Question

If I store a long string in a variable and need to test if the string would begin with the letters abc, what would be the most efficient way to test this?

Of course, you could echo the string and pipe it to grep/awk/sed or something like that but isn’t there a more efficient way (which doesn’t require to scan the whole string?)?

Can I use a case statement for this, like e.g.

case $var in
    ^abc) doSomething;;
esac

?

Greets, Oliver

Answer 1

grep doesn’t really need to scan the whole string. Just use echo "$string" | grep '^abc'.

If you really want efficiency, don’t use a shell script.