: skill -KILL -v pts/*

1. To halt/stop a user called ravi

Send STOP signal to user ravi, type the following command:

[root@TechTutorial ~]# skill -STOP -u ravi

2. To resume already halted user called ravi

Send CONT signal to user ravi, type the following command:

[root@TechTutorial ~]# skill -CONT -u ravi

3. To kill and logout user called ravi

You can send KILL signal, type the following command:

[root@TechTutorial ~]# skill -KILL -u ravi

4. To kill and logout all users

type the following command:

Note: Do not run this command on any production boxes, this command just for demonstration purpose only.

[root@TechTutorial ~]# skill -KILL -v /dev/pts/*

PROCESS SELECTION OPTIONS

Selection criteria can be: terminal, user, pid, command. The options below may be used to ensure correct interpretation.

-t The next argument is a terminal (tty or pty).

-u The next argument is a username.

-p The next argument is a process ID number.

-c The next argument is a command name.

SIGNALS

The signals listed below may be available for use with skill. When known, numbers and default behavior are shown.

Name Num Action Description 0 0 n/a exit code indicates if a signal may be sent ALRM 14 exit HUP 1 exit INT 2 exit KILL 9 exit this signal may not be blocked PIPE 13 exit POLL exit PROF exit TERM 15 exit USR1 exit USR2 exit VTALRM exit STKFLT exit may not be implemented PWR ignore may exit on some systems WINCH ignore CHLD ignore URG ignore TSTP stop may interact with the shell TTIN stop may interact with the shell TTOU stop may interact with the shell STOP stop this signal may not be blocked CONT restart continue if stopped, otherwise ignore ABRT 6 core FPE 8 core ILL 4 core QUIT 3 core SEGV 11 core TRAP 5 core SYS core may not be implemented EMT core may not be implemented BUS core core dump may fail XCPU core core dump may fail XFSZ core core dump may fail

Lets see the Video of skill command in Unix and Linux