Search and Replace in Multiple Files

25 July, 2015

$ sed -i "s/pattern/replacement/g" FILES

The Story

Last semester I had to write a static website by hand with no templating resulting in a lot of duplicated code across multiple pages. I had already finished most of the project when I realised that the main page of the project should be named index.html instead of home.html. I renamed the file, but that left me with countless references to “home.html” that needed to be changed, and I wanted to change them all at once. Enter sed.

sed allows the user to write programs which operate on streams of text. It is run using the syntax

$ sed OPTIONS.. [SCRIPT] [FILENAME..]

To search and replace using sed we use the s command of the form s/regex/replacement/flags. Our sed script would become s/home\.html/index.html/g. The . needs to be escaped because . on its own matches any character in regex. The g flag means to replace every occurrence of the pattern, instead of just the first.

By default, sed will only write the altered text to stdout, so we need to use the -i flag to make the alterations inside the source file.

The final command is now

$ sed -i "s/home\.html/index.html/g" *.html

which will apply the sed program to all the HTML files in the directory. Easy!