As a software programmer you often have to search and replace a specific string in multiple files because of a refactoring or just improving a variable or function name.

Normally you can use your IDE or your editor for this. But in bigger codebases with thousand or million lines of code it can be very slow. Neither do IDEs work with remote SSH-sessions. In such situations the command-line is pretty handy. It is available everywhere and it is fast.

The following command replaces old with new in all *.go files in the current directory:

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# bsd tools, e.g. MacOS
find . -iname '*.go' | xargs sed -i '' -e 's/old/new/g'

# gnu tools, e.g. Linux
find . -iname '*.go' | xargs sed -i -e 's/old/new/g'

I use this often in combination with git. First i commit my latest changes, so i have a clear state. Then i issue the above find-sed command. Afterwards i check the changes in the files with git diff. If i do not like them, reverting is possible with git reset.