How to print lines between pattern1 and 2nd match of pattern2

awksedtext processing

Test file is given below:

PATTERN1
a
b
c
PATTERN2
d
e
f
PATTERN2
g
h

I want to print line between PATTERN1 and 2nd match of PATTERN2:

PATTERN1
a
b
c
PATTERN2
d
e
f
PATTERN2

Best Answer

Here's one way to do it with sed:

sed '/PATTERN1/,$!d;/PATTERN2/{x;//{x;q;};g;}' infile

This just deletes all lines (if any) up to the first occurrence of PATTERN1 and then, on each line that matches PATTERN2 it exchanges buffers. If the new pattern space also matches, it means it's the 2nd occurrence so it exchanges back and quits (after auto-printing). If it doesn't match it means it's the 1st occurrence so it copies the hold space content over the pattern space via g (so now there's a line matching PATTERN2 in the hold buffer) and goes on...
and another way with awk:

awk '/PATTERN1/{t=1}; t==1{print; if (/PATTERN2/){c++}}; c==2{exit}' infile

It starts printing and counting lines matching PATTERN2 only when encountering a line matching PATTERN1 and exits when counter reaches 2.

Related Solutions

Delete a line containing “pattern1” first occurrence after “pattern2” last occurrence

This is an ex one-liner. (ex is the predecessor and scripted form of vi.)

printf '%s\n' '$?pattern2?/pattern1/d' x | ex file.txt

The x saves and exits. Change it to %p if you want to just print the altered file but not save changes (good for testing).

$ means last line of file; ?pattern2? is an address meaning the first result of a backwards search for pattern2 starting from the current position; /pattern1/ is a forward-searching address, and d is the line deletion command.

Use ex when you need forward AND backward addressing.

You can do the same thing interactively in vi or Vim:

vim file.txt

Then, type

:$?pattern2?/pattern1/d

and press Enter.

Then save and exit with :x Enter.

Removing text from pattern1 up to and including 2nd match of pattern2

This is quite the opposite of

How to print lines between pattern1 and 2nd match of pattern2?

With sed you'd do something like:

sed -n '/PATTERN1/,$!{         # if not in this range
p;d                            # print and delete
}
/PATTERN2/!d                   # delete if it doesn't match PATTERN2
x;//!d                         # exchange and then, again, delete if no match
: do                           # label "do" (executed only after the 2nd match)
n;p                            # get the next line and print
b do' infile                   # go to label "do"

or, in one line (on gnu setups):

sed -n '/PATTERN1/,$!{p;d;};/PATTERN2/!d;x;//!d;: do;n;p;b do' infile

Sure, it's easier with awk and counters. I'll leave that as an exercise for you...

Best Answer

Related Solutions

Delete a line containing “pattern1” first occurrence after “pattern2” last occurrence

Removing text from pattern1 up to and including 2nd match of pattern2

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