Comments on: Checking if a variable is a number in ksh

By: Andrew

Andrew — Wed, 15 Apr 2009 17:28:07 +0000

I'm not sure if anyone will read this, but to check if a variable is a number in ksh, it would take 1 expression, there is no reason to add, subtract or do any arithmetic. Example of a script:

G_VAR=$1
if [[ $G_VAR = +([0-9]) ]]; then
print "G_VAR is a number"
else
print "G_VAR is not a number"
fi

By: Mr. KIPS

Mr. KIPS — Fri, 09 Jan 2009 14:31:11 +0000

I wouldn't play with the exit status. Instead, change the arithmetic expression. Use expr $1 +1.

By: nacho_a

nacho_a — Fri, 03 Oct 2008 06:45:49 +0000

What if $1 is 0?
You'll get FALSE!

From expr's man page:

EXIT STATUS
[...]
0 if the expression is neither NULL nor 0
1 if the expression is either NULL or 0

[...]
I'd use "-eq 2" instead of "-ne 0."

Thanks anyway, good tip.