Re: Trying to replace a bashism in bourne sh

On 06/11/2023 18:45, D'Arcy Cain wrote:
> I need to do this;
> 
>   ifconfig_eth3="inet $((16#c0a8c0${me} + 100))/24"
> 
> Problem is that I need to do this at boot time but then it runs as
> bourne sh.  Does anyone have an equivalent for sh?

I'm not totally familiar with bash but that (16#c0a8c0) is a hexadecimal
number equivalent to an address triplet 192.168.192. I'd guess ${me} is
also a 2 digit hex value and for some reason 100 is added. The whole
thing is assembling an IPv4 CIDR network address (the /24 is the netmask
bit). Try something along the lines of

ifconfig_eth3="192.168.192."$((me_in_decimal+100))"/24"

if you can arrange for ${me} to be specified in decimal rather than hex.
If you can't then something like

ifconfig_eth3="192.168.192."$(hex_to_decimal_plus_100 ${me})"/24"

where implementing the function hex_to_decimal_plus_100 is left as an
exercise for the reader. :-)

-- 
We build our computer systems the way we build our cities; over time,
without a plan, on top of ruins.
			— Ellen Ullman