It's a 10 seconds trick that did the job and did not require recompiling.
EDIT: seeing how it has been downvoted, IMHO hacking is all about time and effectiveness. if you believe fixing ls print formats is such a crucial problem that it requires more than seconds of your time, we have different values.
Feel free to support the argument by showing your skills and improving the example.
You are entirely missing the point of this whole thing.
It is exactly about showing how hard it is to get a trivial change right in every detail. Your 10 second hack is what is wrong with 10 second hacks in general and even with most real solutions that are not carefully thought out.
It's not only that the devil is in the details it is all details. And you need to get all of them right, not just the current subset of the problem that you happen to be working on.
While I think that is the point, I don't know if was the author's originally intended point. You see 'hacking it' would imply just getting it to work, I expected to see something, well hackish, like replace the format specifier with %s and then wrap the number in a function call to something which read an environment variable to figure out how to print the number. That would be a hack, what Greg is doing is engineering a change to ls(1) which allows for pretty printing the numbers. So to my way of thinking the title is wrong, it sets the expectation of a hack and leads to an engineering exercise.
I think that's reflective of how experience levels change your perspective on how to approach a problem.
Someone with command line experience that is mostly a user of system utilities would think passing the output of ls through a filter is the way to go whereas someone with C experience that already has insight in how Unix is architected would do something more along the lines of what the author is doing. That's pretty much how unix got built to begin with, and probably both parties would qualify their solution as a 'hack'.
"Hacker" has many meanings. A quick read of the Wikipedia entry for the term shows you that. RFC 1392 defines a hacker as "A person who delights in having an intimate understanding of the internal workings of a system, computers and computer networks in particular." The only way to tell which definition is in use is via context, and for this case the meaning is unambiguously aligned with the RFC 1392 definition.
(Note that this RFC comes from the days when 'hacker' was becoming a widespread term for someone who breaks into computer systems; the RFC attempts to distinguish between a 'hacker' and a 'cracker.')
EDIT: seeing how it has been downvoted, IMHO hacking is all about time and effectiveness. if you believe fixing ls print formats is such a crucial problem that it requires more than seconds of your time, we have different values.
Feel free to support the argument by showing your skills and improving the example.