Find and Replace String in Files

If you just need to perform a simple search and replace, you can use the following syntax:

sed -i 's/string_to_find/string_to_replace/' file1 file2 fileN

Here:

    -i: This flag indicates to sed that your input file is expected to be one of the files specified after the command.
    string_to_find: This is the string that you want to search for in the files.
    string_to_replace: This is the string that you want to replace the string what_to_find within the files.
    file1 file2 fileN: This is the list of files that sed will search and replace.

The following command will search for all strings “Hello” in the welcome.txt file. Then replace it with a new string “Howdy” in the same file.

sed -i 's/Hello/Howdy/g' welcome.txt

You can also create a backup of original file before making changes with -i followed by some extension. For example:

sed -i.backup 's/Hello/Howdy/g' welcome.txt

This will create a file welcome.txt.backup in the current directory with the original file content.