dup2(3C)

NAME
     dup2 - duplicate an open file descriptor

SYNOPSIS
     #include <unistd.h>

     int dup2 (int fildes, int fildes2);

DESCRIPTION
     fildes is a file descriptor referring to an open file, and fildes2 is a
     non-negative integer less than the maximum number of open files
     available.  dup2 causes fildes2 to refer to the same file as fildes.  If
     fildes2 already referred 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.

     dup2 will fail if one or more of the following are true:

     EBADF          fildes is not a valid open file descriptor.

     EBADF          fildes2 is negative or greater than or equal to the
                    maximum number of open files available.

     EINTR          a signal was caught during the dup2 call.

     EMFILE         The maximum number of file descriptors are currently open.

SEE ALSO
     creat(2), close(2), exec(2), fcntl(2), open(2), pipe(2), lockf(3C),
     limits(4)

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.