'tr' character class support?

Jordan Geoghegan jordan at geoghegan.ca
Fri Jul 10 17:26:43 EDT 2020

On 2020-07-10 14:15, Magnus Kroken wrote:
> Hi Jordan
> On 10.07.2020 22:45, Jordan Geoghegan wrote:
>> Hey folks,
>> Does the 'tr' utility support character classes in OpenWRT? I was 
>> playing around with an OpenWRT x86_64 VM and I noticed that 'tr' 
>> doesn't seem to support character classes.
>> The command " echo HELLO | tr '[:upper:]' '[:lower:]' "  does not 
>> convert to the text to lowercase as it should (and as required by 
>> POSIX).
> This would be expected behavior. OpenWrt disables tr character classes 
> in BusyBox by default, see [1]:
>         bool
>         default n
>         bool
>         default n
> I don't know what the size cost in the BusyBox binary is, but that 
> will likely be the deciding factor for such a change.
> 1: 
> https://git.openwrt.org/?p=openwrt/openwrt.git;a=blob;f=package/utils/busybox/Config-defaults.in
> Regards,
> Magnus Kroken

Hi Magnus,

Thanks for confirming that so quickly.

I obviously understand that space saving is essential to OpenWRT, but 
POSIX does require[1] that 'tr' support character classes:

	      Represents all characters belonging to the defined character class, as defined by the current setting of the LC_CTYPE  locale  cate-
	      gory. The following character class names shall be accepted when specified in string1:

		alnum	 blank	 digit	 lower	 punct	 upper
		alpha	 cntrl	 graph	 print	 space	 xdigit

1: https://www.unix.com/man-page/posix/1posix/tr/


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