Linux tutorial on replacing strings using sed command

To replace a string, we need to use the following format.

$ sed s/replacement target string/replacement string/file name

In the following we replace the string "sample.txt" written as "appleorangemelon".

$ sed s/orange/ORANGE/ sample.txt

The execution result is

appleORANGEmelon

Replace and output a string.

In addition, as shown below, you can also get the same result by connecting the sed command with "|" after the cat command.

$ cat sample.txt | sed s/apple/APPLE/

Note that the sed command only replaces the string and outputs it, but does not rewrite the actual file contents.

If you want to keep the replaced content in text, use the redirection ">".

Options used by sed command

Use of sed command

Replace all lines

In the format described previously, even if there are strings matching multiple replacement target strings in one line, only the first matching string is replaced.

So, to replace all matching strings, do:

$ sed -es /apple/APPLE/g sample.txt

The execution result is

APPLEorangemelonAPPLE

Replace the beginning and end of a line

$ sed -e "s/^apple/APPLE/" sample.txt
$ sed -e "s/apple\$/APPLE/" sample.txt

If you want to replace multiple substrings, you can specify multiple scripts.

$ sed -e "s/apple/APPLE/" -e "s/orange/ORANGE/" sample.txt

Deleting a row

Specify "d" to delete the specified line. For example, to delete the second line, enter "2d".

$ sed -e '2d' sample.txt

In addition, you can also delete multiple lines. The following is to delete lines 1 to 3.

$ sed -e '1,3d' sample2.txt