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kill.2freebsd

BSD mandoc

NAME

kill - send signal to a process

LIBRARY

Lb libc

SYNOPSIS

In sys/types.h In signal.h Ft int Fn kill pid_t pid int sig

DESCRIPTION

The Fn kill system call sends the signal given by Fa sig to Fa pid , a process or a group of processes. The Fa sig argument may be one of the signals specified in sigaction(2) or it may be 0, in which case error checking is performed but no signal is actually sent. This can be used to check the validity of Fa pid .

For a process to have permission to send a signal to a process designated by Fa pid , the real or effective user ID of the receiving process must match that of the sending process or the user must have appropriate privileges (such as given by a set-user-ID program or the user is the super-user). A single exception is the signal SIGCONT, which may always be sent to any process with the same session ID as the caller.

If Fa pid is greater than zero

The Fa sig signal is sent to the process whose ID is equal to Fa pid .

If Fa pid is zero

The Fa sig signal is sent to all processes whose group ID is equal to the process group ID of the sender, and for which the process has permission; this is a variant of killpg(2).

If Fa pid is -1

If the user has super-user privileges, the signal is sent to all processes excluding system processes (with P_SYSTEM flag set), process with ID 1 (usually init(8)), and the process sending the signal. If the user is not the super user, the signal is sent to all processes with the same uid as the user excluding the process sending the signal. No error is returned if any process could be signaled.

For compatibility with System V, if the process number is negative but not -1, the signal is sent to all processes whose process group ID is equal to the absolute value of the process number. This is a variant of killpg(2).

RETURN VALUES

Rv -std kill

ERRORS

The Fn kill system call will fail and no signal will be sent if:

Bq Er EINVAL

The Fa sig argument is not a valid signal number.

Bq Er ESRCH

No process can be found corresponding to that specified by Fa pid .

Bq Er ESRCH

The process id was given as 0 but the sending process does not have a process group.

Bq Er EPERM

The sending process is not the super-user and its effective user id does not match the effective user-id of the receiving process. When signaling a process group, this error is returned if any members of the group could not be signaled.

SEE ALSO

getpgrp(2), getpid(2), killpg(2), sigaction(2), raise(3), init(8)

STANDARDS

The Fn kill system call is expected to conform to St -p1003.1-90 .

HISTORY

The Fn kill function appeared in AT&T System v7 .