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Piping tail -f to fold: tail -f log.txt | fold


From: Philip Durbin
Subject: Piping tail -f to fold: tail -f log.txt | fold
Date: Fri, 09 Jan 2009 09:46:35 -0500
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.0.14eol) Gecko/20081209 Red Hat/1.0.9-32.el4 SeaMonkey/1.0.9

To word wrap the output of a growing log file I tried. . .
$ tail -f log.txt | fold -s
. . . and it works fine on NetBSD and Mac OS X, but on the two Linux distributions I tried (Red Hat and SUSE) I get no output.

As a work around for Linux I can combine tail without -f and watch. . .
$ watch "tail log.txt | fold -s"
. . . but because I'm likely to miss some lines, I threw together a Perl script instead:

#!/usr/bin/perl
use strict;
use warnings;
use File::Tail;
use Text::Wrap;
$Text::Wrap::columns = 72;
my $file = File::Tail->new('/tmp/log.txt');
while ( defined( my $line = $file->read ) ) {
    print wrap( '', '', $line );
}

Despite my workarounds, I'm still left wondering. . .

Can piping tail -f to fold be made to work on Linux the way it works on BSD?

If not, can anyone please explain the difference in the implementation of fold?

Thanks in advance!

Phil




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