date and time created 91/04/12 13:40:31 by bostic

[unix-history] / usr / src / lib / libc / sys / select.2

diff --git a/usr/src/lib/libc/sys/select.2 b/usr/src/lib/libc/sys/select.2
index a24ce3e..12462a6 100644 (file)
--- a/usr/src/lib/libc/sys/select.2
+++ b/usr/src/lib/libc/sys/select.2
@@ -1,146 +1,156 @@
-.\" Copyright (c) 1983 Regents of the University of California.
-.\" All rights reserved.  The Berkeley software License Agreement
-.\" specifies the terms and conditions for redistribution.
+.\" Copyright (c) 1983, 1991 The Regents of the University of California.
+.\" All rights reserved.

 .\"
 .\"

-.\"    @(#)select.2    6.4 (Berkeley) %G%
+.\" %sccs.include.redist.man%

 .\"
 .\"

-.TH SELECT 2 ""
-.UC 5
-.SH NAME
-select \- synchronous I/O multiplexing
-.SH SYNOPSIS
-.nf
-.ft B
-#include <sys/types.h>
-#include <sys/time.h>
-.PP
-.ft B
-nfound = select(nfds, readfds, writefds, exceptfds, timeout)
-int nfound, nfds;
-fd_set *readfds, *writefds, *exceptfds;
-struct timeval *timeout;
-.PP
-.ft B
-FD_SET(fd, &fdset)     
-FD_CLR(fd, &fdset)     
-FD_ISSET(fd, &fdset)   
-FD_ZERO(&fdset)        
-int fd;
-fd_set fdset;
-.fi
-.SH DESCRIPTION
-.I Select
+.\"     @(#)select.2   6.8 (Berkeley) %G%
+.\"
+.Dd 
+.Dt SELECT 2
+.Os BSD 4.2
+.Sh NAME
+.Nm select
+.Nd synchronous I/O multiplexing
+.Sh SYNOPSIS
+.Fd #include <unistd.h>
+.Fd #include <sys/types.h>
+.Fd #include <sys/time.h>
+.Ft int
+.Fn select "int nfds" "fd_set *readfds" "fd_set *writefds" "fd_set *exceptfds" "struct timeval *timeout"
+.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
 examines the I/O descriptor sets whose addresses are passed in

-.IR readfds ,
-.IR writefds ,
+.Fa readfds ,
+.Fa writefds ,

 and
 and

-.I exceptfds
+.Fa exceptfds

 to see if some of their descriptors
 are ready for reading, are ready for writing, or have an exceptional
 condition pending, respectively.
 The first
 to see if some of their descriptors
 are ready for reading, are ready for writing, or have an exceptional
 condition pending, respectively.
 The first

-.I nfds
+.Fa nfds

 descriptors are checked in each set;
 descriptors are checked in each set;

-i.e. the descriptors from 0 through
-.IR nfds -1
+i.e., the descriptors from 0 through
+.Fa nfds Ns No -1

 in the descriptor sets are examined.
 On return,
 in the descriptor sets are examined.
 On return,

-.I select
+.Fn select

 replaces the given descriptor sets
 with subsets consisting of those descriptors that are ready
 for the requested operation.
 replaces the given descriptor sets
 with subsets consisting of those descriptors that are ready
 for the requested operation.

-The total number of ready descriptors in all the sets is returned in
-.IR nfound .
-.PP
+.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:
 The descriptor sets are stored as bit fields in arrays of integers.
 The following macros are provided for manipulating such descriptor sets:

-.I "FD_ZERO(&fdset)"
+.Fn FD_ZERO &fdsetx

 initializes a descriptor set
 initializes a descriptor set

-.I fdset
+.Fa fdset

 to the null set.
 to the null set.

-.I "FD_SET(fd, &fdset)"
+.Fn FD_SET fd &fdset

 includes a particular descriptor
 includes a particular descriptor

-.I fd
+.Fa fd

 in
 in

-.IR fdset .
-.I "FD_CLR(fd, &fdset)"
+.Fa fdset .
+.Fn FD_CLR fd &fdset

 removes
 removes

-.I fd
+.Fa fd

 from
 from

-.IR fdset .
-.I "FD_ISSET(fd, &fdset)"
-is nonzero if
-.I fd
+.Fa fdset .
+.Fn FD_ISSET fd &fdset
+is non-zero if
+.Fa fd

 is a member of
 is a member of

-.IR fdset ,
+.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
 zero otherwise.
 The behavior of these macros is undefined if
 a descriptor value is less than zero or greater than or equal to

-.IR FD_SETSIZE ,
+.Dv FD_SETSIZE ,

 which is normally at least equal
 to the maximum number of descriptors supported by the system.
 which is normally at least equal
 to the maximum number of descriptors supported by the system.

-.PP
+.Pp

 If
 If

-.I timeout
-is a non-zero pointer, it specifies a maximum interval to wait for the
+.Fa timeout
+is a non-nil pointer, it specifies a maximum interval to wait for the

 selection to complete.  If 
 selection to complete.  If 

-.I timeout
-is a zero pointer, the select blocks indefinitely.  To affect a poll, the
-.I timeout
-argument should be non-zero, pointing to a zero-valued timeval structure.
-.PP
+.Fa timeout
+is a nil pointer, the select blocks indefinitely.  To affect a poll, the
+.Fa timeout
+argument should be non-nil, pointing to a zero-valued timeval structure.
+.Pp

 Any of
 Any of

-.IR readfds ,
-.IR writefds ,
+.Fa readfds ,
+.Fa writefds ,

 and
 and

-.I exceptfds
-may be given as zero pointers if no descriptors are of interest.
-.SH "RETURN VALUE
-.I Select
+.Fa exceptfds
+may be given as nil pointers if no descriptors are of interest.
+.Sh RETURN VALUES
+.Fn Select

 returns the number of ready descriptors that are contained in
 the descriptor sets,
 returns the number of ready descriptors that are contained in
 the descriptor sets,

-or \-1 if an error occurred.
-If the time limit expires then
-.I select
+or -1 if an error occurred.
+If the time limit expires,
+.Fn select

 returns 0.
 If
 returns 0.
 If

-.I select
+.Fn select

 returns with an error,
 including one due to an interrupted call,
 the descriptor sets will be unmodified.
 returns with an error,
 including one due to an interrupted call,
 the descriptor sets will be unmodified.

-.SH "ERRORS
-An error return from \fIselect\fP indicates:
-.TP 15
-[EBADF]
+.Sh ERRORS
+An error return from
+.Fn select
+indicates:
+.Bl -tag -width Er
+.It Bq Er EBADF

 One of the descriptor sets specified an invalid descriptor.
 One of the descriptor sets specified an invalid descriptor.

-.TP 15
-[EINTR]
+.It Bq Er EINTR

 A signal was delivered before the time limit expired and
 before any of the selected events occurred.
 A signal was delivered before the time limit expired and
 before any of the selected events occurred.

-.TP 15
-[EINVAL]
+.It Bq Er EINVAL

 The specified time limit is invalid.  One of its components is
 negative or too large.
 The specified time limit is invalid.  One of its components is
 negative or too large.

-.SH SEE ALSO
-accept(2), connect(2), read(2), write(2), recv(2), send(2), getdtablesize(2)
-.SH BUGS
+.El
+.Sh SEE ALSO
+.Xr accept 2 ,
+.Xr connect 2 ,
+.Xr read 2 ,
+.Xr write 2 ,
+.Xr recv 2 ,
+.Xr send 2 ,
+.Xr getdtablesize 2
+.Sh BUGS

 Although the provision of
 Although the provision of

-.IR getdtablesize (2)
+.Xr getdtablesize 2

 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.
 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.

-The default size FD_SETSIZE (currently 256) is somewhat larger than
+The default size
+.Dv FD_SETSIZE
+(currently 256) is somewhat larger than

 the current kernel limit to the number of open files.
 the current kernel limit to the number of open files.

-However, in order to accomodate programs which might potentially
+However, in order to accommodate programs which might potentially

 use a larger number of open files with select, it is possible
 to increase this size within a program by providing
 use a larger number of open files with select, it is possible
 to increase this size within a program by providing

-a larger definition of FD_SETSIZE before the inclusion of <sys/types.h>.
-.PP
-.I Select
+a larger definition of
+.Dv FD_SETSIZE
+before the inclusion of
+.Aq Pa sys/types.h .
+.Pp
+.Fn Select

 should probably return the time remaining from the original timeout,
 if any, by modifying the time value in place.
 This may be implemented in future versions of the system.
 Thus, it is unwise to assume that the timeout value will be unmodified
 by the
 should probably return the time remaining from the original timeout,
 if any, by modifying the time value in place.
 This may be implemented in future versions of the system.
 Thus, it is unwise to assume that the timeout value will be unmodified
 by the

-.I select
+.Fn select

 call.
 call.

+.Sh HISTORY
+The
+.Nm
+function call appeared in
+.Bx 4.2 .