kill(2) [osx man page]

KILL(2) 						      BSD System Calls Manual							   KILL(2)

NAME

     kill -- send signal to a process

SYNOPSIS

     #include <signal.h>

     int
     kill(pid_t pid, int sig);

DESCRIPTION

     The kill() function sends the signal specified by sig to pid, a process or a group of processes.  Typically, Sig will be one of the signals
     specified in sigaction(2).  A value of 0, however, will cause error checking to be performed (with no signal being sent).	This can be used
     to check the validity of pid.

     For a process to have permission to send a signal to a process designated by 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 descendant of the current process.

     If pid is greater than zero:
	     Sig is sent to the process whose ID is equal to pid.

     If pid is zero:
	     Sig 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 pid is -1:
	     If the user has super-user privileges, the signal is sent to all processes excluding system processes 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

     Upon successful completion, a value of 0 is returned.  Otherwise, a value of -1 is returned and errno is set to indicate the error.

ERRORS

     Kill() will fail and no signal will be sent if:

     [EINVAL]		Sig is not a valid, supported signal number.

     [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.

     [ESRCH]		No process or process group can be found corresponding to that specified by pid.

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

SEE ALSO

     getpgrp(2), getpid(2), killpg(2), sigaction(2)

STANDARDS

     The kill() function is expected to conform to IEEE Std 1003.1-1988 (``POSIX.1'').

4th Berkeley Distribution					  April 19, 1994					 4th Berkeley Distribution

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kill(2) System Calls Manual kill(2)

Name
kill - send signal to a process

Syntax
#include <sys/types.h>
#include <signal.h>

kill(pid, sig)
pid_t pid;
int sig;

Description
The system call sends the signal sig to a process specified by the process number pid. The sig can be a signal specified in a call or it
can be 0. If the sig is 0, error checking is performed, but a signal is not sent. This call can be used to check the validity of pid.

The sending and receiving processes must have the same effective user ID, otherwise this call is restricted to the superuser with the
exception of the signal SIGCONT. The signal SIGCONT can always be sent to a child or grandchild of the current process.

If the process number is 0, the signal is sent to all other processes in the sender's process group.

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.

The above two options are variants of

If the process number is -1, and the user is the superuser, the signal is broadcast for all processes except to system processes and the
process sending the signal.

Processes may send signals to themselves.

Environment
System Five
POSIX

When your program is compiled in the System V or POSIX environment, a signal is sent if either the real or effective uid of the sending
process matches the real or saved-set-uid (as described in ) of the receiving process. In addition, any process can use a pid of -1, and
the signal is sent to all processes subject to these permission checks.

In POSIX mode, the pid argument is of type pid_t.

Return Values
Upon successful completion, a value of 0 is returned. Otherwise, a value of -1 is returned, and is set to indicate the error.

Diagnostics
The system call fails under the following conditions:

[EINVAL] The sig is not a valid signal number.

[EPERM] The sending process is not the superuser, and its effective user ID does not match the effective user ID of the receiving
process.

[ESRCH] No process can be found corresponding to that specified by pid.

See Also
execve(2), getpgrp(2), getpid(2), killpg(2), sigvec(2), pause(3)

kill(2)

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kill(2) [osx man page]

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