Regex-related commonly used tasks with shell scripting.

regex_misc.sh

## extract part of a string with grep
echo "12 BBQ ,45 rofl, 89 lol"|grep -P '\d+ (?=rofl)' -o
##  -P means Perl-style regex, -o means match only not the full line

## extract part of a line from every line in a file $FILE
grep -P 'home.*' -o "$FILE" | while read -r line ; do
    echo "$line"
    ## do something with extracted string
    ## e.g. capture part of it into another variable
    VARNAME=$(echo "$line"|grep -P "$DIR.*" -o)
done