regexp question
 

I use bash2.05.

echo "ab]" | grep '^[a-z]*$

How to add ']' in a set of acceptable symbols? \] doesn't work

'man regexp' explains how to do it, in the section titled 'Regular Expressions' (last paragraph).

I don't think grep handles regular expressions unless you give the -E or -G option. I could be wrong, but I don't know why they would include those options if grep handled regexps out-of-the-box.

Shortly speaking, RTFM, as usual:
[To include a literal ] place it first in the list. Similarly, to include a literal ^ place it anywhere but first. Finally, to include a literal - place it last]