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