(1) Given a string, I replace spaces with $'\n' using sed:
echo "one two" | sed 's/ /$'"'"'\\n'"'"'/g'
This outputs:
# one$'\n'two
(2) Note that echoing this output of (1):
echo one$'\n'two
results in:
# one
# two
(3) I echo the output of (1) in another way, by piping the output of (1) into xargs echo:
echo "one two" | sed 's/ /$'"'"'\\n'"'"'/g' | xargs echo
But I don't get the same output as (2):
# one$\ntwo
What does xargs do when formatting the input of a string containing $'\n'?
Why is echoing a string with $'\n' not the same as using xargs echo on the same string?
When you write
echo one$'\n'two
at the command line, bash replaces the "$'\n'" with a newline. But when you pass it to xargs no such replacement can happen.
But piping it to xargs will still not do what you want, since by default xargs uses the newline as an argument separator:
$ echo "one two" | tr ' ' '\n' | xargs echo
one two
You must tell xargs to use a different separator, even if it is a bogus one:
$ echo "one two" | tr ' ' '\n' | xargs -0 echo
one
two