gen/pselect.3

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  31 .Dd June 16, 2002
  32 .Dt PSELECT 3
  33 .Os
  34 .Sh NAME
  35 .Nm pselect
  36 .Nd synchronous I/O multiplexing a la POSIX.1g
  37 .Sh LIBRARY
  38 .Lb libc
  39 .Sh SYNOPSIS
  40 .In unistd.h
  41 .Ft int
  42 .Fo pselect
  43 .Fa "int nfds"
  44 .Fa "fd_set *restrict readfds"
  45 .Fa "fd_set *restrict writefds"
  46 .Fa "fd_set *restrict errorfds"
  47 .Fa "const struct timespec *restrict timeout"
  48 .Fa "const sigset_t *restrict sigmask"
  49 .Fc
  50 .Sh DESCRIPTION
  51 The
  52 .Fn pselect
  53 function was introduced by
  54 .St -p1003.1g-2000
  55 as a slightly stronger version of
  56 .Xr select 2 .
  57 The
  58 .Fa nfds , readfds , writefds ,
  59 and
  60 .Fa errorfds
  61 arguments are all identical to the analogous arguments of
  62 .Fn select .
  63 The
  64 .Fa timeout
  65 argument in
  66 .Fn pselect
  67 points to a
  68 .Vt "const struct timespec" ,
  69 rather than the (modifiable)
  70 .Vt "struct timeval"
  71 used by
  72 .Fn select ;
  73 as in
  74 .Fn select ,
  75 a null pointer may be passed to indicate that
  76 .Fn pselect
  77 should wait indefinitely.
  78 Finally,
  79 .Fa sigmask
  80 specifies a signal mask which is set while waiting for input.
  81 When
  82 .Fn pselect
  83 returns, the original signal mask is restored.
  84 .Pp
  85 See
  86 .Xr select 2
  87 for a more detailed discussion of the semantics of this interface, and
  88 for macros used to manipulate the
  89 .Vt "fd_set"
  90 data type.
  91 .Sh IMPLEMENTATION NOTES
  92 The
  93 .Fn pselect
  94 function is implemented in the C library as a wrapper around
  95 .Fn select .
  96 .Sh RETURN VALUES
  97 The
  98 .Fn pselect
  99 function returns the same values and under the same conditions as
 100 .Fn select .
 101 .Sh ERRORS
 102 The
 103 .Fn pselect
 104 function may fail for any of the reasons documented for
 105 .Xr select 2
 106 and (if a signal mask is provided)
 107 .Xr sigprocmask 2 .
 108 .Sh SEE ALSO
 109 .Xr kqueue 2 ,
 110 .Xr poll 2 ,
 111 .Xr select 2 ,
 112 .Xr sigprocmask 2
 113 .Sh STANDARDS
 114 The
 115 .Fn pselect
 116 function conforms to
 117 .St -p1003.1-2001 .
 118 .Sh HISTORY
 119 The
 120 .Fn pselect
 121 function first appeared in
 122 .Fx 5.0 .
 123 .Sh AUTHORS
 124 The
 125 .Fn pselect
 126 function and this manual page were written by
 127 .An Garrett Wollman Aq wollman@FreeBSD.org .