Hi Larry,

Here is a message I posted to 3000-L on this topic:

regards,
Jeff Vance, CSY

===============================

Date:         Wed, 15 Dec 1999 18:23:22 -0700
Subject:      Re: Read record from file into a variable.

> Can someone send me an example of reading a record from a flat
> file, into a Variable.

I am assuming you want to know how to do this via the CI.  The basic
problem is that the CI's IO redirection opens the file and causes
the record pointer to be set to the beginning.  This is done each time the
IO redirdction is encountered by the CI.  Thus, if you try to
read from a file in a WHILE loop using the INPUT command, you
will read only the first record each iteration.  Below are some ways
to overcome this restriction.

Method 1: using a MSG file.
---------------------------
  PROS: simple, easy to maintain, and an easy way to read small files
        or make "quick and dirty" scripts.
  CONS: slow, especially if the file is long.

Basic idea:
  - use a file equation to create a MSG file
  - redirect output to this MSG file
  - use the INPUT command to read from the MSG file via IO
    redirection.

Example:
   PARM p1, p2, ...
   #comments...
   file myfile;MSG
   errclear
   continue
   listf !p1,2 >*myfile
   if hpcierr = 0 then
      setvar eof FINFO("*myfile","eof")
      while setvar(eof,eof-1) > 0 do
         input record_var <*myfile
         showvar record_var  ... etc...
      endwhile
   endif
   reset myfile
   deletevar record_var,eof


Method 2: using a flat file.
----------------------------
  PROS: most efficient way in the CI to read files.
  CONS: less intuitive and more effort to author.

Basic idea:
  - create a file via IO redirection
  - xeq the same script with the script's input redirected to the
    file created in step 1.
  - use the INPUT command or input() function to read from the
    file (with no IO redirection since the input for the entire
    script is redirected here).

Example:
   PARM p1, p2, ..., entry=main
   #comments...
   if "!entry" = "main" then
      # in the main part of the script
      errclear
      continue
      listf !p1,2 >myfile
      if hpcierr = 0 then
         # execute same script with input redirected
         xeq !HPFILE !p1, !p2, ... entry=alternate <myfile
      endif
      deletevar record_var,eof
      return

   elseif "!entry" = "alternate" then
      # in the 'alternate' script entry point
      setvar eof FINFO(HPSTDIN,"eof")
      while setvar(eof,eof-1) > 0 do
         setvar record_var input()
         showvar record_var  ... etc..
      endwhile
      return
   endif


Method 3: using PRINT to get an individual record.
--------------------------------------------------
  PROS: I've seen this approach used many times so it must be
        intuitive.
  CONS: inefficient, ok for small files.

Basic idea:
  - create a file via IO redirection.
  - use the PRINT;start=;end= to create another file with 1 record.
  - use the INPUT command to read from the one record file via IO
    redirection.

Example:
   PARM p1, p2, ...
   #comments...
   errclear
   continue
   listf !p1,2 >myfile
   if hpcierr = 0 then
      setvar eof FINFO("myfile","eof")
      setvar i 0
      while setvar(i,i+1) <= eof do
         print myfile;start=!i;end=!i >myfile2
         input record_var <myfile2
         showvar record_var  ... etc...
      endwhile
   endif
   deletevar record_var,eof,i

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