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2.\" Copyright 2002 Massachusetts Institute of Technology
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29.\" $FreeBSD: src/lib/libc/gen/pselect.3,v 1.4 2002/12/18 10:13:54 ru Exp $
30.\"
31.Dd June 16, 2002
32.Dt PSELECT 2
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 sys/select.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
51The
52.Fn pselect
53function was introduced by
54.St -p1003.1g-2000
55as a slightly stronger version of
56.Xr select 2 .
57The
58.Fa nfds , readfds , writefds ,
59and
60.Fa errorfds
61arguments are all identical to the analogous arguments of
62.Fn select .
63The
64.Fa timeout
65argument in
66.Fn pselect
67points to a
68.Vt "const struct timespec" ,
69rather than the (modifiable)
70.Vt "struct timeval"
71used by
72.Fn select ;
73as in
74.Fn select ,
75a null pointer may be passed to indicate that
76.Fn pselect
77should wait indefinitely.
78Finally,
79.Fa sigmask
80specifies a signal mask which is set while waiting for input.
81When
82.Fn pselect
83returns, the original signal mask is restored.
84.Pp
85See
86.Xr select 2
87for a more detailed discussion of the semantics of this interface, and
88for macros used to manipulate the
89.Vt "fd_set"
90data type.
91.Sh RETURN VALUES
92The
93.Fn pselect
94function returns the same values and under the same conditions as
95.Fn select .
96.Sh ERRORS
97The
98.Fn pselect
99function may fail for any of the reasons documented for
100.Xr select 2
101and (if a signal mask is provided)
102.Xr sigprocmask 2 .
103.Sh SEE ALSO
104.Xr kqueue 2 ,
105.Xr poll 2 ,
106.Xr select 2 ,
107.Xr sigprocmask 2
108.Sh STANDARDS
109The
110.Fn pselect
111function conforms to
112.St -p1003.1-2001 .
113.Sh HISTORY
114The
115.Fn pselect
116function first appeared in
117.Fx 5.0 .
118.Sh AUTHORS
119The
120.Fn pselect
121manual page was written by
122.An Garrett Wollman Aq wollman@FreeBSD.org .