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From: mnc@m10ux.UUCP (Michael Condict)
Newsgroups: comp.unix.wizards
Subject: Re: embedded newlines in shell variable?
Message-ID: <323@m10ux.UUCP>
Date: Thu, 13-Aug-87 15:26:01 EDT
Article-I.D.: m10ux.323
Posted: Thu Aug 13 15:26:01 1987
Date-Received: Sat, 15-Aug-87 14:28:25 EDT
References: <228@cjsa.UUCP>
Organization: AT&T Bell Labs, Murray Hill
Lines: 47
Keywords: sed sh shell
Summary: How to get new lines in sed command

In article <228@cjsa.UUCP>, jeff@cjsa.UUCP writes:
> I have been attempting to construct a 'sed' command line script and load it
> into a shell variable (called ACTION) for later use within a bourne shell
> script.  All goes well until I need sed to append new text to the end of the
> input data.  To work, sed's append command ( a\ ) requires newlines to be
> embedded as follows:
> 			'$a\
> 			NEW LINE OF MATERIAL'
> 
>  . . .

The following dialog worked for me, using /bin/sh.  Note that I use explicit
new lines, rather than the "\n" notation.  Also note that you should not
escape a "$" character that is inside single quotes -- the escape is not
interpreted specially there and will leave a literal escape character in
your string, which sed will barf on:

$ cmd='$a\
> dog'
$ echo 'hello
> goodbye' | sed -e "$cmd"

The sed command appends "dog" after the last line of input, which in this
case produces:

hello
goodbye
dog

as output.  This is on System V Rel. 2, by the way.

I think your problem is that you are mistaken about the meaning of "\n"
in shell strings.  It is not transformed on input to a newline character.
The echo command will transform it to a new line on output, but other
commands may or may not process it as a new line.  To prove this to yourself,
try:

	$ str='a\nb'
	$ cc "$str".c

Cc will complain that it cannot open the file "a\nb.c", thus indicating that
the "\n" sequence was inserted unchanged into the string and was left
unchanged by the shell when it fed the string to cc.
-- 
Michael Condict		{ihnp4|vax135|cuae2}!m10ux!mnc
AT&T Bell Labs		(201)582-5911    MH 3B-416
Murray Hill, NJ