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Check if variable is a number

Terminal - Check if variable is a number
if [ "$testnum" -eq "$testnum" 2>/dev/null ]; then echo It is numeric; fi
2009-10-09 14:57:27
User: jgc
Functions: echo
Check if variable is a number

Using the standard numeric comparison but suppressing the STDERR output acts as the simplest way to check a value is numeric. See sample output for some examples.


There is 1 alternative - vote for the best!

Terminal - Alternatives
if [[ "$1" =~ ^[0-9]+$ ]]; then echo "Is a number"; fi
(($1 > 0)) && echo "var is a number"
2013-03-22 01:15:00
User: khayyam
Functions: echo

calculate if "$1" is a number ... decimals included :)

echo $X | egrep "^[0-9]+$"

Know a better way?

If you can do better, submit your command here.

What others think

Try this.

export testnum=" " # a space

This will still echo out It is numeric.

Comment by uberwrensch 355 weeks and 1 day ago

Accepting space is a feature, since the Bash shell usually assumes null values are zero for arithmetic purposes. If that's not your purpose, then yeah this check isn't appropriate.

Comment by ashawley 355 weeks ago

if you're talking about bash, and not plain sh:

[[ $testnum =~ ^[0-9]+$ ]] && echo is a number

yes -- that's a real regex. Dont put slashes around it (took me a while to realise that when I first tried this a few months ago!)

Comment by sitaram 354 weeks and 6 days ago

@sitaram: make that a command and I'll vote for it

Comment by ashawley 354 weeks and 4 days ago

Your point of view

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