Some rexx tips:

To see if a file or directory exists,
   if stream(fn,'c','QUERY EXISTS')<>'' Then <it exists>
   if stream(fn,'c','QUERY EXISTS')='' Then <it doesn't exist>
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To write a file,
   j=lineout(fn,text,optional_line_number)
then to close it,
   j=stream(fn,'c','Close')
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To read a file,
   Do while lines(fn)
     line=linein(fn)
     ... do stuff with the line ...
   End
-------------------------------------------------------------------

To fix the "Cannot open message catalog rexxaix.cat" 
error message on an AIX 4 system,
   ln -s /local/lib/rexx/rexxaix.cat /usr/lib/nls/msg/C/rexxaix.cat
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To install REXX, get REXXAIX INSTALL & REXXAIX TARXBIN from
AIXTOOLS, download as binary, then
  uncompress rexxaix.tar.Z | tar -xvf -