CODEWITHSUNDEEP
bashawksedgrep
Kjetil Treider
Kjetil Treider

Reputation: 5

Bash, Using grep, sed or awk to extract section of text and then match

I have a text file and want to extract all interfaces matching "blue"

random text random text random text 
random text random text 

int 1
    random text
    blue
    random text
    random text
int 2
    random text
    random text
    red
    random text
int 3
    random text
    random text
    random text
    blue
    random text
    random text
int 4
    blue
    random text
int n
    random text
    value
    random text

random text random text random text 
random text random text

Wanted output:

int 1
    blue
int 3
    blue
int 4
    blue
int n
    blue

(notice int 2 is "red" and therefore not displayed)

I've tried: grep "int " -A n file.txt | grep "blue" but that only display lines matching "blue". I want to also show the lines matching "int ". Also the section length can vary so using -A n hasn't been useful.

Upvotes: 0

Views: 480

Answers (4)

123
123

Reputation: 11246

Another sed solution

Will work for multiple blues

sed -n '/^int/{x;/blue/{p;d}};/blue/H' file

Input

random text random text random text
random text random text

int 1
    random text
    blue
    blue
    random text
    random text
int 2
    random text
    random text
    red
    random text
int 3
    random text
    random text
    random text
    blue
    random text
    random text
int 4
    blue
    blue
    blue
    blue
    blue
    random text
int n
    random text
    value
    random text

random text random text random text
random text random text

Output

int 1
    blue
    blue
int 3
    blue
int 4
    blue
    blue
    blue
    blue
    blue

Upvotes: 2

NeronLeVelu
NeronLeVelu

Reputation: 10039

sed '/^int/ h
     /^[[:space:]]*blue/ {x;G;p;}
     d
     ' YourFile
  • Assume there is 1 blue per paragraph and random text is not int or blue line
  • one liner possible (but less explicit)

added (post) constraint

  • paragraphe are all int started, no other (like ext 1, ...)

Explication:

  • keep int line when occur in buffer
  • when blue occur, add last line (exchance buffers, add 2 buffer, so header than blue), print result {x;G;p;} (other action give the same depending of any other interest like H;x;p or H;g;p, in this case this is header destructive but it could be conservative using a s///)
  • delete content (no printing and cycle to next line)

Upvotes: 1

Rambo Ramon
Rambo Ramon

Reputation: 1034

An awk solution could be the following:

awk '/^int/{interface = $0} /blue/{print interface; print $0}' input.txt

It always saves the latest discovered interface. If blue is found, it prints the stored interface and the line containing blue.

Upvotes: 2

josifoski
josifoski

Reputation: 1726

one possible GNU sed solution 

sed -n '/^int\|blue/p' file | sed -r ':a; N; $! ba; s/int \w*\n(int)/\1/g; s/int \w*$//'

output 

int 1  
    blue  
int 3  
    blue  
int 4  
    blue

Upvotes: 1

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