Regex expression matching block of lines - regex

Question

I have this kind of file:
Analysis of its root cause:
Blablablablabla
blabablabkjhjk
kjbsqbdqbds
Details of the fix
blablabla
Analysis of its root cause:
fddsfsdfsdfdsfs
blnskdbbqbbb
xxxxggggggg
Details of the fix
blablabla
Analysis of its root cause is repeated x times in the file. I would like to get the block of text delimited by "Analysis of its root cause" and "Details of the fix".
Thanks a lot for your help.

Answer 1

I'm pretty sure there is some better way to do this, but that's what I could manage:
/(?(?<=Analysis of its root cause:\n)((.*\n)*)(?=Details of the fix\n))/gU
I'm using positive lookahead and lookbehind, and the following modifiers:
g - global - Don't return after first match
u - Ungreedy - Make quantifiers lazy
Try it online: https://regex101.com/r/xpz7pg/2

Answer 2

Not a regex answer, but using perl
Put your lines into a single file.
perl -e '$/="Analysis of its root cause:"; #Sets the record delimiter
while(<>){ #Iterates over the file, record by record
chomp; #Removes the delimiter
if ($_ =~ /\n(.*?)\nDetails of the fix\n(.*)\n/s){ #Matches strings between Details of the fix. . is allowed to match newline
print "ONE:$1TWO:$2"} # $1 is the analysis, $2 is the details
}'
file.txt
Output
ONE:Blablablablabla
blabablabkjhjk
kjbsqbdqbds
TWO:blablabla
ONE:fddsfsdfsdfdsfs
blnskdbbqbbb
xxxxggggggg
TWO:blablabla