[Discuss] "M-" notation

[Richard Pieri]

On 7/6/2012 6:56 AM, Daniel Feenberg wrote:
> Actually, tab and NL are not translated. From the man page:
>
>     -v, --show-nonprinting
>                use ^ and M- notation, except for LFD and TAB

That's output from cat.  If you were to run the file through 'tr -d 
[:cntrl:]' then LFD and TAB characters would be removed.  That's the 
mess.  Go ahead and try it if you don't believe me.

> I just tested it, the man page is almost right in that CR is also not
> translated. Anyway, I don't want to delete all the "M-" characters, just
> "M- " (em minus space). That character acts like a tab on my terminal,
> but seems to be a tab with the high bit set.

There are no "em minus space" characters.  They don't exist.  That is 
cat's human-readable translation of nonprinting characters.  If you want 
to remove these nonprinting characters then you have to do it by 
interpreted sequences (like "\a") or octal codes.

-- 
Rich P.