From a9157ce950dfe2fc30795d43b9d79b9d1bffc48b Mon Sep 17 00:00:00 2001 From: Jacob McDonnell Date: Sat, 25 Apr 2026 19:54:44 -0400 Subject: docs: Added All OpenBSD Manuals --- static/openbsd/man2/select.2 | 248 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 248 insertions(+) create mode 100644 static/openbsd/man2/select.2 (limited to 'static/openbsd/man2/select.2') diff --git a/static/openbsd/man2/select.2 b/static/openbsd/man2/select.2 new file mode 100644 index 00000000..3dc9d35a --- /dev/null +++ b/static/openbsd/man2/select.2 @@ -0,0 +1,248 @@ +.\" $OpenBSD: select.2,v 1.45 2022/01/21 16:18:16 deraadt Exp $ +.\" $NetBSD: select.2,v 1.5 1995/06/27 22:32:28 cgd Exp $ +.\" +.\" Copyright (c) 1983, 1991, 1993 +.\" The Regents of the University of California. All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" 3. Neither the name of the University nor the names of its contributors +.\" may be used to endorse or promote products derived from this software +.\" without specific prior written permission. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" @(#)select.2 8.2 (Berkeley) 3/25/94 +.\" +.Dd $Mdocdate: January 21 2022 $ +.Dt SELECT 2 +.Os +.Sh NAME +.Nm select , +.Nm pselect , +.Nm FD_SET , +.Nm FD_CLR , +.Nm FD_ISSET , +.Nm FD_ZERO +.Nd synchronous I/O multiplexing +.Sh SYNOPSIS +.In sys/select.h +.Ft int +.Fn select "int nfds" "fd_set *readfds" "fd_set *writefds" "fd_set *exceptfds" "struct timeval *timeout" +.Ft int +.Fn pselect "int nfds" "fd_set *readfds" "fd_set *writefds" "fd_set *exceptfds" "const struct timespec *timeout" "const sigset_t *mask" +.Fn FD_SET fd &fdset +.Fn FD_CLR fd &fdset +.Fn FD_ISSET fd &fdset +.Fn FD_ZERO &fdset +.Sh DESCRIPTION +.Fn select +examines the I/O descriptor sets whose addresses are passed in +.Fa readfds , +.Fa writefds , +and +.Fa exceptfds +to see if some of their descriptors +are ready for reading, are ready for writing, or have an exceptional +condition pending, respectively. +Exceptional conditions include the presence of out-of-band data +on a socket. +The first +.Fa nfds +descriptors are checked in each set; +i.e., the descriptors from 0 through +.Fa nfds Ns -1 +in the descriptor sets are examined. +On return, +.Fn select +replaces the given descriptor sets +with subsets consisting of those descriptors that are ready +for the requested operation. +.Fn select +returns the total number of ready descriptors in all the sets. +.Pp +The descriptor sets are stored as bit fields in arrays of integers. +The following macros are provided for manipulating such descriptor sets: +.Fn FD_ZERO &fdset +initializes a descriptor set +.Fa fdset +to the null set. +.Fn FD_SET fd &fdset +includes a particular descriptor +.Fa fd +in +.Fa fdset . +.Fn FD_CLR fd &fdset +removes +.Fa fd +from +.Fa fdset . +.Fn FD_ISSET fd &fdset +is non-zero if +.Fa fd +is a member of +.Fa fdset , +zero otherwise. +The behavior of these macros is undefined if +a descriptor value is less than zero or greater than or equal to +.Dv FD_SETSIZE , +which is normally at least equal +to the maximum number of descriptors supported by the system. +.Pp +If +.Fa timeout +is a non-null pointer, it specifies a maximum interval to wait for the +selection to complete. +If +.Fa timeout +is a null pointer, the select blocks indefinitely. +To effect a poll, the +.Fa timeout +argument should be non-null, pointing to a zero-valued timeval structure. +.Fa timeout +is not changed by +.Fn select , +and may be reused on subsequent calls; however, it is good style to +re-initialize it before each invocation of +.Fn select . +.Pp +Any of +.Fa readfds , +.Fa writefds , +and +.Fa exceptfds +may be given as null pointers if no descriptors are of interest. +.Pp +The +.Fn pselect +function is similar to +.Fn select +except that it specifies the timeout using a timespec structure. +Also, if +.Fa mask +is a non-null pointer, +.Fn pselect +atomically sets the calling thread's signal mask to the signal set +pointed to by +.Fa mask +for the duration of the function call. +In this case, the original signal mask will be restored before +.Fn pselect +returns. +.Sh RETURN VALUES +If successful, +.Fn select +and +.Fn pselect +return the number of ready descriptors that are contained in +the descriptor sets. +If a descriptor is included in multiple descriptor sets, +each inclusion is counted separately. +If the time limit expires before any descriptors become ready, +they return 0. +.Pp +Otherwise, if +.Fn select +or +.Fn pselect +return with an error, including one due to an interrupted call, +they return \-1, +and the descriptor sets will be unmodified. +.Sh ERRORS +An error return from +.Fn select +or +.Fn pselect +indicates: +.Bl -tag -width Er +.It Bq Er EFAULT +One or more of +.Fa readfds , +.Fa writefds , +or +.Fa exceptfds +points outside the process's allocated address space. +.It Bq Er EBADF +One of the descriptor sets specified an invalid descriptor. +.It Bq Er EINTR +A signal was delivered before the time limit expired and +before any of the selected descriptors became ready. +.It Bq Er EINVAL +The specified time limit is invalid. +One of its components is negative or too large. +.It Bq Er EINVAL +.Fa nfds +was less than 0. +.El +.Sh SEE ALSO +.Xr accept 2 , +.Xr clock_gettime 2 , +.Xr connect 2 , +.Xr gettimeofday 2 , +.Xr poll 2 , +.Xr read 2 , +.Xr recv 2 , +.Xr send 2 , +.Xr write 2 , +.Xr getdtablesize 3 +.Sh STANDARDS +The +.Fn select +and +.Fn pselect +functions conform to +.St -p1003.1-2008 . +.Sh HISTORY +The +.Fn select +system call first appeared in +.Bx 4.1c . +The +.Fn pselect +system call has been available since +.Ox 5.4 . +.Sh BUGS +Although the provision of +.Xr getdtablesize 3 +was intended to allow user programs to be written independent +of the kernel limit on the number of open files, the dimension +of a sufficiently large bit field for select remains a problem. +If descriptor values greater than FD_SETSIZE are possible in +a program, use +.Xr poll 2 +instead. +.Pp +.Fn select +should probably have been designed to return the time remaining from the +original timeout, if any, by modifying the time value in place. +Even though some systems stupidly act in this different way, it is +unlikely this semantic will ever be commonly implemented, as the +change causes massive source code compatibility problems. +Furthermore, recent new standards have dictated the current behaviour. +In general, due to the existence of those brain-damaged +non-conforming systems, it is unwise to assume that the timeout +value will be unmodified by the +.Fn select +call, and the caller should reinitialize it on each invocation. +Calculating the delta is easily done by calling +.Xr gettimeofday 2 +before and after the call to +.Fn select , +and using +.Xr timersub 3 . -- cgit v1.2.3