Sequence of execution of getopt() and usage()...

[Chuck Swiger]

On Sep 11, 2006, at 5:27 AM, Amarendra Godbole wrote:
> This is a general FreeBSD source related question, and I am posting it
> here, as it did not fit in any other FreeBSD lists...

This list is a quite reasonable choice to ask such questions.  :-)

> While browsing through sources for different userland utilities (cat,
> chmod, and so on), I noticed that in main(), first getopt() is called
> in a while loop, and then the check for the number of arguments passed
> is done. Something like this (from chmod.c):
[ ... ]
> Can't we check for the number of arguments *before* calling getopt()?
[ ... ]
> I observe a similar pattern in other utilities too - which might mean
> that there was a sound reason as to why it was done this way. Can
> someone be kind enough to explain this? Thanks in advance!

Sure.  The issue is that utilities which require a certain number of  
arguments do not want to count the option flags being passed in, but  
argc's count includes these flags and any values being passed to  
flags which take a value (ie, getopt() options followed by a colon ":").

It's much easier to process the options and then do "argc -= optind",  
and then determine whether the remaining # of arguments left meet the  
criteria for the particular program.

-- 
-Chuck