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bashshdash-shell

Strange dash arithmetics

Having the following:

#!/usr/bin/env dash
seq -w 10 | while read -r num
do
    echo $num: $((num + 1))
done

prints

01: 2
02: 3
03: 4
04: 5
05: 6
06: 7
07: 8
sd: 3: sd: Illegal number: 08

Can anyone explain what is the problem with above dash artihmetic?

note, it is an dash (not bash) script.

Tagged it as bash too, for more attention from bash-experts too. :)

Solution

  • Problem is leading 0 in your seq output that makes it an octal number and anything above 07 is an invalid octal number.

    Note that this script will work fine without error:

    seq 10 | while read -r num; do echo "$num: $((num + 1))"; done