Grep and regex - why am I escaping curly braces?

Question

I\'m deeply puzzled by the way grep seems to parse a regex:

$ echo \"@NS500287\" | grep \'^@NS500[0-9]{3}\'
#nothing
$ echo \"@NS500287\" | grep \'^@NS500[0-         


        

Answer 1

Instead do

echo '@NS500287' | egrep '^@NS500[0-9]{3}'
#                  ^
#                 /
#       notice ---