CODEWITHSUNDEEP
linuxsedawk
user537723
user537723

Reputation: 103

Remove blank lines between patterns

I wish to remove blank lines(new lines, tabs and spaces) in the file with sed or awk, but only if those blank lines are in between two patterns.

lorem lorem PATTERN1

\t

PATTERN2 lorem2 lorem2`

I expect the result below which is a concatenation of 2 lines with both patterns.

lorem lorem PATTERN1PATTERN2 lorem2 lorem2

Upvotes: 2

Views: 1979

Answers (4)

Scrutinizer
Scrutinizer

Reputation: 9946

@user537723: you could try awk:

---improved previous post, so it prints on one line between the patterns---

awk '/PATTERN1/{ORS=x} /PATTERN2/{ORS=RS} ORS || NF' file

Upvotes: 0

Ed Morton
Ed Morton

Reputation: 204638

The GNU awk equivalent of @WilliamPursell's perl script:

awk -v RS='\0' '{print gensub(/(PATTERN1).*(PATTERN2)/,"\\1\\2","g")}' file

Upvotes: 1

potong
potong

Reputation: 58578

This might work for you (GNU sed):

sed -r '/PATTERN1/!b;:a;/PATTERN2/bb;$!{N;ba};:b;s/(PATTERN1.*)[ \t\n]+(.*PATTERN2)/\1\2/;tb' file
  • /PATTERN1/!b just print the line unless it contains the first pattern
  • :a;/PATTERN2/bb;$!{N;ba} read subsequent lines into the pattern space (PS) until the second pattern is encountered
  • :b;s/(PATTERN1.*)[ \t\n]+(.*PATTERN2)/;tb replace all spaces, tabs and newlines between the first and second patterns.

Upvotes: 5

William Pursell
William Pursell

Reputation: 212654

If you just want to delete lines that contain only whitespace between lines that contain PATTERN1 and PATTERN2, just do:

sed '/PATTERN1/,/PATTERN2/{ /^[ \t]*$/d}'

In the sample output you give, it appears that you also want to eliminate the newline that follows PATTERN1, but it's not clear how you want to treat input like:

PATTERN1
non-empty-line

PATTERN2

nor how you want to handle

PATTERN1 non-whitesapce
PATTERN2

Perhaps a clarification of the question is needed. If you really just want to eliminate all whitespace between pattern1 and pattern2, it's probably easiest with:

perl -0777 -pe 's/(pattern1)\s*(pattern2)/$1$2/g'

Upvotes: 1

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