Thread: Program to find two consecutive numbers from a text file.

The program is working but if anyone know more efficient ways please let me know.

Side question about strings.

Why i need to use

char * string[100] and i can´t use char * string ?

Text File:
DIM: 4
Linha0: 12 4 60 60
Linha1: 3 7 3 5
Linha2: -56 31 31 12
Linha3: 34 -33 2 4

Code:

#include <stdio.h>
#include <stdlib.h>


int main(int argc, char** argv) {


    FILE *pFile = fopen("ex1.txt", "rt");


    char * string[100];
    int size;
    int numbers[4];


    if (pFile) {
        // To consume the 1 line
        fscanf(pFile, "%s %d", string, &size);


        // To consume  the others lines
        while (fscanf(pFile, "%s %d %d %d %d", string, &numbers[0], &numbers[1], &numbers[2], &numbers[3]) == 5) {
            for (int i = 0; i < size - 1; i++) {
                if (numbers[i] == numbers[i + 1])
                    printf("The numbers %d %d, are equals\n", numbers[i], numbers[i + 1]);
            }
        }

    } else {
        printf("Error opening the file");
    }
        fclose(pFile);

    return (EXIT_SUCCESS);
}

Great great...

I really "hate" Netbeans, this semester they force us to use that compiler because the C99 Standard but even the teachers don´t know very well to work with Netbeans.

I already use Visual Studio a little before, and i was really missing the -Wall, now i already activated.

Other thing i really hate at netbeans sometimes my code is 100% i make some correction lots of code go to red, and then the red only go away after i need rebuild the code again...

And some other minors things.

What program you recommend to code ?

Originally Posted by Salem

Are you compiling with -Wall yet?

Code:

$ gcc -Wall foo.c
foo.c: In function ‘main’:
foo.c:18:23: warning: format ‘%s’ expects argument of type ‘char *’, but argument 3 has type ‘char **’ [-Wformat=]
         fscanf(pFile, "%s %d", string, &size);
                       ^
foo.c:22:30: warning: format ‘%s’ expects argument of type ‘char *’, but argument 3 has type ‘char **’ [-Wformat=]
         while (fscanf(pFile, "%s %d %d %d %d", string, &numbers[0], &numbers[1], &numbers[2], &numbers[3]) == 5) {
                              ^

It only 'works' because you're lucky enough that "char * string[100]" allocates probably 400 or 800 bytes of memory for you to play with.

> char * string[100] and i can´t use char * string ?
Because char *string by itself doesn't point to any useful memory.

Try

Code:

char string[100];

or

Code:

char *string = malloc(100);

I am try to transform the program into a generic one, so the matrix could be DIM 2 or DIM 10 for example.

But i am not see what function should i use.

I was trying with sscanf but with start always from the begin of the buffer each time i use it.

Code:

#include <stdio.h>
#include <stdlib.h>
#define LENGTH 100


int main(int argc, char** argv) {


    FILE *pFile = fopen("ex1.txt", "rt");


    char buffer[LENGTH];
    int * vector;
    size_t size;
    
    if (pFile != NULL) {
        
        fgets(buffer, sizeof (buffer), pFile);
        sscanf(buffer, "%*s %d", &size); // %*s - Consume and throw away, and get the size of the matrix
        
        vector = malloc(sizeof (int) * size);


        while (fgets(buffer, sizeof (buffer), pFile)) {
            sscanf(buffer, "%*s"); 


            for (int i = 0; i < size; i++) {
                sscanf(buffer, "%d", &vector[i]);
                printf("%d \n", vector[i]); // Only prints garbage
            }
        }


        fclose(pFile);
        return (EXIT_SUCCESS);
    }
}

Working but what a mess...

Code:

        while (fgets(buffer, sizeof (buffer), pFile)) {
            char *p = buffer;

            while (*p) {
                if (isdigit(*p) && (*(p + 1)) != ':') {
                    long value = strtol(p, &p, 0); // 
                    printf("%ld\n", value);
                } else {
                    p++;
                }
            }
        }

Originally Posted by Salem

So your numbers are not actually separated by : then.

Code:

int lineNum, numChars;
if ( sscanf(buffer,"Linha%d:%n",&lineNum,&numChars) == 1 ) {  // %n does NOT count as a conversion
   char *p = buffer + numChars;
   // now you can walk the line using a much simpler strtol loop
}

Finally working... Thanks a million.

Still going to need to read about strtol when i got some time.

I still didn't yet grasp the concept of it the endptr parameter.

strtol - C++ Reference.

Code:

#include <stdio.h>
#include <stdlib.h>
#define LENGTH 100


int main(int argc, char** argv) {


    FILE *pFile = fopen("ex1.txt", "rt");


    char buffer[LENGTH];
    int * vector;
    size_t size;


    if (pFile != NULL) {


        fgets(buffer, sizeof (buffer), pFile);
        sscanf(buffer, "%*s %d", &size); // %*s - Consume and throw away, and get the size of the matrix


        vector = malloc(sizeof (int) * size);


        int lineNum, numChars;
        int value;
        int count = 0;
        while (fgets(buffer, sizeof (buffer), pFile)) {
            if (sscanf(buffer, "Linha%d:%n", &lineNum, &numChars) == 1) { // %n does NOT count as a conversion, it counts the numbers of caracters https://stackoverflow.com/questions/3401156/what-is-the-use-of-the-n-format-specifier-in-c
                char *p = buffer + numChars;                


                while ((value = strtol(p, &p, 0)) && errno == 0) {
                    vector[count] = value;
                    count++;
                }
                count = 0;
              
                for (int i = 0; i < size - 1; i++) {
                    if (vector[i] == vector[i + 1])
                        printf("The numbers %d %d, are equals\n", vector[i], vector[i + 1]);
                }
            }
        }


        free(vector);
        fclose(pFile);
        return (EXIT_SUCCESS);
    }
}