1.\" 2.\" Copyright 2002 Massachusetts Institute of Technology 3.\" 4.\" Permission to use, copy, modify, and distribute this software and 5.\" its documentation for any purpose and without fee is hereby 6.\" granted, provided that both the above copyright notice and this 7.\" permission notice appear in all copies, that both the above 8.\" copyright notice and this permission notice appear in all 9.\" supporting documentation, and that the name of M.I.T. not be used 10.\" in advertising or publicity pertaining to distribution of the 11.\" software without specific, written prior permission. M.I.T. makes 12.\" no representations about the suitability of this software for any 13.\" purpose. It is provided "as is" without express or implied 14.\" warranty. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY M.I.T. ``AS IS''. M.I.T. DISCLAIMS 17.\" ALL EXPRESS OR IMPLIED WARRANTIES WITH REGARD TO THIS SOFTWARE, 18.\" INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 19.\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT 20.\" SHALL M.I.T. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 21.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 22.\" LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF 23.\" USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND 24.\" ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 25.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 26.\" OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27.\" SUCH DAMAGE. 28.\" 29.Dd July 2, 2022 30.Dt PSELECT 2 31.Os 32.Sh NAME 33.Nm pselect 34.Nd synchronous I/O multiplexing a la POSIX.1g 35.Sh LIBRARY 36.Lb libc 37.Sh SYNOPSIS 38.In sys/select.h 39.Ft int 40.Fo pselect 41.Fa "int nfds" 42.Fa "fd_set * restrict readfds" 43.Fa "fd_set * restrict writefds" 44.Fa "fd_set * restrict exceptfds" 45.Fa "const struct timespec * restrict timeout" 46.Fa "const sigset_t * restrict newsigmask" 47.Fc 48.Sh DESCRIPTION 49The 50.Fn pselect 51function was introduced by 52.St -p1003.1g-2000 53as a slightly stronger version of 54.Xr select 2 . 55The 56.Fa nfds , readfds , writefds , 57and 58.Fa exceptfds 59arguments are all identical to the analogous arguments of 60.Fn select . 61The 62.Fa timeout 63argument in 64.Fn pselect 65points to a 66.Vt "const struct timespec" 67rather than the potentially modifiable 68.Vt "struct timeval" 69used by 70.Fn select ; 71as in 72.Fn select , 73a null pointer may be passed to indicate that 74.Fn pselect 75should wait indefinitely. 76Finally, 77.Fa newsigmask 78specifies a signal mask which is set while waiting for input. 79When 80.Fn pselect 81returns, the original signal mask is restored. 82If 83.Fa newsigmask 84is a null pointer, 85.Fn pselect 86behaves like 87.Fn select 88with no setting or restoration of the signal mask. 89.Pp 90See 91.Xr select 2 92for a more detailed discussion of the semantics of this interface, and 93for macros used to manipulate the 94.Vt "fd_set" 95data type. 96.Sh RETURN VALUES 97The 98.Fn pselect 99function returns the same values and under the same conditions as 100.Fn select . 101.Sh ERRORS 102The 103.Fn pselect 104function may fail for any of the reasons documented for 105.Xr select 2 106and (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.Xr sigsuspend 2 114.Sh STANDARDS 115The 116.Fn pselect 117function conforms to 118.St -p1003.1-2001 . 119.Sh HISTORY 120The 121.Fn pselect 122function first appeared in 123.Fx 5.0 . 124.Sh AUTHORS 125The first implementation of 126.Fn pselect 127function and this manual page were written by 128.An Garrett Wollman Aq Mt wollman@FreeBSD.org . 129