[NTLUG:Discuss] basic Bash question

[Chris Cox]

Lance Simmons wrote:
> I need to test whether a string is an integer.
> 
> I'm tailing a logfile and extracting a string.  99 times out of 100 the
> string is an integer, but sometimes, because of the program that creates
> the logfile, it's not an integer.
> 
> Is there a simple way in a bash script to test whether a string is an
> integer?
> 

a=10
b=String

if expr $a + 1 >/dev/null 2>&1; then
   echo "a in an integer"
fi
if expr $b + 1 >/dev/null 2>&1; then
   echo "b in an integer"
fi