<sys/select.h>(0P)                                  POSIX Programmer's Manual                                 <sys/select.h>(0P)



NAME
       sys/select.h - select types

SYNOPSIS
       #include <sys/select.h>

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


              time_t         tv_sec      Seconds.
              suseconds_t    tv_usec     Microseconds.

       The time_t and suseconds_t types shall be defined as described in <sys/types.h> .

       The sigset_t type shall be defined as described in <signal.h> .

       The timespec structure shall be defined as described in <time.h> .

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

       Each of the following may be declared as a function, or defined as a macro, or both:

       void FD_CLR(int fd, fd_set *fdset)

              Clears the bit for the file descriptor fd in the file descriptor set fdset.

       int FD_ISSET(int fd, fd_set *fdset)

              Returns  a  non-zero value if the bit for the file descriptor fd is set in the file descriptor set by fdset, and 0
              otherwise.

       void FD_SET(int fd, fd_set *fdset)

              Sets the bit for the file descriptor fd in the file descriptor set fdset.

       void FD_ZERO(fd_set *fdset)

              Initializes the file descriptor set fdset to have zero bits for all file descriptors.


       If implemented as macros, these may evaluate their arguments more than once, so applications should ensure that the argu-
       ments they supply are never expressions with side effects.

       The following shall be defined as a macro:

       FD_SETSIZE

              Maximum number of file descriptors in an fd_set structure.


       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>, <sys/time.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  IEEE Std 1003.1-2001,  pselect(),
       select()

COPYRIGHT
       Portions  of  this  text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for
       Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6,  Copy-
       right (C) 2001-2003 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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                            <sys/select.h>(0P)