On Sat, Nov 24, 2012 at 10:29:30PM +0000, Lawrence Steeger wrote: > Alex Chupin (achupin <achupin <at> cisco.com> writes: > > $ bash --version; s=12345;if [[ "$s" =~ '^[0-9]+$' ]]; then echo it is a > number; else echo it is NOT a number; fi
> The single quotes are being used in the match. If you remove them, > it will work. The second sentence is correct, but the first is not. The single quotes (or any other kind of quoting) override the =~ and cause the right hand side to be matched as a string, rather than as a regular expression (or even a glob). However, the quotes themselves are not being treated as literal characters. They are removed before the string comparison occurs. imadev:~$ x=abc; if [[ $x =~ 'abc' ]]; then echo match; fi match As others have already said, the best way to use =~ is to place the regular expression in a variable, and then use that variable without quotes on the right hand side of =~. re='^[st](uff)*$'; if [[ $string =~ $re ]]; then ...
