Date: Mon, 30 Mar 2009 21:42:15 -0700 From: Gary Kline <kline@thought.org> To: Josh Carroll <josh.carroll@gmail.com> Cc: FreeBSD Mailing List <freebsd-questions@freebsd.org> Subject: Re: Why?? (prog question) Message-ID: <20090331044214.GA11129@thought.org> In-Reply-To: <8cb6106e0903302008j5ab06a97odbd32fb68c1a404d@mail.gmail.com> References: <20090331025726.GA10888@thought.org> <8cb6106e0903302008j5ab06a97odbd32fb68c1a404d@mail.gmail.com>
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On Mon, Mar 30, 2009 at 11:08:57PM -0400, Josh Carroll wrote:
> On Mon, Mar 30, 2009 at 10:57 PM, Gary Kline <kline@thought.org> wrote:
> > people, i've been under the weather for days and will probably be for a few more.
> > new and TEMPORARY meds dont like me, ugh.
> >
> > can anybody clue me in why the followin joinline program fails to catch if argc == 1?
> >
> >
> > /*
> > * simple prog to join all | very nearly all lines of a text file that
> > * make up one paragraph into one LONG line.
> > *
> > * paragraphs are delimiated by a single \n break.
> > */
> >
> > #include <stdio.h>
> > #include <string.h>
> > #include <stdlib.h>
> >
> > main(int argc, char argv[])
> > {
> > char buf[65536];
> >
> > if (argc == 1)
> > {
> > printf("Usage: %s < file > newfile\n", argv[0]);
> > exit (-1);
> > }
> > while (fgets(buf, sizeof buf, stdin) )
> > {
> > if (*buf == '\n')
> > {
> > fprintf(stdout, "\n\n");
> > }
> > else
> > {
> > buf[strlen(buf)-1] = ' ';
> > fputs(buf, stdout);
> > }
> > }
> > }
>
> main should be:
>
> int main(int argc, char **argv)
>
> or perhaps
>
> int main(int argc, char *argv[])
>
> As is, you're defining int as char argv[] (e.g. char *) instead of char **.
>
> What will likely happen is you'll get a segmentation fault when you
> try to run the program, since your printf format spec has %s, but
> you're passing it a char.
>
> In fact, if you compile it with -Wall, you'll see the two problems
> I've mentioned:
>
> t.c:13: warning: second argument of 'main' should be 'char **'
> t.c: In function 'main':
> t.c:20: warning: format '%s' expects type 'char *', but argument 2 has
> type 'int'
>
> Change char argv[] to char *argv[] or char **argv and it should work properly.
>
> Note also that your main should have an int return type and should
> return a value.
>
> Regards,
> Josh
you got it; as far as i know this is the first time that i've ever done the
"char argv[]" instead of the "char *argv[]".
thanks!
gary
:x
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--
Gary Kline kline@thought.org http://www.thought.org Public Service Unix
http://jottings.thought.org http://transfinite.thought.org
The 2.41a release of Jottings: http://jottings.thought.org/index.php
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