Bash Pattern matching and regular expressions Regex matching
Example
pat='[^0-9]+([0-9]+)'
s='I am a string with some digits 1024'
[[ $s =~ $pat ]] # $pat must be unquoted
echo "${BASH_REMATCH[0]}"
echo "${BASH_REMATCH[1]}"
Output:
I am a string with some digits 1024
1024
Instead of assigning the regex to a variable ($pat) we could also do:
[[ $s =~ [^0-9]+([0-9]+) ]]
Explanation
- The
[[ $s =~ $pat ]]construct performs the regex matching - The captured groups i.e the match results are available in an array named BASH_REMATCH
- The 0th index in the BASH_REMATCH array is the total match
- The i'th index in the BASH_REMATCH array is the i'th captured group, where i = 1, 2, 3 ...
