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28 .\" @(#)kill.2 8.3 (Berkeley) 4/19/94
35 .Nd send signal to a process
42 .Fn kill "pid_t pid" "int sig"
46 system call sends the signal given by
51 process or a group of processes.
55 may be one of the signals specified in
57 or it may be 0, in which case
58 error checking is performed but no
59 signal is actually sent.
60 This can be used to check the validity of
63 For a process to have permission to send a signal to a process designated
66 the user must be the super-user, or
67 the real or saved user ID of the receiving process must match
68 the real or effective user ID of the sending process.
69 A single exception is the signal SIGCONT, which may always be sent
70 to any process with the same session ID as the sender.
72 .Va security.bsd.conservative_signals
74 is set to 1, the user is not a super-user, and
75 the receiver is set-uid, then
76 only job control and terminal control signals may
77 be sent (in particular, only SIGKILL, SIGINT, SIGTERM, SIGALRM,
78 SIGSTOP, SIGTTIN, SIGTTOU, SIGTSTP, SIGHUP, SIGUSR1, SIGUSR2).
80 .It \&If Fa pid No \&is greater than zero :
84 is sent to the process whose ID is equal to
86 .It \&If Fa pid No \&is zero :
90 is sent to all processes whose group ID is equal
91 to the process group ID of the sender, and for which the
92 process has permission;
95 .It \&If Fa pid No \&is -1 :
96 If the user has super-user privileges,
97 the signal is sent to all processes excluding
105 and the process sending the signal.
106 If the user is not the super user, the signal is sent to all processes
107 which the caller has permissions to, excluding the process sending the signal.
108 No error is returned if any process could be signaled.
111 If the process number is negative but not -1,
112 the signal is sent to all processes whose process group ID
113 is equal to the absolute value of the process number.
122 will fail and no signal will be sent if:
128 is not a valid signal number.
130 No process or process group can be found corresponding to that specified by
133 The sending process does not have permission to send
135 to any receiving process.
148 system call is expected to conform to
155 The signal number was added to the