problem with sizeof in while loop reading a file

[lisp9000]

I wrote a small test program to read a file of data and print each
line, but it's only printing the 2nd line out of 3 total lines.

The test file, "foo.txt", has 3 lines:

7388: Zn->Z0 Run coward!
8473: Q1->P2 HAHAHAHAHA!
8381: G3->EVERYONE ok ok ok!

But when I run my progam it only prints the second line:

about to open file for reading
testing if fp stream was opened
entering while loop
about to call fgets
about to call printf
8473: Q1->P2 HAHAHAHAHA!

about to call fgets
about to call printf
closing file
about to exit

Also what does this warning mean and how can I eliminate it:
foo.c: In function 'main':
foo.c:33: warning: incompatible implicit declaration of built-in
function 'exit'

Here is my code:

#include <stdio.h>

int main(void)
{

FILE *fp;
char s[80];

printf("about to open file for reading\n");
fp = fopen("foo.txt" ,"r");
printf("testing if fp stream was opened\n");
if (fp != NULL)
{

printf("enterin g while loop\n");

while ( (fgets(s, sizeof(s), fp)) != NULL)
{
printf("about to call fgets\n");
fgets(s,sizeof( s),fp);
printf("about to call printf\n");
printf("%s\n",s );
}
}

printf("closing file\n");

fclose(fp);

printf("about to exit\n");

exit(0);

}

Lisp 9000

[Richard Tobin]

In article <11************ **********@r29g 2000hsg.googleg roups.com>,
li******@gmail. com <li******@gmail .comwrote:

while ( (fgets(s, sizeof(s), fp)) != NULL)

Here you call fgets, and don't print the result.

{
printf("about to call fgets\n");
fgets(s,sizeof( s),fp);

Here you call it again.

-- Richard
--
"Considerat ion shall be given to the need for as many as 32 characters
in some alphabets" - X3.4, 1963.

[lisp9000]

On Sep 14, 7:41 pm, rich...@cogsci. ed.ac.uk (Richard Tobin) wrote:

In article <1189813623.280 906.180...@r29g 2000hsg.googleg roups.com>,

lisp9...@gmail. com <lisp9...@gmail .comwrote:

while ( (fgets(s, sizeof(s), fp)) != NULL)

Here you call fgets, and don't print the result.

{
printf("about to call fgets\n");
fgets(s,sizeof( s),fp);

Here you call it again.

Oops. Thanks Richard. And what does this warning mean and how can I
eliminate it:
foo.c: In function 'main':
foo.c:33: warning: incompatible implicit declaration of built-in
function 'exit'

Lisp 9000

[CBFalconer]

"li******@gmail .com" wrote:

>
I wrote a small test program to read a file of data and print each
line, but it's only printing the 2nd line out of 3 total lines.

The test file, "foo.txt", has 3 lines:

7388: Zn->Z0 Run coward!
8473: Q1->P2 HAHAHAHAHA!
8381: G3->EVERYONE ok ok ok!

But when I run my progam it only prints the second line:

.... snip ...

>
Here is my code:

#include <stdio.h>

Where is #include <stdlib.h(for exit function)

>
int main(void) {
FILE *fp;
char s[80];

printf("about to open file for reading\n");
fp = fopen("foo.txt" ,"r");
printf("testing if fp stream was opened\n");
if (fp != NULL) {
printf("enterin g while loop\n");
while ( (fgets(s, sizeof(s), fp)) != NULL) {
printf("about to call fgets\n");

You just called fgets. eliminate this line.

fgets(s,sizeof( s),fp);

And this line. It just discards the line just read.

printf("about to call printf\n");
printf("%s\n",s );
}
}
printf("closing file\n");
fclose(fp);
printf("about to exit\n");
exit(0);

You could use "return 0" here in place of exit.

}

--
Chuck F (cbfalconer at maineline dot net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home .att.net>

--
Posted via a free Usenet account from http://www.teranews.com

[Jack Klein]

On Sat, 15 Sep 2007 00:32:54 -0000, "li******@gmail .com"
<li******@gmail .comwrote in comp.lang.c:

On Sep 14, 7:41 pm, rich...@cogsci. ed.ac.uk (Richard Tobin) wrote:

In article <1189813623.280 906.180...@r29g 2000hsg.googleg roups.com>,

lisp9...@gmail. com <lisp9...@gmail .comwrote:

while ( (fgets(s, sizeof(s), fp)) != NULL)

Here you call fgets, and don't print the result.

{
printf("about to call fgets\n");
fgets(s,sizeof( s),fp);

Here you call it again.

Oops. Thanks Richard. And what does this warning mean and how can I
eliminate it:
foo.c: In function 'main':
foo.c:33: warning: incompatible implicit declaration of built-in
function 'exit'

It means that you should include the standard header that prototypes
the exit() function, namely <stdlib.h>.

--
Jack Klein
Home: http://JK-Technology.Com
FAQs for
comp.lang.c http://c-faq.com/
comp.lang.c++ http://www.parashift.com/c++-faq-lite/
alt.comp.lang.l earn.c-c++
http://www.club.cc.cmu.edu/~ajo/docs/FAQ-acllc.html

[lisp9000]

On Sep 14, 9:19 pm, CBFalconer <cbfalco...@yah oo.comwrote:

>
Where is #include <stdlib.h(for exit function)

Oops, thought that was provided by <stdio.h:)

You just called fgets. eliminate this line.

....

And this line. It just discards the line just read.

Ah I see that now.

You could use "return 0" here in place of exit.

I was curious about that. How do you know when to use "return 0;" vs
"exit(0);" and does it make a difference?

Lisp 9000

[lisp9000]

On Sep 14, 11:37 pm, Jack Klein <jackkl...@spam cop.netwrote:

>
It means that you should include the standard header that prototypes
the exit() function, namely <stdlib.h>.

I'll keep that in mind next time. Thanks Jack.

comp.lang.chttp ://c-faq.com/

Did you write the C FAQ? The ASCII version on the website hasn't been
updated in 3 years. Is the FAQ static or will further updates be made?
Just curious.

Lisp 9000

[Flash Gordon]

li******@gmail. com wrote, On 15/09/07 07:52:

On Sep 14, 11:37 pm, Jack Klein <jackkl...@spam cop.netwrote:

>It means that you should include the standard header that prototypes
the exit() function, namely <stdlib.h>.

I'll keep that in mind next time. Thanks Jack.

>comp.lang.c http://c-faq.com/

Did you write the C FAQ? The ASCII version on the website hasn't been
updated in 3 years. Is the FAQ static or will further updates be made?
Just curious.

The authors details are on the site. The web version has been updated
fairly recently, the other versions have not.
--
Flash Gordon

[Joachim Schmitz]

<li******@gmail .comschrieb im Newsbeitrag
news:11******** *************@n 39g2000hsh.goog legroups.com...

On Sep 14, 9:19 pm, CBFalconer <cbfalco...@yah oo.comwrote:

<snip>

>You could use "return 0" here in place of exit.

I was curious about that. How do you know when to use "return 0;" vs
"exit(0);" and does it make a difference?

Inside "main" (and inside main only) "return" is equvalent to "exit". Slight
difference: "exit" is a function, so a propor prototy needs to be in scope
and it needs the (), "return" is a keyword and the () are optional.

Bye, Jojo

[Flash Gordon]

Joachim Schmitz wrote, On 15/09/07 10:05:

<li******@gmail .comschrieb im Newsbeitrag
news:11******** *************@n 39g2000hsh.goog legroups.com...

>On Sep 14, 9:19 pm, CBFalconer <cbfalco...@yah oo.comwrote:

<snip>

>>You could use "return 0" here in place of exit.

I was curious about that. How do you know when to use "return 0;" vs
"exit(0);" and does it make a difference?

Inside "main" (and inside main only) "return" is equvalent to "exit".

Unless main has been called recursively.

Slight
difference: "exit" is a function, so a propor prototy needs to be in scope
and it needs the (), "return" is a keyword and the () are optional.

Personally I use return from main.
--
Flash Gordon