Yes ed begat sed, but sed works differently. It didn’t replace ed. It did a different job.
Ed loads the file into a buffer which you edit in a random access fashion and then save. Sed collects a list of commands and then streams the file line by line, executing the commands as they match lines. In your example nothing happens until you’ve entered the whole editing script.
You want
sed -i -f -ed is also the precursor of sed, and of some other dozen of commands.
Yes ed begat sed, but sed works differently. It didn’t replace ed. It did a different job.
Ed loads the file into a buffer which you edit in a random access fashion and then save. Sed collects a list of commands and then streams the file line by line, executing the commands as they match lines. In your example nothing happens until you’ve entered the whole editing script.