Check if argument is not Integer

Question

This checks if argument is an integer in Bourne Shell Script:

if [[ $3 =~ ^[0-9]+$ ]] && ((  $3 >= 1 ))

How do I check if argument is not an integer (can consist of integers and alphabets)? So, I guess it's just the complement of above, but I'm not sure how to change it. Where can I find info on what these symbol mean?: =~ ^ + $ &

sampson-chen · Accepted Answer · 2012-11-28 05:19:16Z

3

You can use De Morgan's Law to negate that if condition check as follows:

if [[ ! $3 =~ ^[0-9]+$ ]] || ((  $3 < 1 ))

The ! symbol inside [[...]] means negation.
$3 < 1 is the negation of $3 >= 1

The =~ operator allows use of Regular Expression in an if statement.

The && used here means "Logical AND"

The rest of the symbols ^ + $ are for Regular Expression, which is a topic deserving more reading than I can provide in this answer, but in short:

^: match start of line
+: match one or more (in this context it matches one or more digits)
$: match end of line
Together, ^[0-9]+$ means: Only match a string of nothing but digits.

answered Nov 28, 2012 at 5:19

sampson-chen

47.6k13 gold badges87 silver badges81 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Check if argument is not Integer

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related