Meaning of ",$d" in replacement part of sed command

Question

I came across this command in a project I am working on:

sed -i '/regex/,$d' file

I don't understand how the ,$d part works. If I omit any part of ,$d I get errors. In my tests it looks like it replaces the matching line and anything after it with nothing. Example:

File with contents:

first line 
second line regex
third line
fourth line

Comes out as after running that command:

first line

I couldn't find any documentation in the man page that explains this, though I could have easily missed it. The man page is hard for me to parse...

This is example was tested with GNU Sed v 4.2.2.

Answer 1

This is not a replacement command; the sed substitute or replace command looks like s/from/to/.

The general form of a sed script is a sequence of commands - typically a single letter, but some of them take arguments, like the s command above - with an optional address expression before each. You are looking at a d (delete line) command preceded by the address expression /regex/,$

The address range specifies lines from the first regex match through to the end of the file ($ in this context specifies the last line) and the action d deletes the specified lines.

Although many people only ever encounter simple sed scripts which use just the s command, this behavior will be described in any basic introduction to sed, as well as in the man page.