plan9 man page for dup2

dup2(3C)						   Standard C Library Functions 						  dup2(3C)

NAME
       dup2 - duplicate an open file descriptor

SYNOPSIS
       #include <unistd.h>

       int dup2(int fildes, int fildes2);

DESCRIPTION
       The dup2() function causes the file descriptor fildes2 to refer to the same file as fildes. The fildes argument is a file descriptor refer-
       ring to an open file, and fildes2 is a non-negative integer less than the current value for the maximum number  of  open  file  descriptors
       allowed	the  calling  process.	 See  getrlimit(2).  If fildes2 already refers to an open file, not fildes, it is closed first. If fildes2
       refers to fildes, or if fildes is not a valid open file descriptor, fildes2 will not be closed first.

       The dup2() function is equivalent to  fcntl(fildes, F_DUP2FD, fildes2).

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 dup2() function will fail if:

       EBADF	       The fildes argument is not a valid open file descriptor.

       EBADF	       The files2 argument is negative or is not less than the current resource limit returned by getrlimit(RLIMIT_NOFILE, ...).

       EINTR	       A signal was caught during the dup2() call.

       EMFILE	       The process has too many open files.  See  fcntl(2).

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), lockf(3C), attributes(5), standards(5)

SunOS 5.10							    19 Dec 2003 							  dup2(3C)