echo - produce message in a shell script
echo [ -n | -e ] args...
Echo prints its arguments on the standard output, separated by spaces.
Unless the -n option is present, a newline is output following the
arguments. The -e option causes echo to treat the escape sequences
specially, as described in the following paragraph. Only one of the
options -n and -e may be given.
If any of the following sequences of characters is encountered during
output, the sequence is not output. Instead, the specified action is
\b A backspace character is output.
\c Subsequent output is suppressed. This is normally used at the end
of the last argument to suppress the trailing newline that echo
would otherwise output.
\f Output a form feed.
\n Output a newline character.
\r Output a carriage return.
\t Output a (horizontal) tab character.
\v Output a vertical tab.
Output the character whose value is given by zero to three digits.
If there are zero digits, a nul character is output.
\\ Output a backslash.
Remember that backslash is special to the shell and needs to be escaped.
To output a message to standard error, say
echo message >&2
The octal character escape mechanism (\0digits) differs from the C