Mountains of Obfuscation
What would you do?
You have a couple hundred files across several nested folders that contains within them 10000+ obfuscated random and unique user names. You also have a translation file of all of the obfuscated names and new ones you ned to have them replaced with. Some files have all 10000+ obfuscated names in them. Some have none or just a couple.
How would you update all of the files?
Obviously this isn’t a crazy hard problem; there are many ways to solve it. I know how I solved it. I am curious as how YOU would solve it.
Go!
[edit: added clarification]
Two Guys Arguing 
The simplest way first. Read the translation file into memory, create a map from old to new uids. Scan all the folders looking for uids and replace them.
assuming the translation file to be a list of tab-separated pairs of strings:
sed -e ‘s/\([^\t]*\)\t\([^\t]*\)/s\/\1\/\2\/g/g’ translation_file > script
fgrep -rlZ “$(cat translation_file | cut -f 1)” root_dir | xargs -0 sed -i -f script