Shell Programming and Scripting

I'm looking to match an error code against a list of possible codes and get the nearest match. The code would be a 6 character hexadecimal string.

I have a file of error codes all of which have a specific first 3 characters, however, after that the last 3 characters may be specific or generic as below.

Code:

2120xx
2180xy
2182xy
2193xy
2194xy
21A3xy
21A6xx
21A7xx
21Bxyz
21Cxyz
21D0xy
3073xy
3075xy
30A100
3A0xyy
43Bxxx
43Cyxx
453yxx
463yxx
47Dxxx
47E5xx
47E700
47EC00
BF1x1x
BF2x1x

y and x can be any hex character.

I need to be able to match up to the correct code and the only way I have come up with is rather convoluted. It would involve splitting the original error code into 4 parts, 1st 3 chars then char4, char5 and char6. I would then run a while loop that would read in each error code from the file, split it into the same 4 parts and run comparisons as follows,

Do 1st 3 chars match, if so does char4 match or is it x or y, if so does char5 match or is it x or y, if do does char6 match or is it x or y. If all match then that's the line I need.

I haven't worked out all the detail of that solution but I know I can do it that way. I also know there has to be a better way of doing it.

Can anyone help?

Have you tried using character classes in regular expression?

This one returns the longest match.
It first builds a hashed array s[] with all their shorter variants.
Then it tries to match the full given search, then the shorter variants.

Code:

awk '{
  for (i=6; i>0; i--) s[substr($0,1,i)]
}
END {
  for (i=6; i>0; i--) if ((x=substr(search,1,i)) in s) {print x; exit}
}' search=BF2XXX file-of-error-codes

Code:

BF2

Thank you very much MadeInGermany. That does exactly what I needed and I sort of understand how it works as well. :-)