Title : Fun tip #3: Split a line using ed
Author: Solène
Date  : 04 December 2018
Tags  : fun-tip unix openbsd68

.Dd December 04, 2018
.Dt "Splitting a line using ed"
In this new article I will explain how to programmaticaly
a line (with a newline) using ed.

We will use commands sent to ed in its stdin to do so. The logic is to
locate the part where to add the newline and if a character need to be

.Bd -literal -offset indent
this is a file
with a too much line in it that should be split
but not this one.

In order to do so, we will format using printf(1) the command list
using a small trick to insert the newline. The command list is the

.Bd -literal -offset indent
/too much line
s/that /that\


This search the first line matching "too much line" and then replaced
"that " by "that\n", the trick is to escape using a backslash so the
substitution command can accept the newline, and at the end we print
the file (replace ,n by w to write it).

The resulting command line is:

.Bd -literal -offset indent
$ printf '/too much line\ns/that /that\\\n\n,n\n' | ed file.txt
> with a too much line in it that should be split
> should be split
> 1     this is a file
2       with a too much line in it that
3       should be split
4       but not this one.
> ?