Bash integer expression expected

Question

To satisfy function requirements I have to retrieve a parameter which is a duty cycle (0-100% in 0.01%).

For test, I wrote something simple like :

#!/bin/bash
#

if [ "$1" -lt 0 ] || [ "$1" -gt 100 ]
then
    echo "bad param"
else
    echo "ok"
fi

I obtain :

root@:~# ./test.sh 11
ok
root@:~# ./test.sh 11,01
./test.sh: line 4: [: 11,01: integer expression expected
./test.sh: line 4: [: 11,01: integer expression expected
bad param

How to realise this kind of test ?

I'm assuming that you're using the , as a decimal point? As your error is telling you, bash only supports integer numbers. — Tom Fenech
– Tom Fenech, Commented Jan 6, 2015 at 14:11
You will have to use bc (see stackoverflow.com/questions/12952427/… for instance) — fredtantini
– fredtantini, Commented Jan 6, 2015 at 14:12

choroba · Accepted Answer · 2015-01-06 15:05:07Z

2

bash can only operate in integer arithmetics. If you need floats, use an external tool like bc:

if (( $( bc <<< "($1 < 0) || ($1 > 100) " ) )) ; then
    ...
fi

I would rather switch to a more powerful language for the whole script, though (like Perl)/

edited Jan 6, 2015 at 15:05

answered Jan 6, 2015 at 14:29

choroba

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2 Comments

Tom Fenech Over a year ago

Any reason for the == within [[, rather than using -eq or ((?

choroba Over a year ago

@TomFenech: Thanks, just a remain of the trial and error :)

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