How to use sed/grep to extract text between two wo

Question

I am trying to output a string that contains everything between two words of a string:

input:

"Here is a String"

output:

"is a"

Using:

sed -n '/Here/,/String/p'

includes the endpoints, but I don't want to include them.

Answer 1

Through GNU awk,

$ echo "Here is a string" | awk -v FS="(Here|string)" '{print $2}'
 is a 

grep with -P(perl-regexp) parameter supports \K, which helps in discarding the previously matched characters. In our case , the previously matched string was Here so it got discarded from the final output.

$ echo "Here is a string" | grep -oP 'Here\K.*(?=string)'
 is a 
$ echo "Here is a string" | grep -oP 'Here\K(?:(?!string).)*'
 is a 

If you want the output to be is a then you could try the below,

$ echo "Here is a string" | grep -oP 'Here\s*\K.*(?=\s+string)'
is a
$ echo "Here is a string" | grep -oP 'Here\s*\K(?:(?!\s+string).)*'
is a

Answer 2

To understand sed command, we have to build it step by step.

Here is your original text

user@linux:~$ echo "Here is a String"
Here is a String
user@linux:~$ 

Let's try to remove Here with substition option in sed

user@linux:~$ echo "Here is a String" | sed 's/Here //'
is a String
user@linux:~$ 

At this point, I believe you would be able to remove String as well

user@linux:~$ echo "Here is a String" | sed 's/String//'
Here is a
user@linux:~$ 

But this is not your desired output.

To combine two sed commands, use -e option

user@linux:~$ echo "Here is a String" | sed -e 's/Here //' -e 's/String//'
is a
user@linux:~$ 

Hope this helps

Answer 3

Simple grep can also support positive & negative look-ahead & look-back: For your case, the command would be:

 echo "Here is a string" | grep -o -P '(?<=Here).*(?=string)'

Answer 4

If you have a long file with many multi-line ocurrences, it is useful to first print number lines:

cat -n file | sed -n '/Here/,/String/p'

Answer 5

This might work for you (GNU sed):

sed '/Here/!d;s//&\n/;s/.*\n//;:a;/String/bb;$!{n;ba};:b;s//\n&/;P;D' file 

This presents each representation of text between two markers (in this instance Here and String) on a newline and preserves newlines within the text.

Answer 6

sed -e 's/Here\(.*\)String/\1/'