sys_select.h(7POSIX)

PROLOG
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.

NAME
sys/select.h — select types

SYNOPSIS

#include <sys/select.h>

DESCRIPTION
The <sys/select.h> header shall define the timeval structure, which shall include at least the following members:

    time_t         tv_sec      Seconds.
    suseconds_t    tv_usec     Microseconds.

The <sys/select.h> header shall define the time_t and suseconds_t types as described in <sys/types.h>.

The <sys/select.h> header shall define the sigset_t type as described in <signal.h>.

The <sys/select.h> header shall define the timespec structure as described in <time.h>.

The <sys/select.h> header shall define the fd_set type as a structure.

The <sys/select.h> header shall define the following symbolic constant, which shall have a value suitable for use in #if preprocessing directives:

FD_SETSIZE
    Maximum number of file descriptors in an fd_set structure.

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> and <time.h>.

The following sections are informative.

APPLICATION USAGE
None.

RATIONALE
None.

FUTURE DIRECTIONS
None.

SEE ALSO
<signal.h>, <sys_time.h>, <sys_types.h>, <time.h>

The System Interfaces volume of POSIX.1-2017, pselect()

COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. 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.opengroup.org/unix/online.html .

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .