bsd/man/man2/getpgrp.2

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  32 .\"     @(#)getpgrp.2   8.1 (Berkeley) 6/4/93
  33 .\" $FreeBSD: src/lib/libc/sys/getpgrp.2,v 1.11.2.6 2001/12/14 18:34:00 ru Exp $
  34 .\"
  35 .Dd June 4, 1993
  36 .Dt GETPGRP 2
  37 .Os
  38 .Sh NAME
  39 .Nm getpgid ,
  40 .Nm getpgrp
  41 .Nd get process group
  42 .Sh LIBRARY
  43 .Lb libc
  44 .Sh SYNOPSIS
  45 .In unistd.h
  46 .Ft pid_t
  47 .Fo getpgid
  48 .Fa "pid_t pid"
  49 .Fc
  50 .Ft pid_t
  51 .Fo getpgrp
  52 .Fa void
  53 .Fc
  54 .Sh DESCRIPTION
  55 The process group of the current process is returned by
  56 .Fn getpgrp .
  57 The process group of the process identified by
  58 .Fa pid
  59 is returned by
  60 .Fn getpgid .
  61 If
  62 .Fa pid
  63 is zero,
  64 .Fn getpgid
  65 returns the process group of the current process.
  66 .Pp
  67 Process groups are used for distribution of signals, and
  68 by terminals to arbitrate requests for their input: processes
  69 that have the same process group as the terminal are foreground
  70 and may read, while others will block with a signal if they attempt
  71 to read.
  72 .Pp
  73 This call is thus used by programs such as
  74 .Xr csh 1
  75 to create
  76 process groups
  77 in implementing job control.
  78 The
  79 .Fn tcgetpgrp
  80 and
  81 .Fn tcsetpgrp
  82 calls
  83 are used to get/set the process group of the control terminal.
  84 .Sh RETURN VALUES
  85 The
  86 .Fn getpgrp
  87 call always succeeds.
  88 Upon successful completion, the
  89 .Fn getpgid
  90 call returns the process group of the specified process;
  91 otherwise, it returns a value of \-1 and sets
  92 .Va errno
  93 to indicate the error.
  94 .Sh ERRORS
  95 .Fn getpgid
  96 will succeed unless:
  97 .Bl -tag -width Er
  98 .\" ==========
  99 .It Bq Er ESRCH
 100 There is no process whose process ID equals
 101 .Fa pid .
 102 .El
 103 .Sh SEE ALSO
 104 .Xr getsid 2 ,
 105 .Xr setpgid 2 ,
 106 .Xr termios 4
 107 .Sh HISTORY
 108 The
 109 .Fn getpgrp
 110 function call appeared in
 111 .Bx 4.0 .
 112 The
 113 .Fn getpgid
 114 function call is derived from its usage in System V Release 4.
 115 .Sh STANDARDS
 116 The
 117 .Fn getpgrp
 118 function call is expected to conform to
 119 .St -p1003.1-90 .
 120 .Sh COMPATIBILITY
 121 This version of
 122 .Fn getpgrp
 123 differs from past Berkeley versions by not taking a
 124 .Fa "pid_t pid"
 125 argument.
 126 This incompatibility is required by
 127 .St -p1003.1-90 .
 128 .Pp
 129 From the
 130 .St -p1003.1-90
 131 Rationale:
 132 .Pp
 133 .Bx 4.3
 134 provides a
 135 .Fn getpgrp
 136 function that returns the process group ID for a specified process.
 137 Although this function is used to support job control, all known
 138 job-control shells always specify the calling process with this
 139 function.
 140 Thus, the simpler
 141 .At V
 142 .Fn getpgrp
 143 suffices, and the added complexity of the
 144 .Bx 4.3
 145 .Fn getpgrp
 146 has been omitted from POSIX.1.
 147 The old functionality is available from the
 148 .Fn getpgid
 149 function.