[GTALUG] tr: Illegal byte sequence

[Bill Thanis]

The Locale indirectly controls the character encoding on the shell. that is
the reason why the locale settings have to do with this. I may be wrong,
but I believe the shell on the MAC is hardcoded with a specific character
encoding, probably 7 bit ascii. Try changing your count to 128.

Bill


On Wed, Sep 26, 2018 at 10:41 AM Giles Orr via talk <talk at gtalug.org> wrote:

> I wrote a random password generator shell script, the core of which is
> this one-liner:
>
> dd if=/dev/urandom bs=1 count=256 2>/dev/null | tr -dc
> 'A-Za-z0-9!@$%^&*(){}[]=+-_/?\|~`' | head -c 32
>
> The very ugly string 'A-Za-z0-9!@$%^&*(){}[]=+-_/?\|~`' is the ALLOWED
> values.  The two counts are replaced by variables, the first 'count='
> needing to be a lot bigger than the final '-c <number>' which is the length
> of the password generated.  The size difference is necessary because 'tr'
> throws away a lot of values.
>
> I've never had a problem with this on Linux, but on a Mac under some
> circumstances we get:
>
>     tr: Illegal byte sequence
>
> My coworker, who's also using the script, always got that error.  It seems
> to come down to locale settings.  Mine by default are:
>
> $ locale
> LANG="en_CA.UTF-8"
> LC_COLLATE="en_CA.UTF-8"
> LC_CTYPE="en_CA.UTF-8"
> LC_MESSAGES="en_CA.UTF-8"
> LC_MONETARY="en_CA.UTF-8"
> LC_NUMERIC="en_CA.UTF-8"
> LC_TIME="en_CA.UTF-8"
> LC_ALL=
>
> My co-worker's settings are:
>
> LANG="en_US.UTF-8"
> LC_COLLATE="en_US.UTF-8"
> LC_CTYPE="en_US.UTF-8"
> LC_MESSAGES="en_US.UTF-8"
> LC_MONETARY="en_US.UTF-8"
> LC_NUMERIC="en_US.UTF-8"
> LC_TIME="en_US.UTF-8"
> LC_ALL="en_US.UTF-8"
>
> A reliable fix (so far ...):
>
>     $ export LC_CTYPE=C
>     $ export LC_ALL=C
>     $ dd if=/dev/urandom bs=1 count=256 2>/dev/null | tr -dc
> 'A-Za-z0-9!@$%^&*(){}[]=+-_/?\|~`' | head -c 32
>     z%V;d9uZfWLTgsT*J]Bz`mAmA
>
> I'd really like to understand what the problem is, why 'tr' barfs, and
> what the 'locale' settings have to do with this.  Thanks.
>
> (Should anyone have arguments against this as a method of password
> generation, I'll entertain those too.  And yes, I'm aware of 'apg' but it's
> not readily available for Mac and this is much lighter weight.)
>
> --
> Giles
> https://www.gilesorr.com/
> gilesorr at gmail.com
> ---
> Talk Mailing List
> talk at gtalug.org
> https://gtalug.org/mailman/listinfo/talk
>
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