How to replace a string with sed in current and recursive subdirectories

Meet your new friend sed. This amazingly powerful CLI tool lives is available to be totally underused for things like finding and replacing strings in files.

You’ve got two levels of intensity to choose from:

• Non-recursive: Just the files in my current directory.
• Recursive: This directory and all the subdirectories it contains, with maximum prejudice.

Here’s how!

Non-recursive means sed won’t change files in any subdirectories of the current folder.

.
├── index.html        # Change this file
└── blog
    ├── list.html     # Don't change
    └── single.html   # these files

Run this command to search all the files in your current directory and replace a given string. For example, to replace all occurrences of “foo” with “bar”:

sed -i -- 's/foo/bar/g' *

Here’s what each component of the command does:

• -i will change the original, and stands for “in-place.”
• s is for substitute, so we can find and replace.
• foo is the string we’ll be taking away,
• bar is the string we’ll use instead today.
• g as in “global” means “all occurrences, please.”
• * denotes all file types. (No more rhymes. What a tease.)

You can limit the operation to one file type, such as txt, by using a matching pattern:

sed -i -- 's/foo/bar/g' *.txt

You can supplement sed with find to expand your scope to all of the current folder’s subdirectories. This will include any hidden files.

find . -type f -exec sed -i 's/foo/bar/g' {} +

To ignore hidden files (such as .git) you can pass the negation modifier -not -path '*/.*', like this:

find . -type f -not -path '*/.*' -exec sed -i 's/foo/bar/g' {} +

This will exclude any file that has the string /. in its path.

You can also limit this operation to file names that end in a certain extension, like Markdown:

find . -type f -name "*.md" -exec sed -i 's/foo/bar/g' {} +

If you want to update a URL, the / separator in your strings will need escaping. It ends up looking like this…

find . -type f -exec sed -i 
's/https://www.oldurl.com/blog/https://www.newurl.com/blog/g' {} +

You can avoid confusion and mistakes by changing the separator to any non-conflicting character. The character that follows the s will be treated as the separator. In this case, using a , or _ would do. This doesn’t require escaping and is much more readable:

find . -type f -exec sed -i 
's_https://www.oldurl.com/blog_https://www.newurl.com/blog_g' {} +

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