Re: print specific line (by address) within a block of text

On Wed, 12 Dec 2012 13:13:10 -0500, "Brian J. Murrell"
<[email protected]> wrote:

> Hi,
> 
> So I have some text in which there is a block, delimited by a pattern
> and within that block I want to print a line of text by it's line
> number, relative to the start of the block.  So, given the input:
> 
> a
> b
> c
> d
> e
> f
> g
> h
> 
> i
> j
> k
> l
> m
> 
> within the block starting at 'd' and ending with the blank like I want
> to print the third line, so in this case the line with the "f" on it.
> 
> I am constrained to matching the /d/,/^$/ block by patterns and the
> block could be anywhere in a file so I won't know any line numbers ahead
> of time.
> 
> Extracting the block is simple enough:
> 
> /d/,/^$/
> 
> but once I have that block how can I address into it relative the the
> first line of the block since the block still has it's absolute line
> numbers.
> 
> i.e. /d/,/^$/{
> =
> }
> 
> will print:
> 4
> 5
> 6
> 7
> 8
> 9
> 
> And of course the beginning pattern will not always occur on the same
> line.
> 
> I tried a hold space and replacing the pattern space with the hold space
> but that seemed to retain the original line number addressing once it
> was brought into the pattern space.

Assuming that /d/ *always* starts a block, and omitting some nitpicks
that perhaps are unlikely to be important, you could do

sed -n '/d/{n;n;p;}'

-- 
D.