kill(2)kill(2)NAMEkill - Send a signal to a process or to a group of processes
SYNOPSIS
#include <signal.h>
int kill(
pid_t process,
int signal );
Application developers may want to specify an #include statement for
<sys/types.h> before the one for <signal.h> if programs are being
developed for multiple platforms. The additional #include statement is
not required on Tru64 UNIX systems or by ISO or XSH specifications, but
may be on other vendors' systems that conform to these standards.
STANDARDS
Interfaces documented on this reference page conform to industry stan‐
dards as follows:
kill(): XSH4.0, XSH4.2, XSH5.0
Refer to the standards(5) reference page for more information about
industry standards and associated tags.
PARAMETERS
Specifies the process or group of processes. Specifies the signal. If
the signal parameter is a value of 0 (the null signal), error checking
is performed but no signal is sent. This can be used to check the
validity of the process parameter.
DESCRIPTION
The kill() function sends the signal specified by the signal parameter
to the process or group of processes specified by the process parame‐
ter.
To send a signal to another process, at least one of the following must
be true: The real or the saved set-user-ID of the sending process
matches the real or effective user ID of the receiving process. The
process is trying to send the SIGCONT signal to one of its session's
processes. The process has root privileges.
Processes can send signals to themselves.
Sending a signal does not imply that the operation is successful. All
signal operations must pass the access checks prescribed by each
enforced access control policy on the system.
If the process parameter is greater than 0 (zero), the signal specified
by the signal parameter is sent to the process that has a process ID
equal to the value of the process parameter.
If the process parameter is equal to 0 (zero), the signal specified by
the signal parameter is sent to all of the processes (other than system
processes) whose process group ID is equal to the process group ID of
the sender.
If the process parameter is equal to -1, the signal specified by the
signal parameter is sent to all of the processes other than system pro‐
cesses for which the process has permission to send that signal. For
example, if the effective user ID of the sender has root privileges,
the signal specified by the signal parameter is sent to all of the pro‐
cesses other than system processes.
If the process parameter is negative but not -1, the signal specified
by the signal parameter is sent to all of the processes that have a
process group ID equal to the absolute value of the process parameter.
[Tru64 UNIX] In a TruCluster Server cluster, if the process parameter
is greater than 0 (zero), the signal specified by the signal parameter
is sent to the process that has a process ID equal to the value of the
process parameter, even if that process is on another cluster member.
The process ID is guaranteed to be unique across the cluster.
[Tru64 UNIX] In a TruCluster Server cluster, if the process parameter
is equal to -1, the signal specified by the signal parameter is sent to
all non-system processes (on the current cluster member) for which the
process has permission to send that signal.
[Tru64 UNIX] In a TruCluster Server cluster, if the process parameter
is negative but not -1, the signal specified by the signal parameter is
sent to all of the processes that have a process group ID equal to the
absolute value of the process parameter, even if those processes are on
another cluster member.
NOTES
Some applications and scripts depend on the process ID of the init pro‐
gram being 1 (one): do not depend on it. Instead, use standard methods,
such as the ps and grep commands, to obtain all process IDs.
RETURN VALUES
Upon successful completion, the kill() function returns a value of 0
(zero). Otherwise, a value of -1 is returned and errno is set to indi‐
cate the error.
ERRORS
The kill() function sets errno to the specified values for the follow‐
ing conditions: The signal parameter is not a valid signal number.
[Tru64 UNIX] The signal parameter is SIGKILL, SIGSTOP, SIGTSTP
or SIGCONT and the process parameter is the process ID of the
init program. No process or process group can be found corre‐
sponding to that specified by the process parameter. The real
or saved user ID does not match the real or effective user ID of
the receiving process, the calling process does not have appro‐
priate privilege, and the process is not sending a SIGCONT sig‐
nal to one of its session's processes. [Tru64 UNIX] The call‐
ing process does not have appropriate privileges.
SEE ALSO
Functions: getpid(2), killpg(2), setpgid(2), sigaction(2), sigvec(2),
raise(3)
Standards: standards(5)kill(2)