How to remove a tagged block of text in a file?

Question

How can I remove all instances of tagged blocks of text in a file with sed, grep, or another program?

If I have a file which contains:

random
text
// START TEXT
internal
text
// END TEXT
more
random
// START TEXT
asdf
// END TEXT
text

how can I remove all blocks of text within the start/end lines, produce the following?

random
text
more
random
text

score 6 · Accepted Answer · answered May 02 '10 at 10:16

6

sed '\:// START TEXT:,\:// END TEXT:d' file

answered May 02 '10 at 10:16

Dennis Williamson

60,515
14
113
148

score 2 · Answer 2 · answered May 03 '10 at 16:46

The proper way to do this in Perl is with Perl's flip-flop operator

perl -ne'print unless m{^// START TEXT}..m{^// END TEXT}'

x..y in Perl evaluates to true starting with x is true, and ending when y is true. The m{} is another way to write a regular expression match so we don't have to go crazy backslashing all your forward slashes.

score 1 · Answer 3 · answered May 02 '10 at 09:17

#!/usr/bin/nawk -f
BEGIN {
startblock="^/\/\ START TEXT"
endblock="^/\/\ END TEXT"
}
{
        if(! match($0,startblock)) {
                { print }
        }
        else    {
                while ( !match($0,endblock )) {
                        getline;
                }
        }

}

./removeblocks < sometextfile >anothertextfile

score 1 · Answer 4 · answered May 02 '10 at 09:33

1

Perl:

perl -ne '$t=1 if /^\/\/ START TEXT/; print if !$t; $t=0 if /^\/\/ END TEXT/' < sometextfile >anothertextfile

answered May 02 '10 at 09:33

Florian Diesch

1,794
1
11
5

Kyle Brandt · Answer 5 · 2010-05-02T18:45:50.537

1

Simple State Machine:

#!/usr/bin/perl

my $inblock = 0;
while (<>) {
    if (/^\/\/ START TEXT/) {
        $inblock=1;
    } elsif (/^\/\/ END TEXT/) {
        $inblock=0;
    } elsif ( ! $inblock) {
        print;
    }
}

Example Usage:

cat testfile | perl remove_block.pl
random
text
more
random
text

Although Florian's logic is sound I believe with your example, it will print //END TEXT with the following (malformed) input:

random
text
// START TEXT
internal
text
// END TEXT
// END TEXT
more
random
// START TEXT
asdf
// END TEXT
text

edited May 02 '10 at 18:45

answered May 02 '10 at 18:23

Kyle Brandt

82,107
71
302
444

Little bit more tricky question, same sort of line by line state problem: http://serverfault.com/questions/90294/search-and-delete-lines-matching-a-pattern-along-with-comments-in-previous-line-i . Worth reading well you are in the mindset I think. – Kyle Brandt May 02 '10 at 18:39

score 0 · Answer 6 · answered May 02 '10 at 09:10

0

gawk:

BEGIN {
  s = 0
}

s == 1 && $0 ~ /^\/\/ END TEXT$/ {
  s = 0
  next
}

s == 1 {
  next
}

/^\/\/ START TEXT$/ {
  s = 1
  next
}

{
  print
}

answered May 02 '10 at 09:10

Ignacio Vazquez-Abrams

45,019
5
78
84

How to remove a tagged block of text in a file?

6 Answers6