Mac Developer Library Developer


This manual page is part of Xcode Tools version 5.0

To obtain these tools:

If you are running a version of Xcode Tools other than 5.0, view the documentation locally:

  • In Xcode

  • In Terminal, using the man(1) command

Reading manual pages

Manual pages are intended as a quick reference for people who already understand a technology.

  • To learn how the manual is organized or to learn about command syntax, read the manual page for manpages(5).

  • For more information about this technology, look for other documentation in the Apple Developer Library.

  • For general information about writing shell scripts, read Shell Scripting Primer.

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

     kill -- send signal to a process

     #include <signal.h>

     kill(pid_t pid, int sig);

     The kill() function sends the signal specified by sig to pid, a process or a group of processes.  Typi-cally, Typically,
     cally, 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

     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 appropri-ate appropriate
     ate privileges (such as given by a set-user-ID program or the user is the super-user).  A single excep-tion exception
     tion 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).

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

     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

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

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

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

Reporting Problems

The way to report a problem with this manual page depends on the type of problem:

Content errors
Report errors in the content of this documentation with the feedback links below.
Bug reports
Report bugs in the functionality of the described tool or API through Bug Reporter.
Formatting problems
Report formatting mistakes in the online version of these pages with the feedback links below.