dup(2)

NAME

     dup - duplicate an open file descriptor

SYNOPSIS

     #include <unistd.h>

     int dup(int fildes);

DESCRIPTION

     The dup() function returns a new file descriptor having  the
     following  in  common with the original open file descriptor
     fildes:

        o  same open file (or pipe)

        o  same file pointer  (that  is,  both  file  descriptors
           share one file pointer)

        o  same access mode (read, write or read/write).

     The new file descriptor is set to remain  open  across  exec
     functions (see fcntl(2)).

     The file descriptor returned is the lowest one available.

     The dup(fildes) function call is equivalent to:

          fcntl(fildes, F_DUPFD, 0)

RETURN VALUES

     Upon   successful   completion,   a   non-negative   integer
     representing  the file descriptor is returned. Otherwise, -1
     is returned and errno is set to indicate the error.

ERRORS

     The dup() function will fail if:

     EBADF The fildes argument is not a valid open file  descrip-
           tor.

     EINTR A signal was caught during the execution of the  dup()
           function.

     EMFILE
           The   process   has   too   many   open   files   (see
           getrlimit(2)).

     ENOLINK
           The fildes argument is on a  remote  machine  and  the
           link to that machine is no longer active.

ATTRIBUTES

     See attributes(5) for descriptions of the  following  attri-
     butes:

     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | MT-Level                    | Async-Signal-Safe           |
    |_____________________________|_____________________________|

SEE ALSO

     close(2),   creat(2),   exec(2),   fcntl(2),   getrlimit(2),
     open(2), pipe(2), dup2(3C), lockf(3C), attributes(5)