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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 real or effective user ID of the receiving process must match
68 that of the sending process or the user must have appropriate privileges
69 (such as given by a set-user-ID program or the user is the super-user).
70 A single exception is the signal SIGCONT, which may always be sent
71 to any process with the same session ID as the caller.
73 .It \&If Fa pid No \&is greater than zero :
77 is sent to the process whose ID is equal to
79 .It \&If Fa pid No \&is zero :
83 is sent to all processes whose group ID is equal
84 to the process group ID of the sender, and for which the
85 process has permission;
88 .It \&If Fa pid No \&is -1 :
89 If the user has super-user privileges,
90 the signal is sent to all processes excluding
98 and the process sending the signal.
99 If the user is not the super user, the signal is sent to all processes
100 with the same uid as the user excluding the process sending the signal.
101 No error is returned if any process could be signaled.
104 For compatibility with System V,
105 if the process number is negative but not -1,
106 the signal is sent to all processes whose process group ID
107 is equal to the absolute value of the process number.
116 will fail and no signal will be sent if:
122 is not a valid signal number.
124 No process can be found corresponding to that specified by
127 The process id was given as 0
128 but the sending process does not have a process group.
130 The sending process is not the super-user and its effective
131 user id does not match the effective user-id of the receiving process.
132 When signaling a process group, this error is returned if any members
133 of the group could not be signaled.
145 system call is expected to conform to