Message-ID: <42832A77.9090406@lancaster.ac.uk>
Date: 2005-05-12T10:05:43Z
From: Barry Rowlingson
Subject: R2.1.0: Bug in list.files
In-Reply-To: <42831B79.6070308@statistik.uni-dortmund.de>
Uwe Ligges wrote:
> Please read about regular expressions (!!!) and try to understand that
> ".txt" also finds "Not_a_txt_file.xls" ....
The confusion here is between regular expressions and wildcard
expansion known as 'globbing'. The two things are very different, and
use characters such as '*' '.' and '?' in different ways.
There's added confusion when people come from a DOS background, where
commands did their own thing when given '*' as parameter. The DOS command:
RENAME *.FOO *.BAR
did what seems obvious, renaming all the .FOO files to .BAR, but on a
unix machine doing this with 'mv' can be destructive!
In short (and slightly simplified), a '*' when expanded as a wildcard
in a glob matches any string, whereas a '*' in a regular expression
(regexp), matches the previous character 0 or more times. This is why
"*.zip" is flagged as invalid now - there's no character before the "*".
That should be enough clues to send you on your way.
Baz