/*
	--- Version 3.3 91-11-21 16:12 ---

   EXEC.H: EXEC function with memory swap - Main function header file.

   Public domain software by

        Thomas Wagner
        Ferrari electronic GmbH
        Beusselstrasse 27
        D-1000 Berlin 21
        Germany
*/


extern int do_exec (char *xfn, char *pars, int spawn, unsigned needed,
						  char **envp);

/*>e
   The EXEC function.

      Parameters:

         xfn      is a string containing the name of the file
                  to be executed. If the string is empty,
                  the COMSPEC environment variable is used to
                  load a copy of COMMAND.COM or its equivalent.
                  If the filename does not include a path, the
                  current PATH is searched after the default.
                  If the filename does not include an extension,
                  the path is scanned for a COM, EXE, or BAT file 
                  in that order.

         pars     The program parameters.

         spawn    If 0, the function will terminate after the 
                  EXECed program returns, the function will not return.

                  NOTE: If the program file is not found, the function 
                        will always return with the appropriate error 
                        code, even if 'spawn' is 0.

                  If non-0, the function will return after executing the
                  program. If necessary (see the "needed" parameter),
                  memory will be swapped out before executing the program.
                  For swapping, spawn must contain a combination of the 
                  following flags:

                     USE_EMS  (0x01)  - allow EMS swap
                     USE_XMS  (0x02)  - allow XMS swap
                     USE_FILE (0x04)  - allow File swap

                  The order of trying the different swap methods can be
                  controlled with one of the flags

                     EMS_FIRST (0x00) - EMS, XMS, File (default)
                     XMS_FIRST (0x10) - XMS, EMS, File

                  If swapping is to File, the attribute of the swap file
                  can be set to "hidden", so users are not irritated by
                  strange files appearing out of nowhere with the flag

                     HIDE_FILE (0x40)    - create swap file as hidden

                  and the behaviour on Network drives can be changed with

                     NO_PREALLOC (0x100) - don't preallocate
                     CHECK_NET (0x200)   - don't preallocate if file on net.

                  This checking for Network is mainly to compensate for
                  a strange slowdown on Novell networks when preallocating
                  a file. You can either set NO_PREALLOC to avoid allocation
                  in any case, or let the prep_swap routine decide whether
                  to do preallocation or not depending on the file being
                  on a network drive (this will only work with DOS 3.1 or 
                  later).

         needed   The memory needed for the program in paragraphs (16 Bytes).
                  If not enough memory is free, the program will 
                  be swapped out. 
                  Use 0 to never swap, 0xffff to always swap. 
                  If 'spawn' is 0, this parameter is irrelevant.

         envp     The environment to be passed to the spawned
                  program. If this parameter is NULL, a copy
                  of the parent's environment is used (i.e.
                  'putenv' calls have no effect). If non-NULL,
                  envp must point to an array of pointers to
                  strings, terminated by a NULL pointer (the
                  standard variable 'environ' may be used).

      Return value:

         0x0000..00FF: The EXECed Program's return code

         0x0101:       Error preparing for swap: no space for swapping
         0x0102:       Error preparing for swap: program too low in memory

         0x0200:       Program file not found
         0x0201:       Program file: Invalid drive
         0x0202:       Program file: Invalid path
         0x0203:       Program file: Invalid name
         0x0204:       Program file: Invalid drive letter
         0x0205:       Program file: Path too long
         0x0206:       Program file: Drive not ready
         0x0207:       Batchfile/COMMAND: COMMAND.COM not found
         0x0208:       Error allocating temporary buffer

         0x03xx:       DOS-error-code xx calling EXEC

         0x0400:       Error allocating environment buffer

         0x0500:       Swapping requested, but prep_swap has not 
                       been called or returned an error.
         0x0501:       MCBs don't match expected setup
         0x0502:       Error while swapping out

         0x0600:       Redirection syntax error
         0x06xx:       DOS error xx on redirection
<*/

/*>d
   Die EXEC Funktion.

      Parameter:

         xfn      ist ein String mit dem Namen der auszuf乭renden Datei.
                  Ist der String leer, wird die COMSPEC Umgebungsvariable
                  benutzt um COMMAND.COM oder das Equivalent zu laden.
                  Ist kein Pfad angegeben, wird nach dem aktuellen Pfad
                  der in der PATH Umgebungsvariablen angegebene Pfad
                  durchsucht.
                  Ist kein Dateityp angegeben, wird der Pfad nach
                  einer COM oder EXE Datei (in dieser Reihenfolge) abgesucht.

         pars     Die Kommandozeile

         spawn    Wenn 0, wird der Programmlauf beendet wenn das
                  aufgerufene Programm zur乧kkehrt, die Funktion kehrt
                  nicht zur乧k.

                  HINWEIS: Wenn die auszuf乭rende Datei nicht gefunden
                        wird, kehrt die Funktion mit einem Fehlercode
                        zur乧k, auch wenn der 'spawn' Parameter 0 ist.

                  Wenn nicht 0, kehrt die Funktion nach Ausf乭rung des
                  Programms zur乧k. Falls notwendig (siehe den Parameter
                  "needed") wird der Programmspeicherbereich vor Aufruf 
                  ausgelagert.
                  Zur Auslagerung mu