NAME

     select, FD_CLR, FD_ISSET, FD_SET, FD_ZERO - synchronous  I/O
     multiplexing


SYNOPSIS

     #include <sys/select.h>

     int select(int nfds, fd_set *readfds, fd_set *writefds, fd_set *errorfds, struct timeval *timeout)

     void FD_CLR(int fd, fd_set *fdset)
     int FD_ISSET(int fd, fd_set *fdset)
     void FD_SET(int fd, fd_set *fdset)
     void FD_ZERO(fd_set *fdset)


DESCRIPTION

     Select examines the  file  descriptors  given  in  the  sets
     readfds,  writefds,  and  errorfds, up to and including file
     descriptor nfds-1 , for  reading,  writing,  or  exceptional
     conditions, respectively.  Select currently supports regular
     files, pipes, named pipes, inet, and  tty  file  descriptors
     (including pty).

     If the readfds argument is not a null pointer, it points  to
     an  object  of  type fd_set that on input specifies the file
     descriptors to be checked for being ready to  read,  and  on
     output  indicates  which file descriptors are ready to read.
     Writefds and errorfds have an  analogous  meaning  for  file
     descriptors  to  be checked for being ready to read, respec-
     tively have pending exceptional (error) conditions.