Tcl regexp: How to check if variable contains number?

Question

Below is my tcl script for checking if there is any 0-9 number find in the variable.

    set a "abc"

    if {[ regexp {[0-9]*} $a ]} {
       puts "Found number in $a"
    } else {
       puts "Doesn't find number in $a"
    }

But when I run it, it reports "Found number in abc".

Answer 1

That's because you are using a regular expression that means "match 0 or more numbers". The string abc matches 0 numbers, so you get a positive result. Just remove the * ("0 or more") and it should work as expected:

set a "a2bc"

if {[ regexp {[0-9]} $a ]} {
        puts "Found number in $a"
} else {
        puts "Doesn't find number in $a"
}

Answer 2

In a regular expression, * means "zero or more of the previously specified character or class". So you are looking for any string with zero or more numerical characters. Which matches everything.

Answer 3

You can use glob-style patterns to solve this as well without needing the power of regular expressions:

if {[string match {*[0-9]*} $a]} { ...

See string match documentation.