Living in the Shell #14; sed (Text Stream Editor) (Part 1)

sed 🖊️

Edits streams by applying commonly used modifications.

Add a new line a & i

cat some-file.txt | sed '3a This is a new line after the 3rd line' 
cat some-file.txt | sed '3i This is a new line before the 3rd line'

Append a new line to the end $a

cat some-file.txt | sed '$a Now, this is the last line'

Prepend a new line to the beginning 1i

cat some-file.txt | sed '1i Now, this is the first line'

Replace one or more lines c

cat some-file.txt | sed '1-3c BOOM'

Replaces lines 1 through 3, with 'BOOM'.

Delete one or more lines d

cat some-file.txt | sed '1-3d'

Deletes lines 1 through 3.

Comments

[Brian Richardson]

These were some uses of sed I wasn't aware of, thanks. Still, the true power of sed must be acknowledged to be its replacement capabilities using regular expressions. For example, search and replace within a directory:

find . -name \*.js -exec cat {} | sed -e 's#replaceme#replacement#g' > output.txt

[Babak K. Shandiz]

That's right. I'll cover some use cases of string/pattern substitution in Part 2.