Problem Editing A Text File In C

[jursnamo]

Hay all
i have a problem editing a text file in c

this is code

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


typedef struct
{
    char *name;
    float gpa;
}student;


int main()
{
    FILE *originalFile = fopen("C:\\Users\\jurs\\Desktop\\students.txt","r");
    FILE *newFile = fopen("C:\\Users\\jurs\\Desktop\\students_temp.txt","w");


    int studentCount;
    fscanf(originalFile, "%i", &studentCount);


    student *passingStudents = malloc(sizeof(student) * studentCount);


    int passingCount = 0;
    for (int i = 0; i < studentCount; i++)
    {
        int namelen;


        fscanf(originalFile, "%i", &nameLen);


        char *name = malloc(sizeof(char) * (nameLen + 1));
        name[nameLen] = '\0';
        float gpa;


        fscanf(originalFile, "%s %f", name, &gpa);


        if (gpa >=65.0)
        {
            passingStudents[passingCount].name = name;
            passingStudents[passingCount].gpa = gpa;


            passingCount++;
        }
    }


    fprintf(newFile, "%i\n",passingCount);


    for (int i = 0; i < passingCount; i++)
        fprintf(newFile, "%i %s %.2f\n", strlen(passingStudents[i].name, pasiingStudents[i].gpa));






    fclose(originalFile);
    fclose(newFile);


    remove("C:\\Users\\jurs\\Desktop\\students.txt");
    rename("C:\\Users\\jurs\\Desktop\\students_temp.txt" , "C:\\Users\\jurs\\Desktop\\students.txt");


    printf("berhasil menghapus semua failing Students.")
    return 0;
}

erorr in

for (int i = 0; i < studentCount; i++)

please help me Master i'm newbie in C


Post the exact error

C:\Users\jurs\Desktop\tugas.c||In function `main':|C:\Users\jurs\Desktop\tugas.c|22|error: 'for' loop initial declaration used outside C99 mode|
C:\Users\jurs\Desktop\tugas.c|26|error: `nameLen' undeclared (first use in this function)|
C:\Users\jurs\Desktop\tugas.c|26|error: (Each undeclared identifier is reported only once|
C:\Users\jurs\Desktop\tugas.c|26|error: for each function it appears in.)|
C:\Users\jurs\Desktop\tugas.c|45|error: redefinition of 'i'|
C:\Users\jurs\Desktop\tugas.c|22|error: previous definition of 'i' was here|
C:\Users\jurs\Desktop\tugas.c|45|error: 'for' loop initial declaration used outside C99 mode|
C:\Users\jurs\Desktop\tugas.c|46|error: `pasiingStudents' undeclared (first use in this function)|
C:\Users\jurs\Desktop\tugas.c|46|error: too many arguments to function `strlen'|
C:\Users\jurs\Desktop\tugas.c|57|error: syntax error before "return"|
||=== Build finished: 10 errors, 0 warnings (0 minutes, 1 seconds) ===|

[Uli]

I think it is better if you initialize your variable name and type very first (before other statement). And you have to put your int i on the top (not in for stucture).

[c99tutorial]

Your first error means you have to enable C99 standard

C:\Users\jurs\Desktop\tugas.c||In function `main':|C:\Users\jurs\Desktop\tugas.c|22|error: 'for' loop initial declaration used outside C99 mode

It depends on the compiler on how to do this. With gcc you add "-std=gnu99" or "-std=c99" to the compiler flags.

[hk_mp5kpdw]

You are leaking memory. If the current student you are looking at does not have a passing grade, you skip assigning it to a slot in your passingStudents array. When this happens, you do nothing with the memory allocated for name and you lose track of it when moving on to processing the next student. You should be calling free on the name field whenever the student does not have a passing grade and at the end of your program calling free on both the name field for all locations within the passingStudents array with a valid student followed by a final call to free on the array itself.

int passingCount = 0;
for (int i = 0; i < studentCount; i++)
{
    ... 
    
    char *name = malloc(sizeof(char) * (nameLen + 1));
    name[nameLen] = '\0';
    
    ...
 
    if (gpa >=65.0)
    {
        ...
    }
    else
    {
        free(name);
    }
}

...


// At end loop through the passingStudents array and free the name member
for(int i = 0; i < passingCount; ++i )
{
    free(passingStudents[i].name);
}
// Then after that free the array itself
free(passingStudents);

---

Then you have this:

for (int i = 0; i < passingCount; i++)
    fprintf(newFile, "%i %s %.2f\n", strlen(passingStudents[i].name, pasiingStudents[i].gpa));

Your call to strlen is wrong here and it looks like there is only two arguments that you are actually passing to be printed when there should be 3: strlen(passingStudents[i].name), passingStudents[i].name and passingStudents[i].gpa (notice the misspelled pasiingStudents).