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Path: news1.cris.com!news
From: [e-mail] (Aubrey Harrison)
Newsgroups: comp.lang.c
Subject: Re: C beginner needs your help ASAP
Date: 19 Feb 1996 12:14:34 GMT
Organization: Concentric Internet Services
Message-ID: <4g9pja$[e-mail]>
References: <4g862f$[e-mail]> <4g8ahd$[e-mail]> <danpop.824689489@rscernix>
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You are correct, I did realize these errors after I made the post. But 1. When
I  declared buf I had intended to use 4 digits but in the loop decided counting
to 10 was sufficient to show how sprintf worked, 2. Again, when I declared
filename I was going to use "data" plus four digits which is eight plus the
terminating null, 3. I stuck in the ".ext" as an after thought to show that it
could be done (if needed) and intended to comment it out and did in fact
overlook that filename was not big enough to hold it with the extra chars. Of
course it was a small program that was only used to show that sprintf was the
command he was looking for.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Aubrey Harrison    [e-mail]    [e-mail]
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What makes us so bitter against people who outwit us is that
they think themselves cleverer than we are.
               -Francois, Duc de La Rochefoucauld (1613-1680)
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In article <danpop.824689489@rscernix>, [e-mail] says...
>
>In <4g8ahd$[e-mail]> [e-mail] (Aubrey Harrison)
writes:
>
>>This is how I would do it. I tested it and it seems to do what you want. Of
>                                            ^^^^^^^^
>"It seems" is the keyword here, indeed.
>
>>course, I am no expert, in fact I was called "ignorant and idiot" by Mister
Dan
>
>Not only you're no expert, you have also difficulties counting up to ten.
>
>>#include <stdio.h>
>>
>>main()
>>{
>>        char buf[3],filename[9];
>>        int  i;
>>
>>        for(i=0; i<10; i++)
>>        {
>>                sprintf(buf,"%d",i);
>>                strcpy( filename,"data");
>>                strcat( filename, buf );
>>                strcat( filename, ".ext");
>
>strcat and strcpy are _not_ functions returning an int, hence a proper
>declaration is mandatory (even if the value returned is discarded).
>ALWAYS include <string.h> before using string manipulation functions.
>
>Anyway, these 4 lines can be replaced by a single sprintf call:
>
>                sprintf(buf, "data%d.ext", i);
>
>>                printf( "%s\n", filename);
>>        }
>Returning a value from a function (implicitly) defined as returning int
>is always a good idea.
>>}
>
>Let's look at how buf and filename are dimensioned.
>
>buf will always hold one digit and the terminating null character.  It's
>oversized by one character, but this not a major problem.  Better safe
>than sorry :-)
>
>OTOH, we're in deep trouble with filename, which will have to contain
>strings of the form "dataX.ext", but sizeof "dataX.ext" is 10, not 9.
>Now we're invoking undefined behaviour and we should be sorry for this :-)
>
>Too many mistakes in such a short and simple program, don't you think?
>Badly written code is of no help to anybody.  First learn C _yourself_,
>then try to help others.
>
>Dan
>--
>Dan Pop
>CERN, CN Division
>Email: [e-mail]
>Mail:  CERN - PPE, Bat. 31 R-004, CH-1211 Geneve 23, Switzerland

--
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Aubrey Harrison    [e-mail]    [e-mail]
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
What makes us so bitter against people who outwit us is that
they think themselves cleverer than we are.
               -Francois, Duc de La Rochefoucauld (1613-1680)
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=