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28 .\" @(#)kill.2 8.3 (Berkeley) 4/19/94
36 .Nd send signal to a process
43 .Fn kill "pid_t pid" "int sig"
47 system call sends the signal given by
52 process or a group of processes.
56 may be one of the signals specified in
58 or it may be 0, in which case
59 error checking is performed but no
60 signal is actually sent.
61 This can be used to check the validity of
64 For a process to have permission to send a signal to a process designated
67 the user must be the super-user, or
68 the real or saved user ID of the receiving process must match
69 the real or effective user ID of the sending process.
70 A single exception is the signal SIGCONT, which may always be sent
71 to any process with the same session ID as the sender.
73 .Va security.bsd.conservative_signals
75 is set to 1, the user is not a super-user, and
76 the receiver is set-uid, then
77 only job control and terminal control signals may
78 be sent (in particular, only SIGKILL, SIGINT, SIGTERM, SIGALRM,
79 SIGSTOP, SIGTTIN, SIGTTOU, SIGTSTP, SIGHUP, SIGUSR1, SIGUSR2).
81 .It \&If Fa pid No \&is greater than zero :
85 is sent to the process whose ID is equal to
87 .It \&If Fa pid No \&is zero :
91 is sent to all processes whose group ID is equal
92 to the process group ID of the sender, and for which the
93 process has permission;
96 .It \&If Fa pid No \&is -1 :
97 If the user has super-user privileges,
98 the signal is sent to all processes excluding
106 and the process sending the signal.
107 If the user is not the super user, the signal is sent to all processes
108 with the same uid as the user excluding the process sending the signal.
109 No error is returned if any process could be signaled.
112 For compatibility with System V,
113 if the process number is negative but not -1,
114 the signal is sent to all processes whose process group ID
115 is equal to the absolute value of the process number.
124 will fail and no signal will be sent if:
130 is not a valid signal number.
132 No process or process group can be found corresponding to that specified by
135 The sending process does not have permission to send
137 to the receiving process.
150 system call is expected to conform to