unix command to get lines from in between first and last occurence of a word and write to a file

Question

I want a unix command to find the lines between first & last occurence of a word

For example:

let's imagine we have 1000 lines. Tenth line contains word "stackoverflow", thirty fifth line also contains word "stackoverflow".

I want to print lines between 10 and 35 and write it to a new file.

Answer 1

You can make it in two steps. The basic idea is to:

1) get the line number of the first and last match.

2) print the range of lines in between these range.

$ read first last <<< $(grep -n stackoverflow your_file | awk -F: 'NR==1 {printf "%d ", $1}; END{print $1}')
$ awk -v f=$first -v l=$last 'NR>=f && NR<=l' your_file

Explanation

• read first last reads two values and stores them in $first and $last.
• grep -n stackoverflow your_file greps and shows the output like this: number_of_line:output
• awk -F: 'NR==1 {printf "%d ", $1}; END{print $1}') prints the number of line of the first and last match of stackoverflow in the file.

And

• awk -v f=$first -v l=$last 'NR>=f && NR<=l' your_file prints all lines from $first line number till $last line number.

Test

$ cat a
here we
have some text
stackoverflow

and other things
bla
bla
bla bla
stackoverflow
and whatever else
stackoverflow
to make more fun
blablabla

$ read first last <<< $(grep -n stackoverflow a | awk -F: 'NR==1 {printf "%d ", $1}; END{print $1}')
$ awk -v f=$first -v l=$last 'NR>=f && NR<=l' a
stackoverflow

and other things
bla
bla
bla bla
stackoverflow
and whatever else
stackoverflow

By steps:

$ grep -n stackoverflow a
3:stackoverflow
9:stackoverflow
11:stackoverflow

$ grep -n stackoverflow a | awk -F: 'NR==1 {printf "%d ", $1}; END{print $1}'
3 11

$ read first last <<< $(grep -n stackoverflow a | awk -F: 'NR==1 {printf "%d ", $1}; END{print $1}')

$ echo "first=$first, last=$last"
first=3, last=11

Answer 2

If you know an upper bound of how many lines there can be (say, a million), then you can use this simple abusive script:

(grep -A 100000 stackoverflow | grep -B 1000000 stackoverflow) < file

You can append | tail -n +2 | head -n -1 to strip the border lines as well:

(grep -A 100000 stackoverflow | grep -B 1000000 stackoverflow
  | tail -n +2 | head -n -1) < file