CODEWITHSUNDEEP
regexawksed
geekinthesticks
geekinthesticks

Reputation: 33

Remove One or More Blank Lines After a String

#+BEGIN_HTML

some html
more html

#+END_HTML

I have some files that contain text like the above. I want to remove any blank lines following #+BEGIN_HTML, so I end up with:

#+BEGIN_HTML
some html
more html

#+END_HTML

The file contains blank lines in other places, which I don't want to remove. I am struggling to come up with a regexp that will let me do this.

Upvotes: 1

Views: 81

Answers (6)

cuonglm
cuonglm

Reputation: 2806

Try:

sed -e ':1' -e '/#+BEGIN_HTML/{$!N;/\n$/s///;t1}'

Upvotes: 0

Tom Fenech
Tom Fenech

Reputation: 74596

Here's another one using awk:

awk 'f{if(!NF)next;f=0}/#\+BEGIN_HTML/{f=1}1' file

f is set to 1 when the pattern is matched. When f is 1, blank lines (where NF is 0) are skipped. f is set to 0 when the line is no longer blank.

Testing it out:

$ cat file
#+BEGIN_HTML



some html
more html

#+END_HTML
$ awk 'f{if(!NF)next;f=0}/#\+BEGIN_HTML/{f=1}1' file
#+BEGIN_HTML
some html
more html

#+END_HTML

Upvotes: 0

Jotne
Jotne

Reputation: 41446

Here is an awk solution:

awk '!NF && f {next} 1; NF {f=0} /#\+BEGIN_HTML/ {f=1}' file
#+BEGIN_HTML
some html
more html

#+END_HTML

Or as Jidder sugested:

awk '!NF&&f{next}{f=/#\+BEGIN_HTML/}1' file

Upvotes: 1

anubhava
anubhava

Reputation: 784928

Using awk:

awk '/#\+BEGIN_HTML/{print; skip=1; next} skip {if (!NF) next; else skip=0} 1' file
#+BEGIN_HTML
some html
more html

#+END_HTML

Upvotes: 0

Avinash Raj
Avinash Raj

Reputation: 174696

Through perl,

$ perl -0777pe 's/(?<=^#\+BEGIN_HTML\n)\n+//g' file
#+BEGIN_HTML
some html
more html

#+END_HTML

OR

perl -00pe 's/(?<=^#\+BEGIN_HTML\n)\n+//g' file

Upvotes: 0

jaypal singh
jaypal singh

Reputation: 77075

Using sed: 

sed ':a;/^#+BEGIN_HTML/{N;/\n./!s/\n.*//;ta}' file

Create a label a. For lines that start with #+BEGIN_HTML, append the next line to pattern space. Substitute everything from newline to the end of next line unless it is not a line that is blank. Repeat the loop if the substitution modified the pattern space.

Upvotes: 1

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