How to escape a previously unknown string in regular expression?

Question

I need to egrep a string that isn\'t known before runtime and that I\'ll get via shell variable (shell is bash, if that matters). Problem is, that string will c

Answer 1

Use the -F flag to make the PATTERN a fixed literal string

$ var="(.*+[a-z]){3}"
$ echo 'foo bar (.*+[a-z]){3} baz' | grep -F "$var" -o
(.*+[a-z]){3}