sed & awk, 2nd Edition

Hold That Line

The pattern space is a buffer that contains the current input line. There is also a set-aside buffer called the hold space. The contents of the pattern space can be copied to the hold space and the contents of the hold space can be copied to the pattern space. A group of commands allows you to move data between the hold space and the pattern space. The hold space is used for temporary storage, and that’s it. Individual commands can’t address the hold space or alter its contents.

The most frequent use of the hold space is to have it retain a duplicate of the current input line while you change the original in the pattern space. The commands that affect the pattern space are:

Command	Abbreviation	Function
Hold	h or H	Copy or append contents of pattern space to hold space.
Get	g or G	Copy or append contents of hold space to pattern space.
Exchange	x	Swap contents of hold space and pattern space.

Each of these commands can take an address that specifies a single line or a range of lines. The hold (h,H) commands move data into the hold space and the get (g,G) commands move data from the hold space back into the pattern space. The difference between the lowercase and uppercase versions of the same command is that the lowercase command overwrites the contents of the target buffer, while the uppercase command appends to the buffer’s existing contents.

The hold command replaces the contents of the hold space with the contents of the pattern space. The get command replaces the contents ...