Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!bbn!bbn.com!jgrace
From: jgrace@bbn.com (Joe Grace)
Newsgroups: comp.editors
Subject: Re: SED Question
Summary: sed is broken
Keywords: sed
Message-ID: <38564@bbn.COM>
Date: 12 Apr 89 00:11:35 GMT
References: <2360001@hpcuhc.HP.COM>
Sender: news@bbn.COM
Reply-To: jgrace@BBN.COM (Joe Grace)
Organization: Bolt Beranek and Newman Inc., Cambridge MA
Lines: 47

In article <2360001@hpcuhc.HP.COM> smaxwell@hpcuhc.HP.COM (Susan Maxwell) writes:
>
>Got a sed question for you:  I'm creating a sed filter to mask out and
>delete unwanted characters in a trace file.  I'm having trouble with this
>configuration:
>
>        LINE I:    PROMPT>
>        LINE I+1:  >
>        LINE I+2:  <
>
>Whenever I see this series, I want to delete ALL THREE lines.  I can't
>create a pattern /PROMPT\>\\n\>\\n\</d   as far as I can tell, because
>sed won't allow patterns to span lines.  Is there a way to do this, without
>resorting to awk or ed?   
>
>Susan Maxwell

Yes, there is a way to get sed to do this, but you have to be
wary of sed's shortcomings.

Try:
----
#! /bin/sh

(cat trace.out;  echo "SomeUniqueID")  \
| sed  \
    -e '/^PROMPT>$/{'  \
      -e 'N'  \
      -e '/\nSomeUniqueID$/{;s@\nSomeUniqueID$@@;q;}'  \
      -e 'N'  \
      -e '/\nSomeUniqueID$/{;s@\nSomeUniqueID$@@;q;}'  \
      -e '/^PROMPT>\n>\n<$/d'  \
    -e '}'  \
    -e '/^SomeUniqueID$/d'

If sed had a way of handling an EOF without quitting, the
SomeUniqueID would be unnecessary.  As sed is, the SomeUniqueID
is used to avoid losing lines which start out the same as your
pattern but which do not fully match your pattern --- and which
you therefore want to keep.

Cheers,

= Joe =
Joe Grace
ARPA: jgrace@bbn.com
UUCP: {harvard,husc6,decvax,etc.}!bbn!jgrace