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From: Ralf Fassel <ralfixx@gmx.de>
Newsgroups: comp.lang.tcl
Subject: Re: File processing (was Event loop and http::geturl)
Date: Thu, 26 Jun 2025 12:14:24 +0200
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* Alan Grunwald <nospam.nurdglaw@gmail.com>
| My pseudo code is generally
>
| while !eof {
|     read a line
|     if line is not empty
|         do stuff
|     endif
| endwhile
>
| I used to be puzzled why I needed the test for non-emptiness. I never
| worked out why, nowadays I simply accept that's the way of things and
| do it.

If the read hits EOF, an empty line is returned which is not actually in
the file.  Depending on your data, this may or may not be a problem
(if you're not interested in empty lines in the data, then no problem).

Usually a better pattern for line-oriented data
on a channel in blocking mode is

  while {[gets $fd line] >= 0} {
    # line has been read, possibly empty
    ...
  }
  close $fd

HTH
R'