Let's start with this:
echo "1 2 3 4 5 6" | perl -pe 's/ /\n/g' > unix.txt
echo "1 2 3 4 5 6" | perl -pe 's/ /\r\n/g' > dos.txt
echo "1 2 3 4 5 6" | perl -pe 's/ /\r/g' > mac.txt
When I open the dos file with vim I get the annoying ^M and vim doesn't recognize the dos file as a dos format even with set ffs=unix,dos,mac.
Thus I investigated a bit further:
$ hexdump -C unix.txt
00000000 31 0a 32 0a 33 0a 34 0a 35 0a 36 0a |1.2.3.4.5.6.|
$ hexdump -C dos.txt
00000000 31 0d 0a 32 0d 0a 33 0d 0a 34 0d 0a 35 0d 0a 36 |1..2..3..4..5..6|
00000010 0a |.|
$ hexdump -C mac.txt
00000000 31 0d 32 0d 33 0d 34 0d 35 0d 36 0a |1.2.3.4.5.6.|
I notice that a 0a appears at the end of each file. I don't understand why. How to get rid of it?
echo "1 2 3 4 5 6" | hexdump -C
00000000 31 20 32 20 33 20 34 20 35 20 36 0a |1 2 3 4 5 6.|
--------------------------------------------^^
echo -n "1 2 3 4 5 6" | hexdump -C
00000000 31 20 32 20 33 20 34 20 35 20 36 |1 2 3 4 5 6|
From man echo
-n do not output the trailing newline