dup(2)                           UNIX System V                           dup(2)


NAME
      dup - duplicate an open file descriptor

SYNOPSIS
      #include <unistd.h>

      int dup(int fildes);

DESCRIPTION
      fildes is a file descriptor obtained from a creat, open, dup, fcntl,
      pipe, or ioctl system call.  dup returns a new file descriptor having the
      following in common with the original:

            Same open file (or pipe).

            Same file pointer (i.e., both file descriptors share one file
            pointer).

            Same access mode (read, write or read/write).

      The new file descriptor is set to remain open across exec system calls
      [see fcntl(2)].

      The file descriptor returned is the lowest one available.

      dup will fail if one or more of the following are true:

      EBADF          fildes is not a valid open file descriptor.

      EINTR          A signal was caught during the dup system call.

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

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                     is no longer active.

SEE ALSO
      close(2), creat(2), exec(2), fcntl(2), getrlimit(2), open(2), pipe(2),
      dup2(3C), lockf(3C).

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










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