Odd error with regular expression in grep

Question

I'm running the following command:

cat something | egrep "(abc|def)$"

On a server running Linux.

The same OS with kernel 2.6.18 gives the correct answer, while with 2.6.19 I get:

Illegal variable name.

Apparently the $ sign is causing the error, but the question is why is it behaving differently across kernels?

Is the version of grep the same? – Lucas Kauffman Apr 29 '12 at 15:17 — Lucas Kauffman, Apr 29 '12 at 15:17

score 3 · Accepted Answer · answered Apr 29 '12 at 15:38

3

1) Are you using the same type of shell on both machines?

2) Have you tried using single quotes, so that the shell doesn't try to interpret the dollar sign as a variable?

answered Apr 29 '12 at 15:38

Zee

46
1

score 1 · Answer 2 · answered Apr 29 '12 at 15:40

Its more likely this is an issue with the shell you're running. First, the quotes; when using single quotes, variables won't be replaced in the outcoming string. I.e.,

% VAR="hello"
% echo "$VAR world!"
hello world!
% eco '$VAR world!'
$VAR world!

In your case, its literally trying to execute $, but $ is not a valid variable name. If you use single quotes, the shell won't allow the dollar sign to be replaced.

Odd error with regular expression in grep

2 Answers2