bsd/man/man2/kill.2

   1 .\"     $NetBSD: kill.2,v 1.7 1995/02/27 12:33:53 cgd Exp $
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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 .Fo kill
  46 .Fa "pid_t pid"
  47 .Fa "int sig"
  48 .Fc
  49 .Sh DESCRIPTION
  50 The
  51 .Fn kill
  52 function sends the signal specified by
  53 .Fa sig
  54 to
  55 .Fa pid ,
  56 a
  57 process or a group of processes.
  58 Typically,
  59 .Fa Sig
  60 will be one of the signals specified in
  61 .Xr sigaction 2 .
  62 A value of 0, however,
  63 will cause error checking to be performed (with no signal being sent).
  64 This can be used to check the validity of
  65 .Fa pid .
  66 .Pp
  67 For a process to have permission to send a signal to a process designated
  68 by
  69 .Fa pid ,
  70 the real or effective user ID of the receiving process must match
  71 that of the sending process or the user must have appropriate privileges
  72 (such as given by a set-user-ID program or the user is the super-user).
  73 A single exception is the signal SIGCONT,
  74 which may always be sent to any descendant of the current process.
  75 .Bl -tag -width Ds
  76 .It \&If Fa pid No \&is greater than zero :
  77 .Fa Sig
  78 is sent to the process whose ID is equal to
  79 .Fa pid.
  80 .It \&If Fa pid No \&is zero :
  81 .Fa Sig
  82 is sent to all processes whose group ID is equal
  83 to the process group ID of the sender,
  84 and for which the process has permission;
  85 this is a variant of
  86 .Xr killpg 2 .
  87 .It \&If Fa pid No \&is -1 :
  88 If the user has super-user privileges,
  89 the signal is sent to all processes excluding
  90 system processes and the process sending the signal.
  91 If the user is not the super user,
  92 the signal is sent to all processes with the same uid as the user,
  93 excluding the process sending the signal.
  94 No error is returned if any process could be signaled.
  95 .El
  96 .Pp
  97 For compatibility with System V,
  98 if the process number is negative but not -1,
  99 the signal is sent to all processes whose process group ID
 100 is equal to the absolute value of the process number.
 101 This is a variant of
 102 .Xr killpg 2 .
 103 .Sh RETURN VALUES
 104 Upon successful completion, a value of 0 is returned.
 105 Otherwise, a value of -1 is returned and
 106 .Va errno
 107 is set to indicate the error.
 108 .Sh ERRORS
 109 .Fn Kill
 110 will fail and no signal will be sent if:
 111 .Bl -tag -width Er
 112 .\" ==========
 113 .It Bq Er EINVAL
 114 .Fa Sig
 115 is not a valid, supported signal number.
 116 .\" ==========
 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 .\" ==========
 123 .It Bq Er ESRCH
 124 No process or process group can be found
 125 corresponding to that specified by
 126 .Fa pid .
 127 .\" ==========
 128 .It Bq Er ESRCH
 129 The process id was given as 0,
 130 but the sending process does not have a process group.
 131 .El
 132 .Sh SEE ALSO
 133 .Xr getpgrp 2 ,
 134 .Xr getpid 2 ,
 135 .Xr killpg 2 ,
 136 .Xr sigaction 2
 137 .Sh STANDARDS
 138 The
 139 .Fn kill
 140 function is expected to conform to
 141 .St -p1003.1-88 .