Bash - Regex
About
Multilingual Regular Expression Syntax (Pattern) in Bash
Example
Conditional
tomatch='/php-status?full&json'
[[ "$tomatch" =~ '/php-status' ]] && echo match
[[ ! "$tomatch" =~ 'not' ]] && echo does not match
Group Capture
f="helloNico.jpg"
regex=$'[0-9]+_([a-z]+)_[0-9a-z]*'
# double bracket is mandatory
if [[ $f =~ $regex ]]
then
name="${BASH_REMATCH[1]}"
echo "${name}.jpg" # concatenate strings
name="${name}.jpg" # same thing stored in a variable
else
echo "$f doesn't match" >&2 # this could get noisy if there are a lot of non-matching files
fi
Bash Binary operator
When the additional regexp binary operator =~ is used, the string to the right of the operator is considered an extended regular expression and matched accordingly.
The operator has the same precedence as == and !=
The return value is:
- 0 if the string matches the pattern
- 2 if the regular expression is syntactically incorrect
- 1 otherwise.
Others:
- If the shell option nocasematch is enabled, the match is performed without regard to the case of alphabetic characters.
- Any part of the pattern may be quoted to force it to be matched as a string.
- Capturing group are saved in the BASH_REMATCH variable.
Glob
Note that pathname expansion use globbing as well as the control flow structure such as case