Re: What is branch in sed

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Dan Track wrote:
On 8/23/06, Cameron Simpson <cs@xxxxxxxxxx> wrote:
On 23Aug2006 11:52, Dan Track <dan.track@xxxxxxxxx> wrote:
| I've searched and read documents on branching in sed (b) but I still
| can't get my head round it.
|
| Could someone please explain to me how branching works, an example
| would be nice.

It's like goto. Here's an infinite loop:

        :foo
        b foo

Cheers,
--

Hi,

Thanks for the info. With that in mind I have the following example
I'm having trouble unerstanding. Would you be able to help me out with
understanding it? What does the $b in context to the whole file and
executing the lines of code on the file. Also what does $!N mean? And
do I really need P;D?


sed -e '$b
/^Target\[[^]]*\][.0-9]*:.*@[0-9.]*$/ {
$!N
s/^\(Target\[[^]]*\][.0-9]*:.*@\)[0-9.]*\nDirectory\[[^]]*\]:
\(.*\)$/\1\2.example.com/
P;D
}' text_files/mrtg.cfg > text_files/mrtg.cfg.changed

The sed script quoted is heavily based on an example in the "sed FAQ" (http://sed.sourceforge.net/sedfaq4.html#s4.23.2); reading that document is quite useful for people learning sed I think.

Paul.


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