glenda.party
term% ls -F
term% pwd
$home/manuals/unix_v8/2/dup
term% cat index.txt
DUP(2)                        System Calls Manual                       DUP(2)



NAME
       dup, dup2 - duplicate an open file descriptor

SYNOPSIS
       dup(fildes)
       int fildes;

       dup2(fildes, fildes2)
       int fildes, fildes2;

DESCRIPTION
       Given  a  file descriptor dup allocates another file descriptor synony‐
       mous with the original.  The new file descriptor is returned.

       In the second form of the call, fildes is a file  descriptor  referring
       to  an  open  file, and fildes2 is a non-negative integer less than the
       maximum value allowed  for  file  descriptors  (currently  127).   Dup2
       causes fildes2 to refer to the same file as fildes.  If fildes2 already
       referred to an open file, it is closed first.

SEE ALSO
       creat(2), open(2), close(2), pipe(2)

DIAGNOSTICS
       The value -1 is returned if: the  given  file  descriptor  is  invalid;
       there are already too many open files.



                                                                        DUP(2)