[GLLUG] tr

[Matt Graham]

On Monday 30 September 2002 11:59, after a long battle with technology, 
Melson, Paul wrote:
> According to my understanding of its syntax, this
> should work:
>
> tr -s '\134\156' '\040' < dumpfile.txt > newfile.txt
>
> In this instance, tr uses the octal values for '\' and 'n' and
> replaces them with the octal value for ' ' (space).  It does what it
> should do - replaces each '\n' with a ' ', but it's also matching on
> each 'n' and replacing it with a ' ', which causes a whole new set of
> problems.
>
> It seems to me that someone must've run across something like this in
> the past.  Ideas, suggestions, and slaps upside the head are all
> appreciated.  Anybody?

tr doesn't do regexp matching the way sed and perl do.  tr in this case 
is matching either '\' or 'n' and replacing either one with ' '.  This 
is not what you want.  I think you want this:

perl -pe 's#\\n# #g' < dumpfile.txt > newfile.txt

Perl handles "weird" characters like 0x0A and 0x0D in regexps in a more 
consistent way than sed does.  However, if this is a really large file 
(over a few hundred M) that doesn't have any newlines in it at all, 
Perl might choke since the -pe option makes it use the normal <> 
operator on STDIN, and the <> operator breaks on newlines by default... 
sucking several hundred M into RAM and then using the normal regexp 
engine on it could cause obvious problems.

-- 
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