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Sometimes you need to quickly replace a line of text across your documents. While you could open the documents and hand-edit them one-by-one, the easier solution is to use a Terminal command called “sed” that allows you to specify a string of text that should be substituted by another. With this command, you can easily find and replace occurrences of words a document, automatically. Continue reading, and we’ll show you how to put this powerful command to good use.
Substitute All Occurrences of Word in a Single File
If you have a single file in which you wish to replace all occurrences of a single word with another, you can easily do it using the following command:
sed 's/FindThisWord/ReplaceWithThisWord/g' file.txt
Replace the word “FindThisWord” in the above command with the word you wish to be replaced, and substitute the word “ReplaceWithThisWord” in the above command with the word you wish to replace the word with.
Apple is awesome!
We could run the following command to replace “Apple” in the above text document with “MacLife” instead:
sed 's/Apple/MacLife/g' sample.txt
The edited document will be printed to the screen for you to see.
Writing Changes to the File
All is good, but the above command doesn’t save the changes to the original file, it only prints the updated file to the screen. To write the changes back to an output file, you’ll use the following command instead:
sed -n 's/FindthisWord/ReplaceWithThisWord/gpw output.txt' file.txt
So, if we continue with the same example above, replacing “Apple” in the sentence with “MacLife,” then use the following command:
sed -n 's/Apple/MacLife/gpw output.txt' sample.txt
This will cause sed to not only change the file and print it to the screen, but will also cause the changes to be written back to a file called “output.txt” (you can change this name inside of the replacement string command.
Cory Bohon is a freelance technology writer, indie Mac and iOS developer, and amateur photographer. Follow this article's author on Twitter.