How to replace letters with numbers in a string

[wsadowy1]

I'm trying to convert a long hexadecimal number (md5) to decimal.
Unfortunately md5_number = tonumber(md5_string,16) does not seem to work, perhaps due to the number's length.
So I thought I would replace respective letters in the md5 string with numbers. "a" to 10, "b" to 11 ... "f" to 16. The correctness of the final number does not play a role as I only need it to compare two neighboring events using "delta" function, so I need decimal numbers for that purpose.
Unfortunately I am unable to do it using replace or rex in sed mode.
Example md5 hash: 6c17f73c47a12dcf494cd95e3e8bd490
Any help will be appreciated.

[koshyk · Accepted solution]

A crude way, but should work
(splitting first 8 characters and converting to number and then next 8 chars and converting and then concatenating both)

| stats count as echo | eval decimal = tostring(tonumber(substr("D431F2404CA13E22594E5C8B04D3BBB8",1,8),16)) + tostring(tonumber(substr("D431F2404CA13E22594E5C8B04D3BBB8",9,8),16))| fields decimal

[wsadowy1]

Thanks!
I actually managed to achieve my goal by writing a rather lenghty nested replace function:
tonumber(replace(replace(replace(replace(replace(replace(log_msg_hash,"a","10"),"b","11"),"c","12"),"d","13"),"e","14"),"f","15"))
It doesn't calculate the number properly but it does create SOME decimal number which primarly was my goal.

[paramagurukarth]

Try creating a custom command and implement your own logic in python to achieve your requirement
http://docs.splunk.com/Documentation/Splunk/6.0.8/AdvancedDev/SearchScripts

[wsadowy1]

I don't think I would be able to do it since I'm using Web Splunk and have no access to commands.conf. I'm pretty sure one can do it with rex sed, but my level of expertise is not sufficient and I couldn't find any examples that would suit my need.