man/pthread_atfork.3

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  36 .Dd June 21, 2004
  37 .Dt PTHREAD_ATFORK 3
  38 .Os
  39 .Sh NAME
  40 .Nm pthread_atfork
  41 .Nd register handlers to be called before and after
  42 .Fn fork
  43 .Sh SYNOPSIS
  44 .In pthread.h
  45 .Ft int
  46 .Fo pthread_atfork
  47 .Fa "void \*[lp]*prepare\*[rp]\*[lp]void\*[rp]"
  48 .Fa "void \*[lp]*parent\*[rp]\*[lp]void\*[rp]"
  49 .Fa "void \*[lp]*child\*[rp]\*[lp]void\*[rp]"
  50 .Fc
  51 .Sh DESCRIPTION
  52 The
  53 .Fn pthread_atfork
  54 function declares fork handlers to be called before and after
  55 .Xr fork 2 ,
  56 in the context of the thread that called
  57 .Xr fork 2 .
  58 .Pp
  59 The handlers registered with
  60 .Fn pthread_atfork
  61 are called at the moments in time described below:
  62 .Bl -tag -width ".Fa prepare"
  63 .It Fa prepare
  64 Before
  65 .Xr fork 2
  66 processing commences in the parent process.
  67 If more than one
  68 .Fa prepare
  69 handler is registered they will be called in the opposite order
  70 they were registered.
  71 .It Fa parent
  72 After
  73 .Xr fork 2
  74 completes in the parent process.
  75 If more than one
  76 .Fa parent
  77 handler is registered they will be called in the same order
  78 they were registered.
  79 .It Fa child
  80 After
  81 .Xr fork 2
  82 processing completes in the child process.
  83 If more than one
  84 .Fa child
  85 handler is registered they will be called in the same order
  86 they were registered.
  87 .El
  88 .Pp
  89 If no handling is desired at one or more of these three points,
  90 a null pointer may be passed as the corresponding fork handler.
  91 .Pp
  92 .Em Important :
  93 only async-signal-safe functions are allowed on the child side of
  94 .Fn fork .
  95 See
  96 .Xr sigaction 2
  97 for details.
  98 .Sh RETURN VALUES
  99 If successful, the
 100 .Fn pthread_atfork
 101 function will return zero.
 102 Otherwise an error number will be returned to indicate the error.
 103 .Sh ERRORS
 104 The
 105 .Fn pthread_atfork
 106 function will fail if:
 107 .Bl -tag -width Er
 108 .It Bq Er ENOMEM
 109 The system lacked the necessary resources to add another handler to the list.
 110 .El
 111 .Sh SEE ALSO
 112 .Xr fork 2 ,
 113 .Xr pthread 3
 114 .Sh STANDARDS
 115 The
 116 .Fn pthread_atfork
 117 conforms to
 118 .St -p1003.1-96 .