[Overview][Constants][Types][Procedures and functions][Index] Reference for unit 'BaseUnix' (#rtl)


Duplicate one filehandle to another


Source position: bunxh.inc line 39

function FpDup2(

  fildes: cint;

  fildes2: cint


function FpDup2(

  var oldfile: text;

  var newfile: text


function FpDup2(

  var oldfile: file;

  var newfile: file



Makes fildes2 or NewFile an exact copy of fildes or OldFile, after having flushed the buffer of OldFile in the case of text or untyped files.

After a call to fdup2, the 2 file descriptors point to the same physical device (a file, socket, or a terminal).

NewFile can be an assigned file. If newfile or fildes was open, it is closed first. Due to the buffering mechanism of Pascal, this has not the same functionality as the dup2 call in C. The internal Pascal buffers are not the same after this call, but when the buffers are flushed (e.g. after output), the output is sent to the same file. Doing an lseek will, however, work as in C, i.e. doing a lseek will change the fileposition in both files.

The function returns the new file descriptor number, on error -1 is returned, and the error can be retrieved with fpgeterrno


In case of error, the following error codes can be reported:

OldFile (or fildes) hasn't been assigned.
Maximum number of open files for the process is reached.

See also



Duplicate a file handle


program Example32;

{ Program to demonstrate the FpDup2 function. }

uses BaseUnix;

var f : text;
    i : longint;

  Assign (f,'text.txt');
  Rewrite (F);
  For i:=1 to 10 do writeln (F,'Line : ',i);
  if fpdup2 (output,f)=-1 then
    Writeln ('Dup2 Failed !');
  writeln ('This is written to stdout.');
  writeln (f,'This is written to the dup file, and flushed');
  { Remove file. Comment this if you want to check flushing.}
  fpUnlink ('text.txt');

Documentation generated on: Mar 17 2017