string to standard output; if -n is
specified, the output is not terminated by a newline.
string is supplied, echo a newline.
In the Korn shell, echo is just an alias for print -.
(See also echo in Section 2.)
echo understands special escape characters,
which must be quoted (or escaped with a \)
to prevent interpretation by the shell:
Suppress the terminating newline (same as -n).
ASCII character represented by octal number
is 1, 2, or 3 digits and is preceded by a 0.
echo "testing printer" | lp$
echo "Warning: ringing bell \007"