bsd/man/man2/kill.2

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  34 .\"     @(#)kill.2      8.3 (Berkeley) 4/19/94
  35 .\"
  36 .Dd April 19, 1994
  37 .Dt KILL 2
  38 .Os BSD 4
  39 .Sh NAME
  40 .Nm kill
  41 .Nd send signal to a process
  42 .Sh SYNOPSIS
  43 .Fd #include <signal.h>
  44 .Ft int
  45 .Fn kill "pid_t pid" "int sig"
  46 .Sh DESCRIPTION
  47 The
  48 .Fn kill
  49 function sends the signal given by
  50 .Fa sig
  51 to
  52 .Fa pid ,
  53 a
  54 process or a group of processes.
  55 .Fa Sig
  56 may be one of the signals specified in
  57 .Xr sigaction 2
  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
  62 .Fa pid .
  63 .Pp
  64 For a process to have permission to send a signal to a process designated
  65 by
  66 .Fa pid ,
  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 descendant of the current process.
  72 .Bl -tag -width Ds
  73 .It \&If Fa pid No \&is greater than zero :
  74 .Fa Sig
  75 is sent to the process whose ID is equal to
  76 .Fa pid.
  77 .It \&If Fa pid No \&is zero :
  78 .Fa Sig
  79 is sent to all processes whose group ID is equal
  80 to the process group ID of the sender, and for which the
  81 process has permission;
  82 this is a variant of
  83 .Xr killpg 2 .
  84 .It \&If Fa pid No \&is -1 :
  85 If the user has super-user privileges,
  86 the signal is sent to all processes excluding
  87 system processes and the process sending the signal.
  88 If the user is not the super user, the signal is sent to all processes
  89 with the same uid as the user excluding the process sending the signal.
  90 No error is returned if any process could be signaled.
  91 .El
  92 .Pp
  93 For compatibility with System V,
  94 if the process number is negative but not -1,
  95 the signal is sent to all processes whose process group ID
  96 is equal to the absolute value of the process number.
  97 This is a variant of
  98 .Xr killpg 2 .
  99 .Sh RETURN VALUES
 100 Upon successful completion, a value of 0 is returned.
 101 Otherwise, a value of -1 is returned and
 102 .Va errno
 103 is set to indicate the error.
 104 .Sh ERRORS
 105 .Fn Kill
 106 will fail and no signal will be sent if:
 107 .Bl -tag -width Er
 108 .It Bq Er EINVAL
 109 .Fa Sig
 110 is not a valid signal number.
 111 .It Bq Er ESRCH
 112 No process can be found corresponding to that specified by
 113 .Fa pid .
 114 .It Bq Er ESRCH
 115 The process id was given as 0
 116 but the sending process does not have a process group.
 117 .It Bq Er EPERM
 118 The sending process is not the super-user and its effective
 119 user id does not match the effective user-id of the receiving process.
 120 When signaling a process group, this error is returned if any members
 121 of the group could not be signaled.
 122 .El
 123 .Sh SEE ALSO
 124 .Xr getpid 2 ,
 125 .Xr getpgrp 2 ,
 126 .Xr killpg 2 ,
 127 .Xr sigaction 2
 128 .Sh STANDARDS
 129 The
 130 .Fn kill
 131 function is expected to conform to
 132 .St -p1003.1-88 .