How to match regexp with ash?

Question

Following code works for bash but now i need it for busybox ash , which apparrently does not have "=~"

keyword="^Cookie: (.*)$"
if [[ $line =~ $keyword ]]
then
bla bla
fi

Is there a suitable replacement ?

Sorry if this is SuperUser question, could not decide.

Edit: There is also no grep,sed,awk etc. I need pure ash.

Technicality

Wow, no POSIX. Just out of curiosity, what system are you running on? – Adria

Answer 1

For this particular regex you might get away with a parameter expansion hack:

if [ "$line" = "Cookie: ${line#Cookie: }" ]; then
    echo a
fi

Or a pattern matching notation + case hack:

case "$line" in
    "Cookie: "*)
        echo a
    ;;
    *)
    ;;
esac

However those solutions are strictly less powerful than regexes because they have no real Kleene star * (only .*) and you should really get some more powerful tools (a real programming language like Python?) installed on that system or you will suffer.

Adria

Thanks this works. As you say it is very limited though. It is a router with very little space cant install perl or python. Might try C. – Technicality

Answer 2

What worked for me was using Busy Box's implementations for grep and wc:

MATCHES=`echo "$BRANCH" | grep -iE '^(master|release)' | wc -l`
if [ $MATCHES -eq 0 ]; then
 echo 'Not on master or release branch'
fi

Pollywog

Note that it is better to work with -q option, e.g.: if $(echo "$BRANCH" | grep -qiE '^(master|release)'); then – Brann

Answer 3

Busybox comes with an expr applet which can do regex matching (anchored to the beginning of a string). If the regex matches, its return code will be 0. Example:

 # expr "abc" : "[ab]*"
 # echo $?
 0
 # expr "abc" : "[d]*"
 # echo $?
 1

Claypan

Answer 4

You can use expr.

Define the function:

match() {
    local text="${1}";
    local rexp="${2}";
    # NOTE: expr regex is anchored with '^'
    expr "${text}" : "${rexp}" > /dev/null;
}

Test the function:

if match "string" "s"; then
    echo "true"
fi;

Demaggio