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From: aioe on 27 Apr 2010 10:51
Is there an easy way to replace the *previous* newline when a line
contains a regexp match? I suspect awk is the right tool for this, but
I'm not very familiar with awk. It appears to be possible, but very
clumsy, to do this with sed. I know how to do it with an ed script, but
I would like to pipeline.
From: pk on 27 Apr 2010 10:59
aioe wrote:

> Is there an easy way to replace the *previous* newline when a line
> contains a regexp match? I suspect awk is the right tool for this, but
> I'm not very familiar with awk. It appears to be possible, but very
> clumsy, to do this with sed. I know how to do it with an ed script, but
> I would like to pipeline.

Assuming your text does not appear on the very first line, with awk you can
try this:

awk '/pattern/{p="new text"}{print p}{p=$0}END{print p}' file

With sed it's not so difficult (GNU sed syntax):

sed -n '/pattern/{x;s/.*/new text/;x;};x;p;x;h;$p' file

I can't test with ed now but I expect it to be quite simple too.

From: Janis Papanagnou on 27 Apr 2010 11:07
aioe schrieb:
> Is there an easy way to replace the *previous* newline when a line
> contains a regexp match?

You may use printf for output and prepend '\n' to subsequent lines
in case doesn't match.

NR>1 && !/regexp/ { print "" }
{ printf "%s", $0 }
END { print "" }


Janis

> I suspect awk is the right tool for this, but
> I'm not very familiar with awk. It appears to be possible, but very
> clumsy, to do this with sed. I know how to do it with an ed script, but
> I would like to pipeline.
From: aioe on 27 Apr 2010 11:38
On 4/27/2010 8:59 AM, pk wrote:
> aioe wrote:
>
>> Is there an easy way to replace the *previous* newline when a line
>> contains a regexp match? I suspect awk is the right tool for this, but
>> I'm not very familiar with awk. It appears to be possible, but very
>> clumsy, to do this with sed. I know how to do it with an ed script, but
>> I would like to pipeline.
>
> Assuming your text does not appear on the very first line, with awk you can
> try this:
>
> awk '/pattern/{p="new text"}{print p}{p=$0}END{print p}' file
>
> With sed it's not so difficult (GNU sed syntax):
>
> sed -n '/pattern/{x;s/.*/new text/;x;};x;p;x;h;$p' file
>
> I can't test with ed now but I expect it to be quite simple too.
>
Thanks. I didn't make myself clear: I want to replace only the newline
(with space, comma, tab or something) and not the whole previous line.
For example, I would like to join the first two lines by replacing the
newline that precedes [ with a space, but make no other changes, in the
following example:


TCP dell03:4407 mx02.eternal-september.org:nntp ESTABLISHED
2596
[thunderbird.exe]

TCP dell03:netbios-ssn 192.168.2.102:51042 TIME_WAIT 0
TCP dell03:netbios-ssn 192.168.2.102:51041 TIME_WAIT 0

From: aioe on 27 Apr 2010 12:06
On 4/27/2010 9:07 AM, Janis Papanagnou wrote:
> NR>1 && !/regexp/ { print "" }
> { printf "%s", $0 }
> END { print "" }

Thanks. That works, though I would have to spend some time with my awk
book to figure out why.

Suppose I wanted to replace the deleted newlines with tabs?

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