Jonathan Tan <jonathantanmy@xxxxxxxxxx> writes:
>> + - In 'printf' format string, do not use hexadecimals, as they are not
>> + portable. Write
>> +
>> + CENT=$(printf "\302\242")
>> +
>> + not
>> +
>> + CENT=$(printf "\xc2\xa2")
>
> I've checked with "dash" and this applies to any quoted string, not just
> when passed to printf. I'll prepare a patch describing this.
What do you mean by "any quoted string"?
I think built-in 'echo' of dash takes "\302\242" and emits the
cent-sign (but /bin/echo may not), but I do not think it is "any
quoted string". To wit:
dash$ echo '\302\242'
¢
The echo built into dash shows the cent-sign. The example does not
let us tell if is the shell (i.e. the 'echo' command sees the
cent-sign in its argv[1]) or if it is the command (i.e. the 'echo'
sees 8-byte string "bs three zero two bs two four two" in its
argv[1], and shows that as the cent-sign), though.
dash$ /bin/echo '\302\242'
\302\242
This shows that shell is not doing anything fancy. /bin/echo gets
the 8-byte string in its argv[1] and emits that as-is.
dash$ /bin/echo "\302\242"
\302\242
Again this shows the same; I added this example to demonstrate that
it is _not_ like the shell interprets the backslashed octal strings
depending on how they are quoted.
dash$ printf "%s\n" '\302\242'
\302\242
dash$ printf "%s\n" "\302\242"
\302\242
And these demonstrates that argv[2] given to printf in these cases
are 8-byte string "bs three zero two bs two four two" and the shell
is not doing anything fancy.
So, I would suggest not saying "any quoted string". In addition,
even though dash's built-in echo that recognizes "\0num" seems to be
conformant to what POSIX specifies (cf. [*1*]), GNU requires "-e" in
order to do so in both standalone 'echo' binary and one built into
'bash', so we cannot rely on this POSIX behaviour when writing a
portable script. Hence, I would recommend us to focus on giving a
piece of advice on use of printf in this part of the documentation.
[References]
*1* https://pubs.opengroup.org/onlinepubs/9699919799/utilities/echo.html
*2* https://www.gnu.org/software/coreutils/manual/html_node/echo-invocation.html
