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Tim
Asked: 2015-05-10 05:17:23 +0800 CST

Why does bash thinks that 010 is 8?

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Why does bash think the number 010 = 8?

x=010
echo $x
  010
echo $(( x+0 ))
  8
echo $(( x-2 ))
  6

I thought it might be binary, but 010 = 10 = 2. So why does it get 8, and how can I make it think 010 = 10 (and 010 - 2 = 8)?

bash

1 Answers

  1. Best Answer

    Number sequences starting with a 0 are interpreted as octal numbers.
    Octal 10 = decimal 8.

    To get bash to treat it as a decimal number, remove the leading zero or force decimal with:

    N=010
N=$((10#$N))

    Generally that works for all bases, just replace the 10 with the base that you want:

    N=[base#]n
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