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

10
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 · 642 weeks ago
That's excellent, which I knew about it sooner!
nanreh · 642 weeks 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 · 642 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 · 640 weeks 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?

You must be signed in to comment.

What's this?

commandlinefu.com is the place to record those command-line gems that you return to again and again. That way others can gain from your CLI wisdom and you from theirs too. All commands can be commented on, discussed and voted up or down.

Share Your Commands



Stay in the loop…

Follow the Tweets.

Every new command is wrapped in a tweet and posted to Twitter. Following the stream is a great way of staying abreast of the latest commands. For the more discerning, there are Twitter accounts for commands that get a minimum of 3 and 10 votes - that way only the great commands get tweeted.

» http://twitter.com/commandlinefu
» http://twitter.com/commandlinefu3
» http://twitter.com/commandlinefu10

Subscribe to the feeds.

Use your favourite RSS aggregator to stay in touch with the latest commands. There are feeds mirroring the 3 Twitter streams as well as for virtually every other subset (users, tags, functions,…):

Subscribe to the feed for: