How do I test if a variable is a number in Bash?

Question

I just can't figure out how do I make sure an argument passed to my script is a number or not. All I want to do is something like this: test *isnumber* $1 && VAR=$1 || echo "need a number" Any help?

Answer 1

many ways to do this. here's one (could be made more efficient):

function testForNumber() {

result=$(echo -n $1 | grep -E "^[0-9]*$");

if [ "$result" != "" ];

then

echo -n 1;

else

echo -n 0;

fi;

}

isNumber=$(testForNumber $1);

test $isNumber -eq 1 || echo "need a number";

here's a slightly different way:

function testForNumber() {

result=$(echo -n $1 | grep -E "^[0-9]*$");

if [ "$result" != "" ];

then

return 1;

else

return 0;

fi;

}

testForNumber $1;

rtn=$?;

test $rtn -eq 1 || echo "need a number";