echo - write arguments to standard output
echo args ...
The echo(1) utility prints its arguments on the standard output, separated by spaces. The echo(1) utility treats escape sequences specially, as described in the following paragraph.
If any of the following sequences of characters is encountered during output, the sequence is not output. Instead, the specified action is performed:
The echo(1) utility is implemented as a shell regular built-in command.
The backslash character (\) is standard to the shell and must be escaped:
$ echo Here is a double backslash: \\\\
To output a message to standard error, enter
$ echo message >&2