[NTLUG:Discuss] basic Bash question

[Steve Baker]

Lance Simmons wrote:

> Is there a simple way in a bash script to test whether a string is an
> integer?

Hmmm - tricky.

Well, I can think of a kinda-sorta way.

   #!/bin/bash
   XXX=$1
   YYY="WibbleWibble"
   let YYY=$XXX+0 >& /dev/null
   if [[ $YYY == $XXX ]] ; then echo "INTEGER" ; else echo "NOT INTEGER" ; fi

($1 is your string to be tested)

The 'let' statement forces XXX to be treated as an integer.  If it really
is an integer then YYY will be equal to it.  If it's not an integer then
YYY will be left as "WibbleWibble" and YYY and XXX will be different.

The only snag that I know of is that your integer has to have no leading
zeroes.  (My script will say 0123 is not an integer) Also, the string
"WibbleWibble" must never show up as a valid value for your string.

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