sed find and replace multiple lines

supersimha · #1 (**permalink**) 04-03-2009

I am new to linux and would like to modify the contents of a file preferably using a one line. The situation is as follows

<start>
some lines
"I am the string"
"replace string"
more lines here
<end>

In the above example,On encountering "I am the string", the "replace string "should be modified to say "string replaced"

i tried doing the following

sed -e 's/"I am the string"\n"replace string"/"I am the string"\n"string replaced"' myfile.txt

Also how do I make the modifications reflect in the file. its only diplaying at the terminal

supersimha · #2 (**permalink**) 04-03-2009

i have a file say file.txt having following contents

Code:

<tags>match the string</tags>
<tags>match</tags>

Yogesh Sawant · #3 (**permalink**) 04-03-2009

what have you done so far?

ldapswandog · #4 (**permalink**) 04-03-2009

sed only operates on the line contained in its buffer, so to work on multiple lines you need to read more lines into the buffer. Depending on what all you want to do there are flags for read ahead buffer and read behind buffers. Also sed just outputs to screen so you have to redirect the output to a new file, then copy or move the new file to the original file name. I would always make a backup of the original file prior to modifications.

Code:

#sed -e 's/"I am the string"\n"replace string"/"I am the string"\n"string replaced"' 
sed -e '/"I am the string"/N;s/"replace string"/"string replaced"/' myfile.txt > myfile_new.txt

siquadri · #5 (**permalink**) 04-03-2009

Quote:

Originally Posted by supersimha

I am new to linux and would like to modify the contents of a file preferably using a one line. The situation is as follows

<start>
some lines
"I am the string"
"replace string"
more lines here
<end>

In the above example,On encountering "I am the string", the "replace string "should be modified to say "string replaced"

i tried doing the following

sed -e 's/"I am the string"\n"replace string"/"I am the string"\n"string replaced"' myfile.txt

Also how do I make the modifications reflect in the file. its only diplaying at the terminal

Check this

Code:

nawk '$0 ~/findstring/ {print $0;getline;gsub(/replace string/,"replaced string");print}' datafile > datafile1

siquadri · #6 (**permalink**) 04-03-2009

Quote:

Originally Posted by siquadri

Check this

Code:

nawk '$0 ~/findstring/ {print $0;getline;gsub(/replace string/,"replaced string");print}' datafile > datafile1

In place of findstring use I am the String

dennis.jacob · #7 (**permalink**) 04-04-2009

Try this:

Quote:

perl -i -ne 's/I am the string/replace string /; print; ' file

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