Linux command or script counting duplicated lines

Question

If I have a text file with the following conent

red apple
green apple
green apple
orange
orange
orange

Is there a Linux command or script that I can use to get the following result?

1 red apple
2 green apple
3 orange

Answer 1

Can you live with an alphabetical, ordered list:

echo "red apple
> green apple
> green apple
> orange
> orange
> orange
> " | sort -u 

?

green apple
orange
red apple

or

sort -u FILE

-u stands for unique, and uniqueness is only reached via sorting.

A solution which preserves the order:

echo "red apple
green apple
green apple
orange
orange
orange
" | { old=""; while read line ; do   if [[ $line != $old ]]; then  echo $line;   old=$line; fi ; done }
red apple
green apple
orange

and, with a file

cat file | { 
old=""
while read line
do
  if [[ $line != $old ]]
  then
    echo $line
    old=$line
  fi
done }

The last two only remove duplicates, which follow immediately - which fits to your example.

echo "red apple
green apple
lila banana
green apple
" ...

Will print two apples, split by a banana.