«

Is getopt() and its companions, commonly found in GNU libc and other
Unices libc, part of the C standard?

Another doubt: I have a switch inside a while loop; is there a way to
break out of the loop from the switch without using goto? I mean:

start:
while(chr = fgetc(inputfile))
{
switch(chr)
{
case 'a': case 'b':
do_one_stuff(chr);
break;
case 'c': case 'd':
do_some_other_stuff(chr);
break;
case 'e': case 'f':
do_stuff(chr);
break;
default:
goto start;
} /* end switch */
do_even_more_stuff_here();
} /* end while */

Is there a way to get out of the while (i.e., skipping the
"do_even_more_stuff_here();" part) without using this goto?

Thank in advance.

--
Quidquid latine dictum sit altum viditur

José de Paula <> scribbled the following:
> Is getopt() and its companions, commonly found in GNU libc and other
> Unices libc, part of the C standard?

No.

> Another doubt: I have a switch inside a while loop; is there a way to
> break out of the loop from the switch without using goto? I mean:

> start:
> while(chr = fgetc(inputfile))
> {
> switch(chr)
> {
> case 'a': case 'b':
> do_one_stuff(chr);
> break;
> case 'c': case 'd':
> do_some_other_stuff(chr);
> break;
> case 'e': case 'f':
> do_stuff(chr);
> break;
> default:
> goto start;
> } /* end switch */
> do_even_more_stuff_here();
> } /* end while */

> Is there a way to get out of the while (i.e., skipping the
> "do_even_more_stuff_here();" part) without using this goto?

You could use some sort of flag that you set before the break, and
check before the do_even_more_stuff_here(). If the flag is true,
you can then break or continue the while loop.

--
/-- Joona Palaste () ------------- Finland --------\
\-- http://www.helsinki.fi/~palaste --------------------- rules! --------/
"Insanity is to be shared."
- Tailgunner

In other news, José de Paula <> typed:
> Another doubt: I have a switch inside a while loop; is there a way to
> break out of the loop from the switch without using goto? I mean:
>

I'd do:

> while(chr = fgetc(inputfile))
> {

int should_break_out = 0;

> switch(chr)
> {
> case 'a': case 'b':
> do_one_stuff(chr);
> break;
> case 'c': case 'd':
> do_some_other_stuff(chr);
> break;
> case 'e': case 'f':
> do_stuff(chr);
> break;
> default:

should_break_out = 1;
break;
> } /* end switch */

if( should_break_out )
break;

> do_even_more_stuff_here();
> } /* end while */
>
> Is there a way to get out of the while (i.e., skipping the
> "do_even_more_stuff_here();" part) without using this goto?
>

--
runtime

José de Paula wrote:

> Is getopt() and its companions, commonly found in GNU libc and other
> Unices libc, part of the C standard?
>

No, but it is part of POSIX (which is OT in this newsgroup).

> Another doubt: I have a switch inside a while loop; is there a way to
> break out of the loop from the switch without using goto? I mean:
>
> start:
> while(chr = fgetc(inputfile))
> {
> switch(chr)
> {
> case 'a': case 'b':
> do_one_stuff(chr);
> break;
> case 'c': case 'd':
> do_some_other_stuff(chr);
> break;
> case 'e': case 'f':
> do_stuff(chr);
> break;
> default:
> goto start;
> } /* end switch */
> do_even_more_stuff_here();
> } /* end while */
>
> Is there a way to get out of the while (i.e., skipping the
> "do_even_more_stuff_here();" part) without using this goto?
>

What you really want is not break out of the while, but continue (since you
say goto start which is the start of the while loop). A continue will work
just fine as it doesnt have special meaning inside the switch.

If you really want to break out of the while loop, no real easy and elegant
way. You'll have to maintain a possibly useless separate flag and
unnecessarily check it as part of your while condition. A goto might be
cleaner and efficient. Don't be dogmatic in rejecting programming
constructs.

-nrk.

> Thank in advance.
>

--
Remove devnull for email

José de Paula <> spoke thus:

> while(chr = fgetc(inputfile))

Aside from what others have said, this is incorrect: fgetc() returns
EOF if it fails (whether because of EOF or an error), and you should
test chr against it explicitly. I do hope chr is declared as an int,
by the way.

--
Christopher Benson-Manica | I *should* know what I'm talking about - if I
ataru(at)cyberspace.org | don't, I need to know. Flames welcome.

In <bvdqhf$gfi$> Joona I Palaste <> writes:

>José de Paula <> scribbled the following:
>> Is getopt() and its companions, commonly found in GNU libc and other
>> Unices libc, part of the C standard?
>
>No.

But it can be implemented in standard C and used anywhere a standard C
implementation is available.

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email:

On 2004-01-30, nrk <> wrote:
> José de Paula wrote:
>
>> Is getopt() and its companions, commonly found in GNU libc and other
>> Unices libc, part of the C standard?
>>
>
> No, but it is part of POSIX (which is OT in this newsgroup).
>

>><snip goto meaning "continue">

>
> What you really want is not break out of the while, but continue (since you
> say goto start which is the start of the while loop). A continue will work
> just fine as it doesnt have special meaning inside the switch.

Yes, what I want is continue, thanks. So in this case I could just use
continue? It feels counter-intuitive, because I'm used to the fact that,
syntactically (sp?), break and continue are the same thing, even though
continue doesn't have any meaning inside switch blocks.

>
> If you really want to break out of the while loop, no real easy and elegant
> way. You'll have to maintain a possibly useless separate flag and
> unnecessarily check it as part of your while condition. A goto might be
> cleaner and efficient. Don't be dogmatic in rejecting programming
> constructs.

Yeah, sure. In this case I don't see the goto as a big problem, because
the label is near the goto, and it's clear what the code does. I rather
prefer it than using the extra variable.

--
Quidquid latine dictum sit altum viditur

José de Paula wrote:

> On 2004-01-30, nrk <> wrote:
>> José de Paula wrote:
>>
>>> Is getopt() and its companions, commonly found in GNU libc and other
>>> Unices libc, part of the C standard?
>>>
>>
>> No, but it is part of POSIX (which is OT in this newsgroup).
>>
>
>>><snip goto meaning "continue">
>
>>
>> What you really want is not break out of the while, but continue (since
>> you say goto start which is the start of the while loop). A continue
>> will work just fine as it doesnt have special meaning inside the switch.
>
> Yes, what I want is continue, thanks. So in this case I could just use
> continue?

Yes.

> It feels counter-intuitive, because I'm used to the fact that,
> syntactically (sp?), break and continue are the same thing, even though
> continue doesn't have any meaning inside switch blocks.
>

Well, break and continue are not the same thing at all semantically. One
takes you out of the loop while the other just skips the rest of the code
for the current iteration of the loop. I agree with you on the
counter-intuitive part, as I also see break/continue as a pair that often
go together. The problem probably stems from a lazy compiler writer in the
early days who decided to re-use break for a somewhat similar purpose
instead of introducing a new keyword for use inside switch statements

See Chris Torek's excellent recent post on switch statements for a peek
under the hood:
<>

-nrk.

>>
>> If you really want to break out of the while loop, no real easy and
>> elegant
>> way. You'll have to maintain a possibly useless separate flag and
>> unnecessarily check it as part of your while condition. A goto might be
>> cleaner and efficient. Don't be dogmatic in rejecting programming
>> constructs.
>
> Yeah, sure. In this case I don't see the goto as a big problem, because
> the label is near the goto, and it's clear what the code does. I rather
> prefer it than using the extra variable.
>

--
Remove devnull for email

José de Paula <> wrote in message news:<>...
> Is getopt() and its companions, commonly found in GNU libc and other
> Unices libc, part of the C standard?

Can someone post some working code snippet using getopt()?

Thanks,
Nimmi

Em Fri, 30 Jan 2004 15:01:42 -0800, Nimmi Srivastav escreveu:

> José de Paula <> wrote in message news:<>...
>> Is getopt() and its companions, commonly found in GNU libc and other
>> Unices libc, part of the C standard?
>
> Can someone post some working code snippet using getopt()?
>
As you wish:

char ch, *flag1, *flag2;
while ( (ch = getopt(argc, argv, "o:f:h")) != -1)
{
switch (ch)
{
case 'o':
flag1 = optarg;
break;
case 'f':
flag2 = optarg;
break;
case 'h':
usage(stdout, EXIT_SUCCESS, argv[0]);
break;
case '?':
default:
usage(stderr, EXIT_FAILURE, argv[0]);
break;
}
}

Here optarg is a global variable defined by libc; it contains the argument
for the option. If you are under a Unix system (*BSD, Linux et al.), man 3
getopt should enlighten you. However, as pointed elsewhere in this thread,
getopt() is not portable outside Unix systems.

--
Quidquid latine dictum sit altum viditur