Integer conversions in bash

Since version 2, bash support a single aritmethic operations. Altough bash is not a mathematical shell (use bc instead), you can perform certain conversions using the bash arithmetic logic.

For example you can remove the left zeroes in a decimal number without require any external utility or print formats, let’s suppose that you want to strip zeroes from the number 007, which is stored in bond variable.

$ echo $bond
$ let nozeros=10#$bond
$ echo $nozeros

In many forums and mailing list, people need to use ugly sed expressions, or awk invokation, but (with bash) it’s just simply 🙂

Using the same trick, you can perform a base conversions, for example:

$ let i=0x10
$ echo $i
$ let i=2#10000
$ echo $i

Or create an easy number checking:

$ is_decimal () { let i=10#$1 2>/dev/null; }
$ is_decimal 'a' || echo Nop
$ is_decimal 56 && echo 'Yep'


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