Super Speedy Hexadecimal or Octal Calculations and Conversions to Decimal.

echo "$(( 0x10 )) - $(( 010 )) = $(( 0x10 - 010 ))"
^Hexadecimal Ten minus Octal Ten is Eight(in Decimal). echo "$(( 0xaf )) = $(( 0257 ))" ^Hexadecimal AF and Octal 257 are both Decimal 175.
Sample Output
16 - 8 = 8

175 = 175

By: asmoore82
2009-06-08 19:35:53

What Others Think

The basic point here is that (I'm assuming bash) the shell understands hexadecimal and octal numbers, when strings of digits (0-9,a-f) are preceded by 0x or 0.
bwoodacre · 688 weeks and 1 day ago
That's excellent, which I knew about it sooner!
nanreh · 688 weeks and 1 day ago
Yes, the general idea is that BASH's $(( ... )) construct accepts hex with "0x" and *ASSUMES* numbers with leading zeros are octal. This assumption can cause weird bugs when scripting; especially when time and dates are involved. This produces an error only in the months of August and September: currentmonth=$( date +%m ) echo "There are $(( 12 - currentmonth )) months left in the year."
asmoore82 · 688 weeks ago
After some googling, it seems you can force a particular base on an expression via prefixing "base#" to a number. In august/september 'date +%m' will yield 08 and 09, so to fix this the echo would read: echo "There are $(( 12 - 10#currentmonth )) months left in the year." to force current month to be interpreted in base 10. Obviously the base must be specified in base 10, although it would be an interesting way to screw up somebody's bash session (if it were possible) to change the default number base. :-)
bwoodacre · 686 weeks and 1 day ago

What do you think?

Any thoughts on this command? Does it work on your machine? Can you do the same thing with only 14 characters?

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