Shell Programming and Scripting

hi All, is there a way in linux to loop thru all variables sourced?
i have a set configs like
A=100
b=200
c=400
i can add the above lines to a file and source - so that $A will be 100 .. like wise

now when i do a cut -c 1-2 file.txt |sort | uniq -c on a file it returns me
A 100
B 50
c 450
d 180

now i want to run thru the config [looking for something like for i in $() - not sure it works with variables]and find the file has any values [A/B/C] has passed the config value
say in this case C has passed 400

please help

---------- Post updated at 08:22 AM ---------- Previous update was at 07:58 AM ----------

think this will work
set -o posix ; set

not entirely sure I understand your requirements, but is this what you're after ??

Code:

 cut -c 1-2 file.txt |sort | uniq -c| awk '$2>400'