converting caps in shell scripts

[Tim]

Hi All

Can anyone suggest a method to convert capitals to lower case in a shell
script.

I have a radius log that I am trying to convert the usernames to all lower
case characters.  I am picking up the usernames using a test function which
is failing because  [ Able = able ] is not performing the query, as one
would expect.  The rest of the script I am using is written as a shell
script and I don't really want to have to rewrite it in perl at present.  I
have done a man sh, man test  etc but can't see anything in there that I can
use.  Do I need to re write it in perl?

TIA

Tim