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6.15.3 Overcome some differences between Dos and Unix

The following listing contains the interface of the DosUnix unit.

This unit is there to overcome some of those differences between Dos and Unix systems that are not automatically hidden by GPC and the Run Time System. Currently features translation of bash style input/output redirections (foo 2>&1) into redir calls for DJGPP (redir -eo foo) and a way to read files with Dos CR/LF pairs on any system.

When necessary, new features will be added to the unit in future releases.

     { Some routines to support writing programs portable between Dos and
       Unix. Perhaps it would be a good idea not to put features to make
       Dos programs Unix-compatible (shell redirections) and vice versa
       (reading Dos files from Unix) together into one unit, but rather
       into two units, DosCompat and UnixCompat or so -- let's wait and
       see, perhaps when more routines suited for this/these unit(s) will
       be found, the design will become clearer ...
       Copyright (C) 1998-2005 Free Software Foundation, Inc.
       Author: Frank Heckenbach <>
       This file is part of GNU Pascal.
       GNU Pascal is free software; you can redistribute it and/or modify
       it under the terms of the GNU General Public License as published
       by the Free Software Foundation; either version 2, or (at your
       option) any later version.
       GNU Pascal is distributed in the hope that it will be useful, but
       WITHOUT ANY WARRANTY; without even the implied warranty of
       General Public License for more details.
       You should have received a copy of the GNU General Public License
       along with GNU Pascal; see the file COPYING. If not, write to the
       Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
       02111-1307, USA.
       As a special exception, if you link this file with files compiled
       with a GNU compiler to produce an executable, this does not cause
       the resulting executable to be covered by the GNU General Public
       License. This exception does not however invalidate any other
       reasons why the executable file might be covered by the GNU
       General Public License. }
     {$if __GPC_RELEASE__ < 20030412}
     {$error This unit requires GPC release 20030412 or newer.}
     unit DosUnix;
     uses GPC;
     { This function is meant to be used when you want to invoke a system
       shell command (e.g. via Execute or Exec from the Dos unit) and
       want to specify input/output redirections for the command invoked.
       It caters for the different syntax between DJGPP (with the redir
       utility) and other systems.
       To use it, code your redirections in bash style (see the table
       below) in your command line string, pass this string to this
       function, and the function's result to Execute or the other
       The function translates the following bash style redirections
       (characters in brackets are optional) into a redir call under Dos
       systems except EMX, and leave them unchanged under other systems.
       Note: redir comes with DJGPP, but it should be possible to
       install it on other Dos systems as well. OS/2's shell, however,
       supports bash style redirections, I was told, so we don't
       translate on EMX.
       [0]<     file      redirect standard input from file
       [1]>[|]  file      redirect standard output to file
       [1]>>    file      append standard output to file
       [1]>&2             redirect standard output to standard error
       2>[|]    file      redirect standard error to file
       2>>      file      append standard error to file
       2>&1               redirect standard error to standard output
       &> file            redirect both standard output and standard
                          error to file }
     function  TranslateRedirections (const Command: String) = s:
     { Under Unix, translates CR/LF pairs to single LF characters when
       reading from f, and back when writing to f. Under Dos, does
       nothing because the run time system alrady does this job. In the
       result, you can read both Dos and Unix files, and files written
       will be Dos. }
     procedure AssignDos (var f: AnyFile; const FileName: String);
     { Translates a character from the "OEM" charset used under Dos to
       the ISO-8859-1 (Latin1) character set. }
     function  OEM2Latin1 (ch: Char): Char;
     function  OEM2Latin1Str (const s: String) = r: TString;
     { Translates a character from the ISO-8859-1 (Latin1) character set
       to the "OEM" charset used under Dos. }
     function  Latin12OEM (ch: Char): Char;
     function  Latin12OEMStr (const s: String) = r: TString;