[throw0101b]

     The newline may also be suppressed by appending `\c' to the end of the
     string, as is done by iBCS2 compatible systems.  Note that the -n option
     as well as the effect of `\c' are implementation-defined in IEEE Std
     1003.1-2001 ("POSIX.1") as amended by Cor. 1-2002.  For portability, echo
     should only be used if the first argument does not start with a hyphen
     (`-') and does not contain any backslashes (`\'). If this is not suffi-
     cient, printf(1) should be used.

* https://man.freebsd.org/cgi/man.cgi?query=echo

     \c      Suppress the <newline> that otherwise follows
             the final argument in the output. All
             characters following the '\c' in the arguments
             shall be ignored.

* https://man7.org/linux/man-pages/man1/echo.1p.html