Why 08, 09 cannot be used as 8 ,9?

[arthurzzk]

If you do $((08+1)) or $((09+1)) in terminal, linux shows an error.
However, you can use 07,06,05,04,03, 02,01,00, and Linux treat them as 7,6,5,4,3,2,1,0 .

Can someone tell me how to make 08 and 09 work in this way?

[Motoma]

If you do $((08+1)) or $((09+1)) in terminal, linux shows an error.
However, you can use 07,06,05,04,03, 02,01,00, and Linux treat them as 7,6,5,4,3,2,1,0 .

Can someone tell me how to make 08 and 09 work in this way?

That's easy!
Prefacing a number with a 0 when it isn't the only digit before a decimal (.) will cause most programming languages to treat is as Octal (base 8). The highest numeric digit in octal is 7, thus 8 and 9 will not show up.

If you don't believe me, try 077 and see what you get.

[arthurzzk]

can someone tell me how to make 08 and 09 work as 8, 9?

[Motoma]

can someone tell me how to make 08 and 09 work as 8, 9?

As far as I know, this cannot be done in the way you've posed the question. This is similar to asking for 0x11 be represented as 11 (which is certainly not the case).

[ValHolla]

if you need them to be viewed as 08 and 09 you can do your calculations with the decimal equivalents 0 - 9 and use printf to display them with the leading 0 (zero)

[michaelb]

This behavior seems to vary depending on the shell:

~> echo $SHELL
/usr/local/bin/bash
~> echo $((09+7))
-bash: 09: value too great for base (error token is "09")
~> ksh
$  echo $((09+7))
16
$

There's also the typeset built-in which can be used for formatting:

$ 
$ typeset -Z2 num1=9  
$ typeset -Z3 num2   
$ num2=8
$ echo $num1
09
$ echo $num2
008
$ echo $((num1 * num2))
72
$

[shamrockjade]

This worked for me in the bash shell. If I tried to default the dirNUM to 3 digits first then I would error out with the 08 errors.

      dirNUM=1
      until [[ $dirNUM == 367 ]]
      do
         # Change directory number to 3 digits
         if [[ ! -d ${root_dir}/$(printf "%.3d" $dirNUM) ]]
         then
            mkdir ${root_dir}/$(printf "%.3d" $dirNUM)
         fi
         ((dirNUM+=1))
      done