Comment by capitainenemo
2 months ago
In most linux terminals, what you pass it is just a sequence of bytes that is passed unmangled. And since this technique is UTF-8 compliant and doesn't use any extra glyphs, it is invisible to humans in unicode compliant terminals. I tried it on a few. It shows up if you echo the sentence to, say, xxd ofc.
(unlike the PUA suggestion in the currently top voted comment which shows up immediately ofc)
Additional test corrections: While xxd shows the message passing through completely unmangled on pasting it into the terminal, when I selected from the terminal (echoed sentence, verified unmangled in xxd, then selected and pasted the result of echo), it was truncated to a few words using X select in mate terminal and konsole - I'm not sure where that truncation happens, whether it's the terminal or X. In xterm, the final e was mangled, and the selection was even more truncated.
The sentence is written unmangled to files though, so I think it's more about copying out of the terminal dropping some data. Verified by echoing the sentence to a test file, opening it in a browser, and copying the text from there.
On MacOS, kitty shows an empty box, then an a for the "h󠅘󠅕󠅜󠅜󠅟󠄐󠅖󠅕󠅜󠅜󠅟󠅧󠄐󠅘󠅑󠅓󠅛󠅕󠅢󠄐󠄪󠄙a" post below. I think this is fair and even appreciated. Mac Terminal shows "ha". That "h󠅘󠅕󠅜󠅜󠅟󠄐󠅖󠅕󠅜󠅜󠅟󠅧󠄐󠅘󠅑󠅓󠅛󠅕󠅢󠄐󠄪󠄙a" (and this one!) can be copied and pasted into the decoder successfully.