The echo command is as specified in ISO POSIX (2003), but with the following differences.
Implementations may support implementation-defined options to echo. The behavior of echo if any arguments contain backslashes is also implementation defined.
Conforming applications should not run echo with a first argument starting with a hyphen, or with any arguments containing backslashes; they should use printf in those cases.
Note: The behavior specified here is similar to that specified by ISO POSIX (2003) without the XSI option. However, the LSB strongly recommends conforming applications not use any options (even if the implementation provides them) while ISO POSIX (2003) specifies behavior if the first operand is the string -n.