This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the corresponding Linux
manual page for details of Linux behavior), or the interface may not be
implemented on Linux.
sys/select.h — select types
header shall define the timeval
structure, which shall include at least the following members:
time_t tv_sec Seconds.
suseconds_t tv_usec Microseconds.
header shall define the time_t
types as described in <sys/types.h>
header shall define the sigset_t
described in <signal.h>
header shall define the timespec
structure as described in <time.h>
header shall define the fd_set
type as a
header shall define the following symbolic
constant, which shall have a value suitable for use in #if
- Maximum number of file descriptors in an fd_set
The following shall be declared as functions, defined as macros, or both. If
functions are declared, function prototypes shall be provided.
void FD_CLR(int, fd_set *);
int FD_ISSET(int, fd_set *);
void FD_SET(int, fd_set *);
void FD_ZERO(fd_set *);
If implemented as macros, these may evaluate their arguments more than once, so
applications should ensure that the arguments they supply are never
expressions with side-effects.
The following shall be declared as functions and may also be defined as macros.
Function prototypes shall be provided.
int pselect(int, fd_set *restrict, fd_set *restrict, fd_set *restrict,
const struct timespec *restrict, const sigset_t *restrict);
int select(int, fd_set *restrict, fd_set *restrict, fd_set *restrict,
struct timeval *restrict);
Inclusion of the <sys/select.h>
header may make visible all symbols
from the headers <signal.h>
The following sections are informative.
The System Interfaces volume of POSIX.1‐2008, pselect()
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2013 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
7, Copyright (C) 2013 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. (This is POSIX.1-2008 with the 2013
Technical Corrigendum 1 applied.) In the event of any discrepancy between this
version and the original IEEE and The Open Group Standard, the original IEEE
and The Open Group Standard is the referee document. The original Standard can
be obtained online at http://www.unix.org/online.html .
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