kill(1) General Commands Manual kill(1)
NAME
kill - send a signal to a process; terminate a process
SYNOPSIS
signame] pid ...
signum] pid ...
Obsolescent Versions:
DESCRIPTION
The command sends a signal to each process specified by a pid process identifier. The default signal is which normally terminates pro-
cesses that do not trap or ignore the signal.
Options
recognizes the following options:
List all values of
signame supported by the implementation. No signals are sent with this option. The symbolic names of the signals
(without the prefix) are written to standard output, separated by spaces and newlines.
Send the specified signal name.
The default is number signame can be specified in upper- and/or lowercase, with or without the prefix. These val-
ues can be obtained by using the option. The symbolic name represents signal value zero. See "Signal Names and
Numbers" below.
Send the specified decimal signal number.
The default is See "Signal Names and Numbers" below.
(Obsolescent.) Equivalent to
(Obsolescent.) Equivalent to
Operands
pid is a process identifier, an unsigned or negative integer that can be one of the following:
The number of a process.
All processes, except special system processes, whose process group
ID is equal to the process group ID of the sender.
All processes, except special system processes,
if the user has appropriate privileges. Otherwise, all processes, except special system processes, whose real or effective
user ID is the same as the user ID of the sending process.
All processes, except special system processes, whose process group
ID is equal to the absolute value of pid and whose real or effective user ID is the same as the user of the sending process.
Process numbers can be found with the command (see ps(1)) and with the built-in command available in some shells.
Signal Names and Numbers
The following table describes a few of the more common signals that can be useful from a terminal. For a complete list and a full descrip-
tion, see the header file and the manual entry signal(5).
signum signame Name Description
----------------------------------------------------------------------------
0 SIGNULL Null Check access to pid
1 SIGHUP Hangup Terminate; can be trapped
2 SIGINT Interrupt Terminate; can be trapped
3 SIGQUIT Quit Terminate with core dump; can be trapped
9 SIGKILL Kill Forced termination; cannot be trapped
15 SIGTERM Terminate Terminate; can be trapped
24 SIGSTOP Stop Pause the process; cannot be trapped
25 SIGTSTP Terminal stop Pause the process; can be trapped
26 SIGCONT Continue Run a stopped process
the null signal, invokes error checking but no signal is actually sent. This can be used to test the validity or existence of pid.
the (default) terminate signal, can be trapped by the receiving process, allowing the receiver to execute an orderly shutdown or to ignore
the signal entirely. For orderly operations, this is the preferred choice.
the kill signal, forces a process to terminate immediately. Since cannot be trapped or ignored, it is useful for terminating a process
that does not respond to
The receiving process must belong to the user of the sending process, unless the user has appropriate privileges.
As a single special case, the continue signal SIGCONT can be sent to any process that is a member of the same session as the sending
process.
RETURN VALUE
Upon completion, returns with one of the following values:
At least one matching process was found for each
pid operand, and the specified signal was successfully processed for at least one matching process.
An error occurred.
EXAMPLES
The command:
signals process number 6135 to terminate. This gives the process an opportunity to exit gracefully (removing temporary files, etc.).
The following equivalent commands:
terminate process number 6135 abruptly by sending a signal to the process. This tells the kernel to remove the process immediately.
WARNINGS
If a process hangs during some operation (such as I/O) so that it is never scheduled, it cannot die until it is allowed to run. Thus, such
a process may never go away after the kill. Similarly, defunct processes (see ps(1)) may have already finished executing, but remain on
the system until their parent reaps them (see wait(2)). Using to send signals to them has no effect.
Some non-HP-UX implementations provide only as a shell built-in command.
DEPENDENCIES
This manual entry describes the external command and the built-in command of the POSIX shell (see sh-posix(1)). Other shells, such as C
and Korn (see csh(1) and ksh(1) respectively), also provide as a built-in command. The syntax for and output from these built-ins may be
different.
SEE ALSO
csh(1), ksh(1), ps(1), sh(1), sh-posix(1), kill(2), wait(2), signal(5).
STANDARDS CONFORMANCE
kill(1)