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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 .