根据另一行用另一个替换字符串

Question

I need to write a script, that goes through a bunch of text files and replaces a certain string with another. The other one is located two lines below the certain string. Like this:

some text
this is the first line (helloWorld).
this is the second line.
This is the third line (patternxxx).
more text

And I want this:

some text
this is the first line (helloxxxWorld).
this is the second line.
This is the third line (patternxxx).
more text

I'm under Linux.

Answer 1

awk '
  BEGIN { mr=3 }
  /helloWorld/{ mr=0; gsub("helloWorld","helloxxxWorld");print; };
  mr==2 { gsub("pattern", "patternxxx");}
  mr++
'

test:

$ cat file
some text
this is the first line (helloWorld).
this is the second line.
This is the third line (pattern).
more text
some text
this is the first line (helloWorld).
this is the second line.
this is the second line.
This is the third line (pattern).
more text

$ awk '
  BEGIN { mr=3 }
  /helloWorld/{ mr=0; gsub("helloWorld","helloxxxWorld");print; };
  mr==2 { gsub("pattern", "patternxxx");}
  mr++
' file
some text
this is the first line (helloxxxWorld).
this is the second line.
This is the third line (patternxxx).
more text
some text
this is the first line (helloxxxWorld).
this is the second line.
this is the second line.
This is the third line (pattern).
more text

Answer 2

You can achieve this using sed, see below command. this will permanently make changes in the files.

sed -i 's/helloWorld/helloxxxWorld/g' file1 file2 ...filen

You can loop files one by one also.

 for file in `ls`;
 do
 sed -i 's/helloWorld/helloxxxWorld/g' $file;
 echo "$file completed";
 done

make sure you have backups for the files.

Answer 3

This might work for you (GNU sed):

sed -ri '1N;N;s/(hello)(World.*\n.*\n.*pattern(xxx))/\1\3\2/;P;D' file1 file2 ...

Open a three line window in the file and pattern match on the first and third lines throughout the file.