Automate the boring stuff with Python states: To indicate that the entire string must match the regex, that is, it’s not enough for a match to be made on some subset of the string, use the ^ and $ together. How can I convert a regular expression to work in a Bash script? You could use a look-ahead assertion: (? (*.jpg|a.jpg) should not match, because a.jpg matched both patterns, and the ? By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy. Wrong. * mksh does not support POSIX character classes. Then, in the first regex, we replaced . How can I check if a directory exists in a Bash shell script? Thanks for contributing an answer to Stack Overflow! In a bash script, why does. However, if I enter that same syntax into grep on the command line, I get an unexpected result: shell scripts. is "zero or one", right? If statement with a regex in bash not working, Current code marking REGEX as invalid even though it is valid via REGEX checkers. It's easy to formulate a regex using what you want to match. If the string does not match the pattern, an exit code of 1 ("false") is returned. The set of extglob quantifiers supported by ksh88 are identical to those supported by Bash, mksh, ksh93, and zsh. But it always says that your regex didn't match but the regex tool shows that it matches with my regular explanation. For each argument string, match stops when it hits the first matching line of the file. Okay. Returns 1. One easy way to exclude text from a match is negative lookbehind: w+b(?