sys_select.h(3)            POSIX Programmer's Manual           sys_select.h(3)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

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 .



IEEE/The Open Group                  2017                      sys_select.h(3)
