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kill

send a signal to a process


  1. kill.1.man
  2. kill.2.man


1. kill.1.man

Manpage of KILL

KILL

Section: Linux User's Manual (1)
Updated: November 21, 1999
Index Return to Main Contents
 

NAME

kill - send a signal to a process

 

SYNOPSIS

kill [ -signal | -s signal ] pid ...
kill [ -L | -V, --version ]
kill -l [ signal ]

 

DESCRIPTION

The default signal for kill is TERM. Use -l or -L to list available signals. Particularly useful signals include HUP, INT, KILL, STOP, CONT, and 0. Alternate signals may be specified in three ways: -9 -SIGKILL -KILL. Negative PID values may be used to choose whole process groups; see the PGID column in ps command output. A PID of -1 is special; it indicates all processes except the kill process itself and init.

 

SIGNALS

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

NameNumActionDescription
00n/aexit code indicates if a signal may be sent
ALRM14exit
HUP1exit
INT2exit
KILL9exitcannot be blocked
PIPE13exit
POLLexit
PROFexit
TERM15exit
USR1exit
USR2exit
VTALRMexit
STKFLTexitmight not be implemented
PWRignoremight exit on some systems
WINCHignore
CHLDignore
URGignore
TSTPstopmight interact with the shell
TTINstopmight interact with the shell
TTOUstopmight interact with the shell
STOPstopcannot be blocked
CONTrestartcontinue if stopped, otherwise ignore
ABRT6core
FPE8core
ILL4core
QUIT3core
SEGV11core
TRAP5core
SYScoremight not be implemented
EMTcoremight not be implemented
BUScorecore dump might fail
XCPUcorecore dump might fail
XFSZcorecore dump might fail

 

NOTES

Your shell (command line interpreter) may have a built-in kill command. You may need to run the command described here as /bin/kill to solve the conflict.

 

EXAMPLES

kill -9 -1
Kill all processes you can kill.
kill -l 11
Translate number 11 into a signal name.
kill -L
List the available signal choices in a nice table.
kill 123 543 2341 3453
Send the default signal, SIGTERM, to all those processes.

 

SEE ALSO

pkill(1), skill(1), kill(2), renice(1), nice(1), signal(7), killall(1).

 

STANDARDS

This command meets appropriate standards. The -L flag is Linux-specific.

 

AUTHOR

Albert Cahalan <albert@users.sf.net> wrote kill in 1999 to replace a bsdutils one that was not standards compliant. The util-linux one might also work correctly.

Please send bug reports to <procps-feedback@lists.sf.net>


 

Index

NAME
SYNOPSIS
DESCRIPTION
SIGNALS
NOTES
EXAMPLES
SEE ALSO
STANDARDS
AUTHOR

This document was created by man2html using the manual pages.
Time: 17:31:22 GMT, October 23, 2013

2. kill.2.man

Manpage of KILL

KILL

Section: Linux Programmer's Manual (2)
Updated: 2009-09-15
Index Return to Main Contents
 

NAME

kill - send signal to a process  

SYNOPSIS

#include <sys/types.h>

#include <signal.h> int kill(pid_t pid, int sig);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

kill(): _POSIX_C_SOURCE >= 1 || _XOPEN_SOURCE || _POSIX_SOURCE  

DESCRIPTION

The kill() system call can be used to send any signal to any process group or process.

If pid is positive, then signal sig is sent to the process with the ID specified by pid.

If pid equals 0, then sig is sent to every process in the process group of the calling process.

If pid equals -1, then sig is sent to every process for which the calling process has permission to send signals, except for process 1 (init), but see below.

If pid is less than -1, then sig is sent to every process in the process group whose ID is -pid.

If sig is 0, then no signal is sent, but error checking is still performed; this can be used to check for the existence of a process ID or process group ID.

For a process to have permission to send a signal it must either be privileged (under Linux: have the CAP_KILL capability), or the real or effective user ID of the sending process must equal the real or saved set-user-ID of the target process. In the case of SIGCONT it suffices when the sending and receiving processes belong to the same session.  

RETURN VALUE

On success (at least one signal was sent), zero is returned. On error, -1 is returned, and errno is set appropriately.  

ERRORS

EINVAL
An invalid signal was specified.
EPERM
The process does not have permission to send the signal to any of the target processes.
ESRCH
The pid or process group does not exist. Note that an existing process might be a zombie, a process which already committed termination, but has not yet been wait(2)ed for.
 

CONFORMING TO

SVr4, 4.3BSD, POSIX.1-2001.  

NOTES

The only signals that can be sent to process ID 1, the init process, are those for which init has explicitly installed signal handlers. This is done to assure the system is not brought down accidentally.

POSIX.1-2001 requires that kill(-1,sig) send sig to all processes that the calling process may send signals to, except possibly for some implementation-defined system processes. Linux allows a process to signal itself, but on Linux the call kill(-1,sig) does not signal the calling process.

POSIX.1-2001 requires that if a process sends a signal to itself, and the sending thread does not have the signal blocked, and no other thread has it unblocked or is waiting for it in sigwait(3), at least one unblocked signal must be delivered to the sending thread before the kill() returns.  

Linux Notes

Across different kernel versions, Linux has enforced different rules for the permissions required for an unprivileged process to send a signal to another process. In kernels 1.0 to 1.2.2, a signal could be sent if the effective user ID of the sender matched that of the receiver, or the real user ID of the sender matched that of the receiver. From kernel 1.2.3 until 1.3.77, a signal could be sent if the effective user ID of the sender matched either the real or effective user ID of the receiver. The current rules, which conform to POSIX.1-2001, were adopted in kernel 1.3.78.  

BUGS

In 2.6 kernels up to and including 2.6.7, there was a bug that meant that when sending signals to a process group, kill() failed with the error EPERM if the caller did have permission to send the signal to any (rather than all) of the members of the process group. Notwithstanding this error return, the signal was still delivered to all of the processes for which the caller had permission to signal.  

SEE ALSO

_exit(2), killpg(2), signal(2), sigqueue(2), tkill(2), exit(3), capabilities(7), credentials(7), signal(7)  

COLOPHON

This page is part of release 3.32 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
CONFORMING TO
NOTES
Linux Notes
BUGS
SEE ALSO
COLOPHON

This document was created by man2html using the manual pages.
Time: 17:31:22 GMT, October 23, 2013

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