1KILL(2) Linux Programmer's Manual KILL(2)
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6 kill - send signal to a process
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9 #include <sys/types.h>
10 #include <signal.h>
11 int kill(pid_t pid, int sig);
13 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
15 kill(): _POSIX_C_SOURCE
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19 The kill() system call can be used to send any signal to any process
20 group or process.
21 If pid is positive, then signal sig is sent to the process with the ID
23 specified by pid.
24 If pid equals 0, then sig is sent to every process in the process group
26 of the calling process.
27 If pid equals -1, then sig is sent to every process for which the call‐
29 ing process has permission to send signals, except for process 1
30 (init), but see below.
31 If pid is less than -1, then sig is sent to every process in the
33 process group whose ID is -pid.
34 If sig is 0, then no signal is sent, but existence and permission
36 checks are still performed; this can be used to check for the existence
37 of a process ID or process group ID that the caller is permitted to
38 signal.
39 For a process to have permission to send a signal, it must either be
41 privileged (under Linux: have the CAP_KILL capability in the user name‐
42 space of the target process), or the real or effective user ID of the
43 sending process must equal the real or saved set-user-ID of the target
44 process. In the case of SIGCONT, it suffices when the sending and re‐
45 ceiving processes belong to the same session. (Historically, the rules
46 were different; see NOTES.)
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49 On success (at least one signal was sent), zero is returned. On error,
50 -1 is returned, and errno is set appropriately.
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53 EINVAL An invalid signal was specified.
54 EPERM The calling process does not have permission to send the signal
56 to any of the target processes.
57 ESRCH The target process or process group does not exist. Note that
59 an existing process might be a zombie, a process that has termi‐
60 nated execution, but has not yet been wait(2)ed for.
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63 POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.
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66 The only signals that can be sent to process ID 1, the init process,
67 are those for which init has explicitly installed signal handlers.
68 This is done to assure the system is not brought down accidentally.
69 POSIX.1 requires that kill(-1,sig) send sig to all processes that the
71 calling process may send signals to, except possibly for some implemen‐
72 tation-defined system processes. Linux allows a process to signal it‐
73 self, but on Linux the call kill(-1,sig) does not signal the calling
74 process.
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