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From: Jack Shown on 6 Oct 2009 19:17
Is it possible using sed, awk, perl or anything else to search a file
for a regex and if that line is followed by another regex then display
both lines otherwise display only the first line?

For example, suppose I grep a file for "Ultra" but want the following
line also output if the following line contains "fixed".

Thanks.
From: Ben Bacarisse on 6 Oct 2009 19:49
Jack Shown <jackshown(a)gmail.com> writes:

> Is it possible using sed, awk, perl or anything else to search a file
> for a regex and if that line is followed by another regex then display
> both lines otherwise display only the first line?
>
> For example, suppose I grep a file for "Ultra" but want the following
> line also output if the following line contains "fixed".

Slightly clunky:

grep -A1 Ultra <data | grep 'Ultra\|fixed'

but it does what you ask and it will go wrong if either regex matches
grep's group separator (--).

--
Ben.
From: Janis Papanagnou on 6 Oct 2009 19:50
Jack Shown wrote:
> Is it possible using sed, awk, perl or anything else to search a file
> for a regex and if that line is followed by another regex then display
> both lines otherwise display only the first line?

awk '
/pattern1/ {print; flag=1; next}
/pattern2/ && flag {print}
{flag=0}
'

Janis

>
> For example, suppose I grep a file for "Ultra" but want the following
> line also output if the following line contains "fixed".
>
> Thanks.
From: sharma__r on 6 Oct 2009 20:20
On Oct 7, 4:17 am, Jack Shown <jacksh...(a)gmail.com> wrote:
> Is it possible using sed, awk, perl or anything else to search a file
> for a regex and if that line is followed by another regex then display
> both lines otherwise display only the first line?
>
> For example, suppose I grep a file for "Ultra" but want the following
> line also output if the following line contains "fixed".
>
> Thanks.

One way to do it is (using "sed"):

sed -e '
/Ultra/\!d
n
/fixed/\!d
' yourfile


-- Rakesh
From: Grant on 6 Oct 2009 20:23
On Wed, 07 Oct 2009 01:50:16 +0200, Janis Papanagnou <janis_papanagnou(a)hotmail.com> wrote:

>Jack Shown wrote:
>> Is it possible using sed, awk, perl or anything else to search a file
>> for a regex and if that line is followed by another regex then display
>> both lines otherwise display only the first line?
>
> awk '
> /pattern1/ {print; flag=1; next}
> /pattern2/ && flag {print}
> {flag=0}
> '

Is it faster if you swapped /pattern2/ and flag? (does (g)awk do
short circuit logic?)

Grant.
--
http://bugsplatter.id.au
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