Bash shell script multiple tests in while condition

Question

Firstly, yes I have read this:

Bash scripting, multiple conditions in while loop

The answer is probably in that post but I'm failing to see it so I hope someone can help. I want to test for two conditions in my while loop, essentially I want to combine these two tests which are currently nested, one's just a regex, and the second is to test if it is actually a valid date:

while ! [[ "$searchDate" =~ ^[0-9]{1,2}[a-zA-Z]{3}[0-9]{4}$ ]]; do
    read -p "Enter date in format DDmmmYYYY: " searchDate

    while ! (date -d $searchDate); do
        read -p "That date doesn't appear to be valid, try again: " searchDate
    done
done

I feel like I should be able to write something like:

while [[ ! "$searchDate" =~ ^[0-9]{1,2}[a-zA-Z]{3}[0-9]{4}$ ]] || ( ! date -d $searchDate); do
    read -p "There's something funky about that date, try again: " searchDate

but I can't get it to work, I'm not sure if it's my logic that's skewiff, or the way I'm trying to combine the tests (or both!)...

! can only use used immediately after if or while you can't put it into a subshell by itself. — Barmar
– Barmar, Commented Apr 8, 2015 at 17:32
@Barmar you can put ! in front of any (single or multistage) pipeline, including in front of a simple command in a subshell as shown here. It's not specific to if or while in any way. — that other guy
– that other guy, Commented Apr 8, 2015 at 17:38

anubhava · Accepted Answer · 2015-04-08 17:51:02Z

2

You can do

while [[ ! "$searchDate" =~ ^[0-9]{1,2}[a-zA-Z]{3}[0-9]{4}$ ]] || ! date -d $searchDate; do
    read -p "Enter date in format DDmmmYYYY: " searchDate
done

edited Apr 8, 2015 at 17:51

answered Apr 8, 2015 at 17:35

anubhava

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2 Comments

Etan Reisner Over a year ago

There's no reason for the sub-shell around the date command.

anubhava Over a year ago

Thanks, Yes very true, I had also realized that after posting but while debating another answer this change slipped my mind.

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