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 arguments 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, Copyright (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.opengroup.org/unix/online.html .