C Programming File I/O - c

Question

I'm trying to read from a text file and write to one, but every time I execute my code, nothing happens with the text files. By "nothing happens", I mean that the program won't read my input file and no data is exported into my output file. Could someone point out why it is not working? Thanks for any help given in advance. Here is my code:
#include <stdio.h>
#include <stdlib.h>
FILE *inptr, *outptr;
int main() {
int a, b, c;
inptr = fopen("trianglein.txt","r"); //Initialization of pointer and opening of file trianglein.txt
outptr = fopen("triangleout.txt","w"); //Initialization of pointer and opening of file triangleout.txt
while((fscanf(inptr,"%d %d %d",&a, &b, &c))!= EOF){
fprintf(outptr,"\n%2d %2d %2d\n",a,b,c);
if(a+b>c && b+c>a && c+a>b){
fprintf(outptr, "This is a triangle.\n");
if(a !=b && b !=c && a!=c){
fprintf(outptr, "This is a scalene triangle.\n");
if(a==b && a==c && c==b){
fprintf(outptr, "This is an equilateral triangle.\n");
if(a*a+b*b==c*c || b*b+c*c==a*a || a*a+c*c==b*b){
fprintf(outptr, "This is a right trianlge.\n");
}
}
}
}
}
return 0;
}
trianglein.txt contents:
10 12 15
2 3 7
3 4 5
6 9 5
6 6 6
6 8 10
7 7 9

Answer 1

Multiple problems.
Firstly, you need to check if inptr and outptr are valid by testing against NULL.
Secondly, fscanf can return either EOF, 0 or > 0.
If your input file doesn't contain valid input.
Also there are problems in that you can get 3 ints read successfull, or 2 ints or 1 and the value of a, b and c are only optionally set.
If no conversion took place on the input then the value of zero is returned in which case the while loop will exit.
Also bear in mind that with the scanf style functions this input will succeed and return the value of 1.
"1rubbish"
I think what you may want is something like the following:
// Somewhere near the top
#include <stderr.h>
// ... other includes
const char* inname = "trianglein.txt";
const char* outname = "triangleout.txt";
// Any other stuff
// Inside main...
// Initialization of pointer and opening of file trianglein.txt
if ((inptr = fopen(inname,"r")) == 0){
fprintf(stderr, "Error opening file %s: %s", inname, strerror(inname));
return -1;
}
// Initialization of pointer and opening of file triangleout.txt
if ((outptr = fopen(outname,"w")) == 0){
fprintf(stderr, "Error opening file %s: %s", outname, strerror(outname));
return -1;
}
int result;
while(true){
result = fscanf(inptr,"%d %d %d",&a, &b, &c);
if (result == EOF)
break;
if (result < 3) // Ignore incomplete lines
continue;
// do the normal stuff
}

Answer 2

Your program is working fine in my system. I use Code::Blocks 10.05 on Windows 7.
The only possibility of a logical error occurs when you have the file trianglein.txt with less than 3 integer values to be read by the fscanf(). For example trianglein.txt file with values 1, 1 2, 1 2 3 4, 1 2 3 4 5 etc. will give incorrect values to the variables b and/or c. So initialize a=-1, b=-1, c=-1 before the execution of each iteration of the loop and check them after reading.
If you are running the program check the file triangleout.txt for access rights. Some times you may not have write access on that particular file.
By the way the classification logic is wrong. An equilateral triangle can not be a right angled one.

Answer 3

Try putting
fclose(inptr);
and
fclose(outptr);
at the end of your code.

Answer 4

EDIT: As suggested by icktoofay, this answer is wrong.
You have to do fclose() or fflush() in order to get the data written to the file.
Insert these code right before return 0;
fclose(inptr);
fclose(outptr);