Print lines of a file between two matching patterns [duplicate]

Question

How can I print all the lines between two lines starting with one pattern for the first line and ending with another pattern for the last line?

---

Update
I guess it was a mistake to mention that this document is HTML. I seem to have touched a nerve, so forget that. I'm not trying to parse HTML or do anything with it other than print a section of a text document.

---

Consider this example:

aaa
bbb
pattern1
aaa pattern2
bbb
ccc
pattern2
ddd
eee
pattern1
fff
ggg

Now, I want to print everything between the first instance of pattern1 starting at the beginning of a line and pattern2 starting at the beginning of another line. I want to include the pattern1 and pattern2 lines in my output, but I don't want anything after the pattern2 line.

pattern2 is found in one of the lines of the section. I don't want to stop there, but that's easily remedied by indicating the start of the line with ^.

pattern1 appears on another line after pattern2, but I don't want to look at that at all. I'm just looking for everything between the first instance of pattern1 and the first instance of pattern2, inclusive.

I found something that almost gets me there using sed:

sed -n '/^pattern1/,/^pattern2/p' inputfile.txt

... but that starts printing again at the next instance of pattern1

I can think of a method using grep -n ... | cut -f1 -d: twice to get the two line numbers then tail and head to get the section I want, but I'm hoping for a cleaner way. Maybe awk is a better tool for this task?

When I get this working, I hope to tie this into a git hook. I don't know how to do that yet, either, but I'm still reading and searching :)

Thank you.

Answer 1

You can make sed quit at a pattern with sed '/pattern/q', so you just need your matches and then quit at the second pattern match:

sed -n '/^pattern1/,/^pattern2/{p;/^pattern2/q}'

That way only the first block will be shown. The use of a subcommand ensures that ^pattern2 can cause sed to quit only after a match for ^pattern1. The two ^pattern2 matches can be combined:

sed -n '/^pattern1/,${p;/^pattern2/q}'

Answer 2

As a general approach, with sed, it's easy to print lines from one match to another inclusively:

$ seq 1 100 > test
$ sed -n '/^12$/,/^15$/p' test
12
13
14
15

With awk, you can do the same thing like this:

$ awk '/^12$/{flag=1}/^15$/{print;flag=0}flag' test
12
13
14
15

You can make these non-inclusive like this:

$ awk '/^12$/{flag=1;next}/^15$/{flag=0}flag' test
13
14

$ sed -n '/^12$/,/^15$/p' test | sed '1d;$d'
13
14