kill(2) System Calls Manual kill(2)
NAME
kill(), raise() - send a signal to a process or a group of processes
SYNOPSIS
DESCRIPTION
The system call sends a signal to a process or a group of processes, as specified by pid. The signal to be sent is specified by sig and is
either one from the list given in or
The system call sends a signal to the executing process or thread. The signal to be sent is specified by sig and is either one from the
list given in or In a single-threaded process the effect of the function is equivalent to calling
When used in a multithreaded program, the function sends the signal specified by sig to the executing thread. The effect of the function
is equivalent to calling
If sig is (the null signal), error checking is performed but no signal is actually sent. This can be used to check the validity of pid.
The real or effective user ID of the sending process must match the real or saved user ID of the receiving process unless the sending
process has appropriate privileges.
As a single special case, the continue signal can be sent to any process that is a member of the same session as the sending process.
The value is defined in the file and is guaranteed not to be the ID of any process in the system or the negation of the ID of any process
in the system.
If pid is greater than zero and not equal to sig is sent to the process whose process ID is equal to pid. pid can equal unless sig is or
If pid is sig is sent to all processes excluding special system processes whose process group ID is equal to the process group ID of the
sender.
If pid is and the sending process does not have the appropriate privileges, sig is sent to all processes excluding special system processes
whose real or saved user ID is equal to the real or effective user ID of the sender.
If pid is and the effective user ID of the sender is a user who has appropriate privileges, sig is sent to all processes excluding special
system processes.
If pid is behaves much as when pid is equal to except that sig is not sent to the calling process.
If pid is negative but not or sig is sent to all processes (excluding special system processes) whose process group ID is equal to the
absolute value of pid, and whose real and/or effective user ID meets the constraints described above for matching user IDs.
Security Restrictions
Some or all of the actions associated with this system call are subject to compartmental restrictions. See compartments(5) for more infor-
mation about compartmentalization on systems that support that feature. Compartmental restrictions can be overridden if the process pos-
sesses the privilege (COMMALLOWED). Processes owned by the superuser may not have this privilege. Processes owned by any user may have
this privilege, depending on system configuration.
Some or all of the actions associated with this system call require the (OWNER) and/or the (REBOOT) privileges. Processes owned by the
superuser will have these privileges. Processes owned by other users may have privilege(s), depending on system configuration. See privi-
leges(5) for more information about privileged access on systems that support fine-grained privileges.
RETURN VALUE
Upon successful completion, a value of is returned. Otherwise, a value of is returned and is set to indicate the error.
ERRORS
If fails, no signal is sent. is set to one of the following values.
sig is neither a valid signal number nor zero.
sig is or and pid is that of the initialization process (also known as
The user ID of the sending process is not a user who has
appropriate privileges and its real or effective user ID does not match the real or saved user ID of the receiving
process.
The sending and receiving processes are not in the same session and
the real or effective user ID does not match the real or saved user ID of the receiving process.
No process or process group can be found corresponding to that specified by
pid.
If fails, no signal is sent. is set to the following value.
sig is neither a valid signal number nor zero.
APPLICATION USAGE
Threads Considerations
can be used to post signals to another process but cannot be used to post signals to a specific thread in another process. For information
on posting signals to specific threads within the same process, see pthread_kill(3T).
LWP (Lightweight Processes) Considerations
Signals cannot be posted to specific LWPs in another process.
AUTHOR
was developed by HP, AT&T, and the University of California, Berkeley.
SEE ALSO
kill(1), getpid(2), setsid(2), signal(2), sigqueue(2), pthread_kill(3T).
STANDARDS CONFORMANCE
kill(2)