Question

I am trying to verify that the format of a variable is a number and is at least 10 digits long with leading zeros, inside of an expect script.

In a bash script it would look something like this:

[[ "$var" != +([0-9]) ]] && echo "bad input" && exit
while [[ $(echo -n ${var} | wc -c) -lt 10 ]] ; do var="0${var}" ; done

For the following input:

16

I am trying to achieve the following output:

0000000016

Answer 1

The simplest way to check whether a variable has just digits is to use a regular expression. Expect’s regular expressions are entirely up to the task:

if {![regexp {^\d+$} $var]} {
    puts "bad input"
    exit
}

Padding with zeroes is best done by formatting the value; if you know C’s printf(), you’ll recognize the format:

set var [format "%010d" $var]