Search and Replace text in one File

To search a string in a file and replace all occurrences of it with a different string use sed:

sed -i 's/string/replace/g' file

With this command all occurrences of the text string in the file file will be replaced with replace.

Search and Replace text in all Files in a directory To

replace all occurrences of a string in all files in a directory recursively use sed in combination with find:

find /directory -type f -exec sed -i 's/search/replace/g' {} \;

This post is only meant as a quick reference for those that sometimes forget the syntax for search and replace (me for example. Especially the combination of sed and find is quite long and I never bothered to remember it as I do not use it that often). If you want to know more about sed read this in depth sed tutorial.