How do I insert a line above specific lines in a file using Vim or Perl?
Question
I'd like to insert the line
<hr />
above every occurrence of a header 2 line in a file - eg, above this pattern
<h2>variable pattern here</h2>
So the above should become
<hr />
<h2>variable pattern here</h2>
How can I do this with Vim, Sed or Perl?
6 answers
solution1
10 2013-01-15 09:52:51
vim way:
cmd :g/<h2>/normal O<hr /> will do the job.
see it here: (I took the example from sudo_O)
solution2
8 ACCPTED 2013-01-15 09:42:48
With sed you could do sed '/<h2>/i <hr />' :
$ cat file
<html>
<h2>variable pattern here</h2>
<h3>not here</h3>
<h2>heading</h2>
<h2>Something</h2>
$ sed '/<h2>/i <hr />' file
<html>
<hr />
<h2>variable pattern here</h2>
<h3>not here</h3>
<hr />
<h2>heading</h2>
<hr />
<h2>Something</h2>
The first part /<h2>/ matches line containing <h2> and the second part uses the i command to insert <hr /> above the matched line.
A nice option with sed is -i this save the changes back to the file instead of printing to stdout but be sure that the changes are correct first.
sed -i '/<h2>/i <hr />' file
solution3
6 2013-01-15 09:54:50
One of the many ways to do that in Vim:
:g/h2/norm O<hr /><CR>
Breakdown:
:g[lobal]acts on every line that match a pattern, see:h :global.h2the pattern we are looking for, it could be made a bit smarter, probably.norm[al]runs a normal mode command, see:h :normal.Oopens a new line above the current line and enters insert mode.<hr />is what you want to insert.We hit
<CR>(<RETURN>) to run the whole thing.
Another way, using a single substitution:
:%s/^\s*<h2/<hr \/>\r&<CR>
Breakdown:
:%s[ubstitute]/performs the substitution on every line of the buffer, see:h :s.^anchors the pattern to the beginning of the line.\\s*matches any number (0 to many) of white space characters. It is not strictly needed if you are sure that all your HTML tags are on column 1.<h2is the pattern we are really looking for.<hr />is what we want to insert.Since we want it to be on its own line, it is followed by a
\\r,and, finally, the matched text,
&.
solution4
3 2013-01-15 09:46:00
use strict;
use warnings;
use Tie::File;
tie my @file, 'example.html'
or die "Unable to tie file: $!";
@file = map { m!<h2>.*</h2>!
? ( "<hr />", $_ )
: $_ } @file;
untie @file;
solution5
3 2013-01-15 10:50:16
Command line solution in Perl.
perl -i~ -p -e'/<h2>/ and $_ = "<hr />\n$_"' your_file.html
Explanation of command line flags:
- -i In-place editing (replace existing file), back-up to your_file.html~
- -p Print each line in the file
- -e Code to execute for each line in the file
If the line contains ( /<h2>/ ) then prepend <hr /> to it (the current line is in $_).
But have you considered if this is the best approach? If you want to add a line above every H2 element, then perhaps you should do that with CSS?
solution6
1 2013-01-15 10:50:51
perl -plne 'print "<hr />" if(/\<h2\>variable pattern here\<\/h2\>/)' your_file
Input file:
> cat temp
<h2>variable pattern here</h2>
1
<h2>variable pattern here</h2>
2
<h2>variable pattern here</h2>
3
4
<h2>variable pattern here</h2>
Now the execution
> perl -plne 'print "<hr />" if(/\<h2\>variable pattern here\<\/h2\>/)' temp
<hr />
<h2>variable pattern here</h2>
1
<hr />
<h2>variable pattern here</h2>
2
<hr />
<h2>variable pattern here</h2>
3
4
<hr />
<h2>variable pattern here</h2>
This will just output to the console. If you want to change it inplace:
perl -pi -lne 'print "<hr />" if(/\<h2\>variable pattern here\<\/h2\>/)' your_file
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