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 shall 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 forbids a conforming application from using any options (even if the implementation provides them) while ISO POSIX (2003) specifies behavior if the first operand is the string -n.