在while循环中使用fscanf和fprintf进行读写

Question

EDIT: With the help of members here I have updated my code. I am currently trying to solve why the while loop never detects the EOF.

I don't need an increment counter for [i] in my function returnStats(). I found this interesting and I can't seem to figure out why.

Specifically in the while loop which scans until the End of file. How does the program know to move to the next element of the array?

Also, since i is no longer a counter I can't use it to keep count so I used j along with j++.

My program details are as follows:

#include <stdio.h>

// function prototypes
void loadTextFile();
void returnStats();

// begin main function
int main(void){

    loadTextFile();
    returnStats();

    return 0;
} // end main function

// function which returns the number of entries, average, and maximum of the numbers read
void returnStats(){

    FILE *file = fopen("question5.txt","r");

    if(file == NULL)
    {
        printf("question3.dat cannot be opened!\n");
        fprintf(stderr, "Error opening the fil!\n");
    }

    else
        printf("\nquestion3.dat was opened successfully for reading.\n\n");

    int i=0, j=0; 
    int numbers[4];
    float average=0.0;
    int max=0;

    while(fscanf(file, "%d", &numbers[i]) != EOF) 
    {
        printf("%d was read from .txt file\n", numbers[i]);
        average += numbers[i];  

        if(numbers[i]>max)
            max = numbers[i];

        j++;    

    }   

    printf("\nThe number of entries is: %d", j);    
    printf("\nThe average of the numbers is: %.2f", average/4);
    printf("\nThe maximum of the numbers is: %d", max);

    fclose(file);

} // end returnAverage


// function to load the .txt file with array values so we may execute main on any computer. 
void loadTextFile(){

    FILE *file = fopen("question5.txt","w");

    if(file == NULL)
    {
        printf("question3.dat cannot be opened!\n");
        fprintf(stderr, "Error opening the fil!\n");
    }

    else
        printf("question3.dat was opened successfully for writing.\n");

    int numberArray[4]={56, 23, 89, 30};

    int i=0;

    for(i=0;i<4;i++)
    {
        fprintf(file, "%d\n", numberArray[i]);

    }

    printf("\nThe data was successfully written\n");

    fclose(file);
} // end function loadTextFile

Code Re-work

#include <stdio.h>

// function prototypes
void loadTextFile(FILE *file);
void returnStats(FILE *file);

// begin main function
int main(void){

    FILE *text = fopen("question6.txt","w");

    if(text == NULL)
    {
        printf("question6.dat cannot be opened!\n");
        fprintf(stderr, "Error opening the fil!\n");
    }

    else
        printf("\nquestion6.dat was opened successfully for Writing.\n\n");

    loadTextFile(text);
    returnStats(text);

    fclose(text);

    return 0;
} // end main function

// function which returns the number of entries, average, and maximum of the numbers read
void returnStats(FILE *file){


    int i=0;
    int number[4];

    while(fscanf(file, "%d", &number[i]) != EOF)
    //for (i=0;i<4;i++)
    {   
    //  fscanf(file, "%d", &number[i]);
        printf("\n%d : Was Read from the File\n", number[i]);
        fprintf(file, "%d\n", number[i]+10);
    }

} // end returnStats

// function to load the .txt file with array values so we may execute main on any computer. 
void loadTextFile(FILE *file){


    int numberArray[4]={56, 23, 89, 30};

    int i=0;

    for(i=0;i<4;i++)
    {
        fprintf(file, "%d\n", numberArray[i]);
        printf("\n%d : was written to the file\n", numberArray[i]);

    }

    printf("\nThe data was successfully written\n");

} // end function loadTextFile

Answer 1

you do not need to increment the position, bacause you dont need array for this. Your program uses just the first item of the array. So it replaces old value by new one prom the file. But you have just last value in the memory.

Answer 2

Simple solution if it doesn't harm is to append some string at the end of output in child/client process like “\\nend of output\\n”. I am not sure if fflush() can help or just give it a try