# cat copies its input to stdout
<
foo
$ cat
>
foo

# or, given a bad flag, prints a platform-specific error and exits with non-zero status
$ cat --no-such-flag
>2 /(unrecognized|illegal) option/
>= !0

# echo ignores the input and prints a newline.
# We use an explicit >2 (or >=) to delimit the whitespace which
# would otherwise be ignored.
$ echo
>

>2