AppleScript to store diff of two files returns an error -

i have 2 simple txt files, a.txt , b.txt.

a.txt

bla 

b.txt

bla bla 

next want store output of diff in variable this:

set my_result shell script "diff a.txt b.txt" 

this seems straightforward, returns following error:

error "1c1,2 < bla \\ no newline @ end of file --- > bla > bla" number 1 

how can avoid this, , store result string?

if files don't match, /usr/bin/diff returns value ≠ 0 , error message in stderr.

applescript throws error if shell script returns non-zero value, have catch error , error message

try     set my_result shell script "diff a.txt b.txt"     -- my_result empty if files match on error e     set my_result e end try