Check input consists only of numeric characters in shell script

Question

I need to check that the input consists only of numeric characters. I have the code below, but it didn't work properly.

if [[ $1 =~ [0-9] ]]; then
echo "Invalid input"
fi

It should give true only for 678686 not for yy66666.

possible duplicate of [BASH: Test whether string is valid as an integer?](http://stackoverflow.com/questions/2210349/bash-test-whether-string-is-valid-as-an-integer) — tripleee, Sep 04 '13 at 17:35
The reverse test is often more concise: `[[ $1 =~ [^[:digit:]] ]] && echo Invalid` -- if you find one non-digit, it's invalid — glenn jackman, Jun 13 '14 at 11:18

score 2 · Answer 1 · edited Jun 13 '14 at 11:15

2

How about this:-

re='^[0-9]+$'
if ! [[ $Number =~ $re ]] ; then
   echo "error: Invalid input" >&2; exit 1
fi

or

case $Number in
    ''|*[!0-9]*) echo nonnumeric;;
    *) echo numeric;;
esac

edited Jun 13 '14 at 11:15

glenn jackman

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answered Sep 04 '13 at 16:49

Rahul Tripathi

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@tripleee:- Thanks a lot!!! Sometimes you get silly things done just to get an upvote!! ;) – Rahul Tripathi Sep 04 '13 at 17:06

score 1 · Answer 2 · edited May 23 '17 at 12:05

1

Try using start/end anchors with your pattern. If you don't, the match succeeds with a part of a test string. Don't forget that you have to use a pattern matching the complete test string if you follow this suggestion.

if [[ $1 =~ ^[0-9]+$ ]]; then
echo "Invalid input"
fi

Check out this SO post for more details.

edited May 23 '17 at 12:05

Community

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answered Sep 04 '13 at 16:45

collapsar

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@jcrshankar:- Although the above solution works well. I have posted another option as well!!! Have a look :) – Rahul Tripathi Sep 04 '13 at 16:58

Check input consists only of numeric characters in shell script

2 Answers2