unixdev.net


Switch to SpeakEasy.net DSL

The Modular Manual Browser

Home Page
Manual: (v7man)
Page:
Section:
Apropos / Subsearch:
optional field

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 returned from an open, pipe, or creat call, dup
       allocates another file descriptor synonymous 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 (approximately 19).  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.

ASSEMBLER
       (dup = 41.)
       (file descriptor in r0)
       (new file descriptor in r1)
       sys dup
       (file descriptor in r0)

       The dup2 entry is implemented by adding 0100 to fildes.



                                                                        DUP(2)