Dear GNU people:

The GNU sed manual seems to have an error in it. 

In this section:

6.3 Multiline techniques - using D,G,H,N,P to

process multiple lines

You have this example code: 

sed '/./{H;$!d} ; x ; s/^/\nSTART-->/ ; s/$/\n<--END/' input.txt

The input file you give is:

a a a aa aaa

aaaa aaaa aa

aaaa aaa aaa

bbbb bbb bbb

bb bb bbb bb

bbbbbbbb bbb

ccc ccc cccc

cccc ccccc c

cc cc cc cc

and the output promised is:

START-->

a a a aa aaa

aaaa aaaa aa

aaaa aaa aaa

<--END

START-->

bbbb bbb bbb

bb bb bbb bb

bbbbbbbb bbb

<--END

START-->

ccc ccc cccc

cccc ccccc c

cc cc cc cc

<--END

This seemed wrong to me, because as I understood it the '$' symbol should indicate the last line of the file, not merely a blank line, so I executed it on my GNU sed 4.7, and this is the output you get:

START-->

a a a aa aaa

aaaa aaaa aa

aaaa aaa aaa

bbbb bbb bbb

bb bb bbb bb

bbbbbbbb bbb

ccc ccc cccc

cccc ccccc c

cc cc cc cc

<--END

This is what I expected based on other documentation, and it is what happened.

I thought you would want to know.

God bless,

Matthew Hoffman