Use the double bracket syntax to use regular expressions (aka regex or regexp) in bash conditionals:
me@pc ~/tmp/bashregextest $ if [[ "foo/bar" =~ ^foo ]]; then echo 'yes'; else echo 'no'; fi
yes
me@pc ~/tmp/bashregextest $ if [[ "foo/bar" =~ ^bar ]]; then echo 'yes'; else echo 'no'; fi
no
Be sure to include the spaces between the double brackets and the conditional inside, otherwise you’ll get an error like this:
me@pc ~/tmp/bashregextest $ if [[ "foo/bar" =~ ^foo]]; then echo 'yes'; else echo 'no'; fi
bash: syntax error in conditional expression: unexpected token `;'
bash: syntax error near `;'
Source: Tutorial: Conditions in bash scripting (if statements)
