Text Processing - How to get pattern A matching line until first occurrence of pattern B matching line?

Question

I want to get the lines that, in reverse order, match from pattern A matching line to the first occurrence of pattern B matching line along with the lines that it passes.

UPDATED: example_file.txt

ISA*00*          *00*          *ZZ*SIX-SIX6      *12*666666666666     *66666666*6666*U*666666666*6666666666*0*P*\
GS*FA*SIX-SIX-SIX*666666666*6666666*6666*6666*X*66666
ST*666*666
AK1*SX*666
AK2*777*6666666
AK5*A
AK2*777*7777777
AK3*S6*5**3
AK3*A2*5**3
AK4*3*6969*4
AK4*7*6969*4
AK5*R*5
AK2*777*6666666
AK5*A
AK2*777*69696969
AK3*J7*5**3
AK4*3*6969*4
AK5*R*5
AK9*P*20*20*19
SE*69*6969
GE*1*6767
IEA*1*0000000000

What I want is to get, from the bottom up, all the AK5 pattern with R after it, like this:

Pattern A: AK5*R

and get all the lines going up until the first occurrence of pattern B is matched. e.g.:

Pattern B: AK2

Desired output:

First Pattern A matched will be called E1

AK2*777*7777777
AK3*S6*5**3
AK3*A2*5**3
AK4*3*6969*4
AK4*7*6969*4
AK5*R*5

UPDATED: Second Pattern A matched will be called E2

AK2*777*69696969
AK3*J7*5**3
AK4*3*6969*4
AK5*R*5

and so on if there are more than 1 pattern A matched.

EDIT: I know sed can do this but I still don't have any luck in getting the line from each pattern A matched to its first occurrence of pattern B matched and store them in a temporary text file to be process further.

This is my example sed command that gets all available pattern B in the example_file.txt

sed -ne '/AK2\*/,/\AK5\*R/p' example_file.txt

Example command logical scenario:

A="AK5\*R"
B="AK2"

find the first $A < example_file.txt; # AK5\*R
move to previous line until first occurrence of $B line; # AK2*any_number*any_number
get all lines from first $A to its first occurrence of $B and store in a text file; # result > e1.txt
# The same way goes to the second occurrence of pattern A.

(NOTE: First occurrence of $B meaning, starting from each $A line get $A line and the previous lines until the very first $B matching line it encounters. So e.g. if the first $A line starts from the middle line of a file like in line number 50 if the file has 100 total lines then from there move to the previous line until command encounters the very first $B line it sees.) See example below.

example_file2.txt

ISA*00*          *00*          *ZZ*SIX-SIX6      *12*666666666666     *66666666*6666*U*666666666*6666666666*0*P*\
GS*FA*SIX-SIX-SIX*666666666*6666666*6666*6666*X*66666
ST*666*666
AK1*SX*666
AK2*777*6666666
AK5*A
AK2*777*7777777
AK5*A
AK2*777*888888
AK5*A
AK2*777*7777777
AK5*A
AK2*777*5555555
AK5*A
AK2*777*7777777
AK5*A
AK2*777*4545435
AK5*A
AK2*777*7777777
AK5*A
AK2*777*7777777
AK3*S6*5**3
AK3*A2*5**3
AK4*3*6969*4
AK4*7*6969*4
AK5*A
AK2*777*0987654
AK3*S6*5**3
AK3*A2*5**3
AK4*3*6969*4
AK4*7*6969*4
AK5*R*5
AK2*777*7777777
AK3*S6*5**3
AK3*A2*5**3
AK4*3*6969*4
AK4*7*6969*4
AK5*A
AK2*777*7777777
AK3*S6*5**3
AK3*A2*5**3
AK4*3*6969*4
AK4*7*6969*4
AK5*A

Output:

AK2*777*0987654
AK3*S6*5**3
AK3*A2*5**3
AK4*3*6969*4
AK4*7*6969*4
AK5*R*5

Answer 1

Reading again your description I understand that you want the first match of pattern B from the bottom up until (going up) the first match of pattern A. But the resulting sections should be in the order that the file has.

That requires a lot of logic. The following shell script does it all. Will place the results in the correct internal order in files E and some number, first file (E1) will have the first match from the top, last file will have the last match section.

#!/bin/bash

rm -rf resE* E*

tac ../example_file.txt |
    awk 'BEGIN{i=1}
         /^AK5\*R.*/{p=1}
         {if(p==1){f="resE" i;print($0)>>f;close(f)}}
         /^AK2.*/{if(p==1){i++};p=0}
        '
set -- resE* 
c=$#
for (( i=1;i<=$c;i++)); do
    pos=$(($c-$i+1))
    [ -f "$1" ] && tac "$1" > "E$pos"
    shift
done

The resulting ranges will be:

$ cat E1
AK2*777*7777777
AK3*S6*5**3
AK3*A2*5**3
AK4*3*6969*4
AK4*7*6969*4
AK5*R*5

$ cat E2
AK2*777*7777777
AK3*J7*5**3
AK4*3*6969*4
AK5*R*5

Answer 2

POSIX ex to the rescue again!

ex is the POSIX-specified scriptable file editor. For anything involving backwards addressing, it's usually a far better solution than Awk or Sed.

The following one-liner works perfectly on your example_file2.txt:

printf '%s\n' 'g/AK5[*]R/?AK2?,.p' | ex example_file.txt

On your example_file.txt, it also works, but because the global command in ex can't write to a separate destination for each range acted upon, the desired two output files are merged like so:

AK2*777*7777777
AK3*S6*5**3
AK3*A2*5**3
AK4*3*6969*4
AK4*7*6969*4
AK5*R*5
AK2*777*69696969
AK3*J7*5**3
AK4*3*6969*4
AK5*R*5

However, this is easy enough to handle—with another POSIX tool, csplit, which is designed to split files according to a "context."

Portable POSIX solution:

patA='AK5[*]R'
patB='AK2'

printf '%s\n' "g/$patA/?$patB?,.p" |
  ex example_file.txt |
  csplit -f my_unique_prefix_ -n 1 -s -k - "/$patB/" '{999}'

for f in my_unique_prefix_*; do
  mv "$f" "e${f##my_unique_prefix_}.txt";
done

rm e0.txt

There is one final element to make this a perfect solution, which is to renumber the files in reverse order. I haven't done this portion.

---

If you don't care about the file numbering being in the same order as the file, and if you don't mind if the extension .txt is omitted, and if you don't mind if the files are numbered from e01 rather than from e1, and if you don't mind a diagnostic message being printed about how many lines were put in each file, then we can simplify:

patA='AK5[*]R'
patB='AK2'

printf '%s\n' "g/$patA/?$patB?,.p" |
  ex example_file.txt |
  csplit -f e -k - "/$patB/" '{999}'

rm e00