regarding shell scripts arguments

neelendhar · 05-16-2008, 07:24 AM

hi all,

I want to check given command line argument is integer or not in bash script

how to achieve it

for example:

./script -p abc

now valid option for -p is only integer if not script should exit

how to check that $2 is integer or not

blacky_5251 · 05-16-2008, 07:38 AM

Here are some shell statements that should get you started. In your example, replace g with $2.

Code:

$ g="L"
$ typeset -i j
$ j=$g
$ echo $j
0
$ g=2347834
$ j=$g
$ echo $j
2347834
$

Firstly, g has the value of "L" which is clearly not an integer. I then create a new variable - j - using typeset and it will only be able to store integer values. When I assign the value of $g to j, it fails and j has a value of zero.

When $g has a integer value, the assignment to j will work and $g will equal $j.

In your example, replacing $g with $2, you can test that $2 = $j after assigning the value of $2 to j. If $j has the same value as $2, then you know $2 is an integer.

unSpawn · 05-16-2008, 07:41 AM

Use exit value of

Code:

checkNumeric () { typeset -i chkvar; str="$1"; let "foo=$str" 2>/dev/null; }

?

//sorry, didn't see that already got replied to, and way less terse too ;-p

neelendhar · 05-17-2008, 12:09 AM

hi blacky_5251

thanks for reply

solution is ok but what to do in the case he enters '0' as the argument ?

and this is the only solution that we have or any thing else.

blacky_5251 · 05-17-2008, 12:41 AM

There are always other ways to do something in Linux - that is the beauty of it.

Test for zero explicitly before you perform the integer test.

konsolebox · 05-18-2008, 07:53 AM

for (unsigned) integers, i always do this in my codes:

Code:

[[ "${var}" =~ "^[[:digit:]]\+$" ]]

or

Code:

[[ "${var}" =~ ^[[:digit:]]+$ ]]

for your requirement, you can replace ${var} with ${2}

please note that the first one will no longer work in newer versions of bash

example:

Code:

num=1234
if [[ "${num}" =~ "^[[:digit:]]\+$" ]]; then
   echo "unsigned integer"
else
   echo "not an unsigned integer"
fi
[[ "${num}" =~ "^[[:digit:]]\+$" ]] && echo "unsigned integer" || echo "not an unsigned integer"