Regex operation to match a white-space not working

Question

I'm trying to make a condition that matches any amount of spaces in a file name $f. But what I have seems to be matching everything?

if [[ $f =~ [[:space:]]* ]]; then
    echo found a space
fi

This matches i-have-no-spaces.jpg as well as i have spaces.jpg

`[[:space:]]*` will always find a match, in any string, as it is "allowed" to match **0** chars due to `*`. — Wiktor Stribiżew, Dec 07 '17 at 08:06
IMHO, I think its more of a `bash` specific usage than a general regex dup (i.e. glob vs regex operator usage) — Inian, Dec 07 '17 at 08:06

score 2 · Accepted Answer · answered Dec 07 '17 at 08:05

2

Don't use *, it means 0 or more matches.

Use

if [[ $f =~ [[:space:]] ]]; then
    echo "found a space"
fi

However in BASH, I suggest to not to use regex for this, just use glob matching with =:

if [[ $f = *[[:space:]]* ]]; then
    echo "found a space"
fi

answered Dec 07 '17 at 08:05

anubhava

1

Thanks, sanity returned! Stupid mistake. I realise now this also works: `$f =~ [[:space:]]+` – sansSpoon Dec 07 '17 at 08:11
1

There is no need to specify a repetition if you only care if there is at least one. – tripleee Dec 07 '17 at 08:28
@tripleee is right, you can just use `$f =~ [[:space:]]+` as written in my answer also. – anubhava Dec 07 '17 at 08:47

1 Answers1