To write OS independent REXX programs, you can use the PARSE SOURCE statement to distinguish between the different platforms (see example below and the chapter about PARSE SOURCE. The chapter titled Force a REXX program to run in a special way also discusses the use of PARSE SOURCE to identify the environment in which a REXX program is running and then process conditional commands.
When writing programs for use on other platforms in addition to OS/2, remember that some of the features and functions in OS/2 REXX are not implemented in REXX on other platforms (or may be implemented in a different manner)!
(see REXXTRY.CMD for another example for OS independent REXX programs)
/* ------------------------------------------------------------------ */
/* */
/* APPLICATION - Cross Platform - CMS, OS/2 2.0 and TSO */
/* FUNCTION - Merge 4 comma-delimited input files into an */
/* outputfile, tagging each record with the name of */
/* it's corresponding input file */
/* USE: OS/2 - MERGE f1.ext,f2.ext,f3.ext,f4.ext,outfile.ext */
/* TSO - MERGE f1.qlf,f2.qlf,f3.qlf,f4.qlf,outfile.qlf */
/* CMS - MERGE fn1 ft1 fm1,fn2 ft2 fm2,...fm4,ofn oft ofm */
/* AUTHOR - Michel Plungjan April '93 */
/* (see EMail Addresses) */
/* */
/* History: */
/* 12.12.1995 /bs */
/* - reformatted and added some comments */
/* 26.02.1996 /bs */
/* - corrected a bug in the TSO read secition according to */
/* information from Michel Plungjan */
/* */
/* ------------------------------------------------------------------ */
arg InFile.1 "," InFile.2 "," InFile.3 "," InFile.4 "," Merged
if InFile.1 = "/?" then
signal HELP;
call INIT
j = 0;
do i = 1 to 4
FileName = Infile.i
call READFILE;
if InRec.0 > 0 then
do k = 1 to InRec.0
j = j + 1
OutRec.j = strip(InRec.k,"T") substr(FileName,1,4)
end; /* do k = 1 to InRec.0 */
end; /* do i = 1 to 4 */
if j > 0 then
do
OutRec.0 = j;
call WRITEFILE;
end /* if j > 0 then */
else
do
XReason = "Input files empty...";
XRc = 8;
SIGNAL ABNORMAL_END
end; /* else */
SIGNAL NORMAL_END;
/* ------------------------------------------------------------------ */
/* */
READFILE:
select
when sys = 'CMS' then
do
/* --------------------- code for CMS ------------------------------- */
'EXECIO * DISKR' FileName '(FINIS STEM INREC.'
hrc = rc
if hrc <> 0 then
do
XRc = hrc
XReason = 'Error when reading' FileName 'dataset'
SIGNAL ABNORMAL_END
end /* if hrc <> 0 then */
end /* CMS */
when sys = 'TSO' then
do
/* --------------------- code for TSO ------------------------------- */
'ALLOC DA('FileName') FI(INDD) SHR'
hrc = rc
if hrc <> 0 then
do
XRc = hrc
XReason = 'Allocation error of' FileName 'dataset'
SIGNAL ABNORMAL_END
end
'EXECIO * DISKR INDD (FINIS STEM INREC.' /* v2.10 */
hrc = rc
if hrc <> 0 then
do
XRc = hrc
XReason = 'Error when reading' FileName 'dataset'
SIGNAL ABNORMAL_END
end /* if hrc <> 0 then */
'FREE FI(INDD)'
hrc = rc
if hrc <> 0 then
do
XRc = hrc
XReason = 'Error when freeing' FileName 'dataset, DDName INDD'
SIGNAL ABNORMAL_END
end /* if hrc <> 0 then */
end /* TSO */
when sys = 'OS/2' then
do
/* --------------------- code for OS/2 ------------------------------ */
do ii = 1 while lines(filename) > 0
InRec.ii = linein(FileName)
end; /* do ii = 1 while lines( fileName) > 0 */
InRec.0 = ii - 1
if (stream(FileName,'S') <> 'READY') then
do
XRc = 1
XReason = 'Error when reading' InFile ,
'file, Error indicator is 'stream(FileName,'D')
SIGNAL ABNORMAL_END
end /* I/O Error */
end /* OS/2 */
otherwise
do
/* --------------------- unknown OS --------------------------------- */
XReason = 'This program does not know how the environment' sys,
'uses I/O, please contact author'
XRc = 8
SIGNAL ABNORMAL_END
end /* otherwise */
end /* Select */
return
/* ------------------------------------------------------------------ */
/* */
WRITEFILE:
select
when sys = 'CMS' then
do
/* --------------------- code for CMS ------------------------------- */
'EXECIO 'OutRec.0 'DISKW 'Merged '0 F 80 (FINIS STEM OUTREC.'
hrc = rc
if hrc <> 0 then
do
XRc = hrc
XReason = 'Error when writing' Merged 'dataset'
SIGNAL ABNORMAL_END
end /* if hrc <> 0 then */
end /* CMS */
when sys = 'TSO' then
do
/* --------------------- code for TSO ------------------------------- */
'ALLOC DA('Merged') FI(OUTDD) SHR' /* File must already exist */
hrc = rc
if hrc <> 0 then
do
XRc = hrc
XReason = 'Allocation error of' Merged 'dataset'
SIGNAL ABNORMAL_END
end /* if hrc <> 0 then */
'EXECIO' OutRec.0 'DISKW OUTDD (FINIS STEM OUTREC.'
hrc = rc
if hrc <> 0 then
do
XRc = hrc
XReason = 'Error when writing' Merged 'dataset'
SIGNAL ABNORMAL_END
end /* if hrc <> 0 then */
'FREE FI(OUTDD)'
hrc = rc
if hrc <> 0 then
do
XRc = hrc
XReason = 'Error when freeing' Merged 'dataset, DDName OUTDD'
SIGNAL ABNORMAL_END
end /* if hrc <> 0 then */
end /* TSO */
when sys = 'OS/2' then
do
/* --------------------- code for OS/2 ------------------------------ */
do i = 1 to OutRec.0
Dummy = lineout(Merged,OutRec.i);
end; /* do i = 1 to OutRec.0 */
rc = stream(Merged,'c','close')
/* please put your own OS/2 error checking here */
end /* OS/2 */
otherwise
do
/* --------------------- unknown OS --------------------------------- */
XReason = 'This program does not know how the environment' sys,
'uses I/O, please contact author'
XRc = 8
SIGNAL ABNORMAL_END
end /* otherwise */
end /* Select */
return;
/* ------------------------------------------------------------------ */
/* init global variables and get the current OS (in the var SYS) */
/* */
INIT:
true = 1;
false = 0;
XReason = 'Files merged, you may now sort the file 'Merged;
XRc = 0
parse source sys .
return
/* ------------------------------------------------------------------ */
/* show the usage help */
/* */
HELP:
do i = 1 until pos('* ---',sourceline(i)) > 0
say strip(sourceline(i))
end /* do i = 1 ... */
exit;
/* ------------------------------------------------------------------ */
/* */
ABNORMAL_END:
say 'Program stopped due to'
/* ------------------------------------------------------------------ */
/* */
NORMAL_END:
say XReason 'return code:' Xrc
exit