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1 day ago my boss said that some text files could not be integrated with a search engine because the characters with a cedille on them were causing it to barf.

When I looked at this file in Emacs, I saw this \347 I did a bit of reading on how emacs sees a buffer as a sequence of 8-bit bytes unless you turn on various interpretation modes, and then went on about my business.

Next I went to and saw the offending character. Somehow the C with a cedille was being displayed by the Windows command window as a greek "tau". Which has ascii value 231. And sure enough the when I ran my file thru this program

use strict; my $file = shift or die 'must supply filename'; open my $fh, $file or die "couldnt open $file: $!"; $\="\n"; while (<$fh>) { # print $.,$/; my $char; while (/\G(.)/g) { ++$char; my $c=$1; if ($c =~ /[[:^print:]]/) { print "plain_text test failed on row $. with char # $char: <$c +>\n" . "Unicode Value: " . unpack('C', $c); print "context: " . substr($_, 0, $char+5); } } }
It said that the bad character was 231. But it also flagged a lot of other things in the file... possibly because one "wide bit" character was being interpreted as several 8-bit chars. And then I read on the utf8 pragma in the Perl standard docs. And I put use utf8 at the top of the program. And the presto-chango, only the cedille was detected.

What happened was that Perl saw my file as a sequence of Unicode characters instead of as a sequence of 8-bit bytes. So how does one decide Unicode characters are appropriate for their application? One takes a look at the Unicode Code Charts. So, after looking at these, I was certain of which Unicode values I wanted to accept but I was only fairly sure that the Perl POSIX :print: character class equivalent. So, I took the low road (or is that the high road?) and wrote this to determine whether to accept a string of text:

use utf8; my $U; while ($column =~ /\G(.)/g) { # WRONG! Thanks John M. Dlugosz $U = unpack('C', $1); $U = unpack('U', $1); # Now that's the ticket $U < 127 and $U > 31 or return; } return 1;

In reply to ASCII, Unicode, use utf8: My Story of Discovery by princepawn

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