grep backslash in negative lookbehind
bash, grep, regex
Solution
Neither standard nor extended regular expressions support the look behind. Use Perl compatible regexes:
grep -P '(?<!\\)xxx' test.tex
Problem
I want to find the number of occurrences of `XXX` in my latex document that are not in the form of a command as `\XXX`. Therefore I am looking for occurrences that are not preceded by a backslash. I tried the following: ``` grep -c -e '(?<!\)XXX' test.tex #result: grep: Unmatched ) or \) grep -c -e '(?<!\\)XXX' test.tex #result: 0 grep -c -e "(?<!\\)XXX" test.tex #result: -bash: !\\: event not found ``` none of them work as intended. In fact I don't understand the last error message at all. My test.tex contains only the following lines ``` %test.tex XXX \XXX ``` So the expected result is `1`. Any ideas? Ps.: I am working in bash.