Bash - Regex

Multilingual Regular Expression Syntax (Pattern) in Bash

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 (as in regex(3)).

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.

Example:

• First

f="helloNico.jpg"
regex=$'[0-9]+_([a-z]+)_[0-9a-z]*'

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

• http://stackoverflow.com/questions/1891797/capturing-groups-from-a-grep-regex