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Date: Mon, 11 Sep 2006 17:57:26 +0530
From: "Amarendra Godbole" <amarendra.godbole@gmail.com>
To: freebsd-questions@freebsd.org
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Subject: Sequence of execution of getopt() and usage()...
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Hi,

This is a general FreeBSD source related question, and I am posting it
here, as it did not fit in any other FreeBSD lists...

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):

int
main(int argc, char *argv[])
{
...
        while ((ch = getopt(argc, argv, "HLPRXfghorstuvwx")) != -1)
...
        if (argc < 2)
                usage();
...
}

Can't we check for the number of arguments *before* calling getopt()?
Something like:

int
main(int argc, char *argv[])
{
...
        if (argc < 2)
                usage();
...
        while ((ch = getopt(argc, argv, "HLPRXfghorstuvwx")) != -1)
...
}


This might make it a bit more efficient, though I don't have numbers'
to prove this.

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!

Best,
Amarendra