looking for math

[soldier.coder]

I'm looking for code that will do some operation on a file and give me
a number that is unique to that file. if I happen to come across same
file somewhere else and the contents are the same, the same number
should be produced.

First what is that called, and anyplace i can see code that does that?

 

[Anton Zeuchert]

How about http://ruby-doc.org/ruby-1.9/classes/Digest.html?

 

[Fabio Cevasco]

[Note: parts of this message were removed to make it a legal post.]

Perhaps you mean creating checksums or MD5 digests?

The code is simple, assume there's a "README.textile" file in the current
directory; just launch IRB and do the following:
____
ruby-1.9.2-p136 :001 > require "digest"
=> true
ruby-1.9.2-p136 :002 > Digest::MD5.file("README.textile").to_s
=> "fd4964756811f1590cc13efb7ac7895a"
____

For more information, see the Digest library:
http://ruby-doc.org/stdlib/libdoc/digest/rdoc/index.html

Hope it helps,

Fabio Cevasco
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On Sun, Feb 6, 2011 at 6:30 PM, soldier.coder <

 

[Brian Candler]

soldier.coder wrote in post #979906:

I'm looking for code that will do some operation on a file and give me
a number that is unique to that file. if I happen to come across same
file somewhere else and the contents are the same, the same number
should be produced.

First what is that called

It's called a "cryptographic hash".
http://en.wikipedia.org/wiki/Cryptographic_hash_function