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Delete a block of text delimited by blank lines when pattern is found

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Top Forums Shell Programming and Scripting Delete a block of text delimited by blank lines when pattern is found
# 8  
Old 12-15-2007
Or even:

Code:
awk '!/pattern/' ORS="\n\n" RS= file

You need ORS to restore the blank lines between the blocks.

But it's quite possible to get (not GNU Awk) the "line too long" error ...
# 9  
Old 12-15-2007
Quote:
Originally Posted by gleu
I don't quite understand the above bit of code about the Set-Aside buffer (but I'll look it up later ...unless you or someone wants to explain for the benefit of others).

Sure,
check Bruce Barnett's Sed - An Introduction and Tutorial - Flow Control
# 10  
Old 12-15-2007
Hi.

A perl script doesn't usually need to worry about line length, and telling perl about the definition of a block (I call it a visual paragraph) is simple:
Code:
#!/usr/bin/perl

# @(#) p1       Demonstrate visual paragraph skip if pattern found.

use warnings;
use strict;

my($debug);
$debug = 0;
$debug = 1;

my($lines) = 0;
my($pattern) = shift || die "usage: $0 pattern [files]\n";

$/ = "";        # block separator: any sequence of two or more newlines.

while ( <> ) {
        $lines++;
        print if !/$pattern/xms;        # always use xms on matches
}

print STDERR " ( Blocks read: $lines )\n";

exit(0);

Using the block test file of radoulov and ghostdog74 as "data1" produces:
Code:
% ./p1 pattern data1
block2
block2
block2
block2

 ( Blocks read: 3 )

Best wishes ... cheers, drl
# 11  
Old 12-15-2007
Quote:
Originally Posted by radoulov
Sure,
check Bruce Barnett's Sed - An Introduction and Tutorial - Flow Control
Thanks.
I've also been reading the relevant bits in Sed & Awk by Dale Dougherty and Arnold Robbins (O'Reilly). I understand the code now.
# 12  
Old 12-15-2007
Quote:
Originally Posted by ghostdog74
Code:
...
# awk 'BEGIN{RS=""}/pattern/{next}1' file
block2
block2
block2
block2

The awk code looks straightforward but I could not get that code to work
Code:
gawk 'BEGIN {RS=""}/pattern/{next}' myfile

(I took out the 1 after next because I thought it was a typo... but in any case with or without the 1, the code gives me no output at all :-(
Last edited by gleu; 12-15-2007 at 06:19 PM.. Reason: missing closing apostrophe
# 13  
Old 12-15-2007
Quote:
Originally Posted by radoulov
Or even:

Code:
awk '!/pattern/' ORS="\n\n" RS= file

You need ORS to restore the blank lines between the blocks.

But it's quite possible to get (not GNU Awk) the "line too long" error ...

I can't get your version (nor ghostdog74) to output anything.
gawk '!/pattern/' ORS="\n\n" RS= myfile
Strange
... but at least the sed version works a treat!
# 14  
Old 12-15-2007
Quote:
Originally Posted by gleu
I can't get your version (nor ghostdog74) to output anything.
gawk '!/pattern/' ORS="\n\n" RS= myfile
Post a sample from your (real) file.
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