Thread: c codes need help,thanks

QUESTION:The following program reads from a text file containing numeric data stored in columns separated by one blank space. Write the code and compile it on your computer. Create a text file called myfile.txt containing a few columns (3×5 for example) of numeric data (real numbers) and test the program.
#include <stdio.h>
int main(void)
{
FILE *fp;
double val;
char ch;

fp = fopen("myfile.txt","r");
do{
fscanf( fp, "%lf", &val );
ch = getc(fp);
printf(" %lf",val);
if ( ch=='\n' || ch==EOF )
printf("\n");
} while ( ch != EOF );
fclose(fp);
return 0;
}
Analyse the code and include comment lines explaining how the program achieves its task. Modify the code so that the program additionally creates a new text file where it stores only the integer part (discard the factionary part) of the real numbers stored in myfile.txt. The new file should write data in the same format (3×5 with columns separated by space) as the original file. Include statements to check if the file was opened and closed successfully. Submit only the final, commented code.

Code:

#include <stdio.h>
int main(void)
{
	FILE *fp,*fw;// declaring file pointers.
	double val;
	char ch;
	int new;        
	if((fp = fopen("myfile.txt","r"))==NULL);
	{
	printf("sorry,cannot open the file\n");
	exit(0);
	}
    fw = fopen("mynewfile.txt","w");
	do{
		fscanf(fp, "%lf", &val); //read real number from the file.
		ch = getc(fp);           //get the following number after the realnumber.
		new=val;
		fprintf(fw,"%d",new);
		printf("%lf",val);    //print out the real number.
		printf("%d",new);      //print out the integer number.
		
		if ( ch=='\n' || ch==EOF )//determin to end the progress if there is a '\n' char or End Of File.
			printf("\n");  // switch to next line.
	}while ( ch != EOF );
	fclose(fp);
	return 0;
}

i am unsure how to get the integer part of real number.

10-2.c: In function ‘main’:
10-2.c:12: warning: incompatible implicit declaration of built-in function ‘exit’

the message return from compiler.

Originally Posted by Sebastiani

>> i am unsure how to get the integer part of real number.

math.h has a function floor( ) that does just that.

oops,that function is beyond my understanding~~

Originally Posted by matsp

Well, getc() is the wrong way!

If you have a floating point value from a calculation, how would you produce the integer part? I presume that file handling isn't the first part of your exercises in C? Maybe you need to look back into the chapters about data types, floating point in particular.



You need to include the header file that contains the function exit() - stdlib.h.

--
Mats

define a variable in integer form and print it out with the integer part?

cannot do that?

Originally Posted by matsp

What is it that you can not do? What does your current code look like, and what is the problem with it?

--
Mats

Code:

#include <stdio.h>
int main(void)
{
	FILE *fp,*fw;// declaring file pointers.
	double val;
	char ch;
	int new;        // new for integer part.
	if((fp = fopen("myfile.txt","r"))==NULL);
	{
	printf("sorry,cannot open the file\n");
	exit(0);
	}
    fw = fopen("mynewfile.txt","w");
	do{
		fscanf(fp, "%lf", &val); //read real number from the file.
		ch = getc(fp);           //get the following number after the realnumber.
		new=val;                 //pass numbers to integer form.cos new is defined intefer
		fprintf(fw,"%d",new);
		printf("%f",val);    //print out the real number.
		printf("%d",new);      //print out the integer number.
		
		if ( ch=='\n' || ch==EOF )//determin to end the progress if there is a '\n' char or End Of File.
			printf("\n");  // switch to next line.
	}while ( ch != EOF );
	fclose(fp);
	return 0;
}

appledemacbook:documents apple$ gcc 10-2.c
10-2.c: In function ‘main’:
10-2.c:12: warning: incompatible implicit declaration of built-in function ‘exit’

Originally Posted by matsp

If you read post #2, you will find the answer to why exit() is undeclared.

--
Mats

Code:

#include <stdio.h>
#include <stdlib.h>
int main(void)
{
	FILE *fp,*fw;// declaring file pointers.
	double val;
	char ch;
	int new;        // new for integer part.
	if((fp = fopen("myfile.txt","r"))==NULL);
	{
	printf("sorry,cannot open the file\n");
	exit(0);
	}
    fw = fopen("mynewfile.txt","w");
	do{
		fscanf(fp, "%lf", &val); //read real number from the file.
		ch = getc(fp);           //get the following number after the realnumber.
		new=val;                 //pass numbers to integer form.cos new is defined intefer
		fprintf(fw,"%d",new);
		printf("%f",val);    //print out the real number.
		printf("%d",new);      //print out the integer number.
		
		if ( ch=='\n' || ch==EOF )//determin to end the progress if there is a '\n' char or End Of File.
			printf("\n");  // switch to next line.
	}while ( ch != EOF );
	fclose(fp);
	return 0;
}

1.1 2.2 3.3 4.4 5.5
1.2 2.3 3.4 4.5 5.6
1.3 2.4 3.5 4.6 5.7


ye. the compiler is okay, but it cannot be run.
it cannot return any result when the command ./a.out

Originally Posted by matsp

Huh? Can you rephrase that, as I don't understant what you are asking for...

--
Mats

the compiler has not said the codes are wrong. but as the question asked i do,
the 3*5 matrix number are stored in myfile.txt
it cannot run when ues the program.
it was okay with the codes in the question.

i am useing macbook, gcc 4.2

does it matter?

Originally Posted by matsp

Look VERY carefully on this line:

Code:

	if((fp = fopen("myfile.txt","r"))==NULL);

Or, add "-Wall -Wextra" (without the quotes) to the gcc command-line, and it will actually tell you. That is generally a good idea anyways, as most fo the warnings you get from that will be more or less valid errors.

--
Mats

appledemacbook:documents apple$ -Wall -Wextra
-bash: -Wall: command not found


what is the matter? i am new to unix command.

i was use VS instead.

how to verify the codes with Mac OS X command terminal?
thanx



hth

Originally Posted by matsp

Erh, no. You want to use "gcc -Wall -Wextra [optionally other stuff] yourfile.c" to compile the code.

--
Mats

appledemacbook:documents apple$ gcc -Wall -Wextra [myfile.txt] 10-2.c
i686-apple-darwin9-gcc-4.0.1: [myfile.txt]: No such file or directory
10-2.c: In function ‘main’:
10-2.c:10: warning: empty body in an if-statement
appledemacbook:documents apple$ gcc -Wall -Wextra myfile.txt 10-2.c
10-2.c: In function ‘main’:
10-2.c:10: warning: empty body in an if-statement
ld warning: in myfile.txt, file is not of required architecture
appledemacbook:documents apple$


i do have state the if-statement.

Code:

if((fp = fopen("myfile.txt","r"))==NULL);

if the value of fopen is NULL, it will exit...