sunos man page for dup

dup(2)								   System Calls 							    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 descriptor.

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       ENOLINK	       The fildes argument is on a remote machine and the link to that machine is no longer active.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

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |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), standards(5)

SunOS 5.10							    28 Dec 1996 							    dup(2)