On Thu, 21 Oct 2021 08:46:17 -0600 Glenn Golden <g...@zplane.com> wrote:
> -----------------------------------------------------------------------------
> NOTE
> For historical and back-compatibility reasons, certain bare option-like
> strings cannot be emitted without setting POSIXLY_CORRECT, and the bare
> string '-n' cannot be emitted at all. Prefixing or suffixing such strings
> with quoted whitespace (e.g. ' -n') can be used as a workaround for this
> peculiarity. More generally, printf(1) is recommended as a more modern
> and flexible replacement for tasks historically performed by echo(1).
> -----------------------------------------------------------------------------
>
> Something like this seems to get the job done: Briefly states the issue,
> why it exists, provides a workaround, and cheerleads for modernization.
This note does seem to be in order and it will certainly benefit everyone
who may read the manpage. It is not entirely accurate, however. `echo`,
when run with the `-e` option, does allow backslash escapes for arbitrary
octal and hexadecimal representations of character codes. Hence both of
the following commands will produce the string `-n` as output:
echo -e '\0055n'
echo -e '\x2dn'
For the sake of correctness, one might want to reword the note somewhat
like this:
For historical and back-compatibility reasons, certain bare option-like
strings cannot be passed to echo as non-option arguments. The only way
to echo the string '-n', for instance, is to specify the dash in either
octal or hexadecimal representation (e.g. 'echo -e "\x2dn"'). It is
therefore not advisable to use echo(1) for printing unknown or variable
arguments. More generally, printf(1) is recommended as a more modern
and flexible replacement for tasks historically performed by echo(1).
Regards
Frank
