Sed command help to summarize similar log messages - sed

Question

I'm trying to craft a log file summarisation tool for an application that creates a lot of duplicate entries with only a different suffix to indicate point of execution.
Here's a genericized version:
A text_file (infile_grocery.txt) with these contents.
milk skim fruit apple banana
milk skim fruit orange
milk skim fruit mango
milk skim fruit pomegranate
milk 2 percent fruit cherry tomato
milk 2 percent fruit peach
milk whole fruit pineapple
milk skim fruit strawberry raspberry
milk skim fruit strawberry rhubarb
milk whole fruit pineapple
What I'm hoping to get is:
milk skim fruit apple banana, orange, mango, pomegranate
milk 2 percent fruit cherry tomato, peach
milk whole fruit pineapple
milk skim fruit strawberry raspberry, strawberry rhubarb
milk whole fruit pineapple
The command line I've currently cooked up is:
sed -rn "{H;x;s|^(.+) fruit ([^\n]+)\n(.*)\1 fruit (.+)$|\1 fruit \2, \4|;x}; ${x;s/^\n//;p}" infile_grocery.txt
But the results I'm getting are:
milk skim fruit apple banana, mango, strawberry raspberry
milk skim fruit strawberry rhubarb
milk whole fruit pineapple
I'm discarding input somehow. Any gurus with a better idea how to structure this?

Answer 1

This is a awk solution.
awk -F fruit '
$1==x{
printf ",%s", $2
next
}
{
x=$1
printf "\n%s", $0
}
END {
print ""
}' input.txt
Output
milk skim fruit apple banana, orange, mango, pomegranate
milk 2 percent fruit cherry tomato, peach
milk whole fruit pineapple
milk skim fruit strawberry raspberry, strawberry rhubarb
milk whole fruit pineapple

Answer 2

This might work for you (GNU sed):
sed ':a;$!N;s/^\(\(.*fruit\).*\)\n\2\(.*\)/\1,\3/;ta;P;D' file
Explanation:
:a is a place holder for a loop
$!N append a newline followed by the next line except on the last line.
s/^\(\(.*fruit\).*\)\n\2\(.*\)/\1,\3/ collect everything upto the newline into back reference 1 (aka \1). Within this collect everything from the beginning of the line upto and including the word fruit into back reference 2 (aka \2). Collect everything following the matching \2 into back reference 3 (aka \3). Replace this regexp with back reference 1, followed by a comma, a space and then back reference 3.
ta if the substitution was true loop to place holder :a
P if the substitution was false print upto and including the first newline in the pattern space.
D if the substitution was false delete upto and including the first newline in the pattern space.

Answer 3

opref=""
nline=""
while read line; do
pref=`echo $line | sed 's/\(.*fruit\).*/\1/'`
item=`echo $line | sed 's/.*fruit\s\(.*\)/\1/'`
if [ "$opref" == "$pref" ]; then
nline="$nline, $item"
else
[ "$nline" != "" ] && echo $nline
nline=$line
fi
opref=$pref
done < input_file