Comment lire et écraser le fichier texte en C?

Je suggère toujours d'utiliser un autre fichier faire ces solutions KindDA.

1. Lire la ligne
2. Mettez x dans un nouveau fichier dans une ligne et la copie du reste de la ligne.
3. Faites ceci jusqu'à ce que vous obtenez EOF
4. retirer l'ancien fichier
5. renommer ce nouveau fichier

Essayez ceci out

#include<stdio.h>
#include<stdio.h>
#include<string.h>
int main()
{
    char buffer[500],read[50][50];
    FILE *fp=fopen("text.txt","r+");
    int line =1;
    while(fgets(buffer,500,fp)!=NULL){
        buffer[0]='x';
        printf("\n%d ",line);
        puts(buffer);
        strcat(read[line-1],(const char*)buffer);
        line++;
    }
    fclose(fp);
    FILE *fp1=fopen("text.txt","w");
    rewind(fp1);
    fprintf(fp1,"%s",read);
    return 0;
    }

// file_overwrite.cpp : main project file.
// File opens and write y value to a file
// again reads same file and re-writes y value to a file

#include "stdafx.h"

using namespace System;

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

int main(int argc, char *argv[])
{
    int x = 19530;

    FILE *fp1 = fopen("D:\\Data\\BUFF.txt","w+");

    if(fp1 == NULL)
        printf("File not opening \n");
        int y=x;
        fprintf(fp1, "%d \n", y);
        fclose(fp1);
        printf("\n file -> open -> write y value and close");


        freopen("D:\\Data\\BUFF.txt", "w", fp1);
        rewind(fp1);
        y=100;
        fprintf(fp1, "%d \n", y);
        printf("\n file -> Reopen -> rewind write y values and close");
        fclose(fp1);

       getch();
       return 0;
}

// overwrite_file.cpp 
// File opens and write y value to a file
// again reads same file and re-writes y value to a file

#include "stdafx.h"

using namespace System;

#include<stdio.h>
#include<stdio.h>
#include<string.h>                //Include appropriate headers
#include <conio.h>
#include<stdlib.h>

int main(int argc, char *argv[])
{
    int x = 19530;                            // Give any value in the limit

    FILE *fp1 = fopen("D:\\Data\\BUFF.txt","w+");   // open file to write

    if(fp1 == NULL)                                 // if the file pointer encounters a null, it may not open neither overwrite 
        printf("File not opening \n");
        int y=x;                                     
        fprintf(fp1, "%d \n", y);                   //print y
        fclose(fp1);
        printf("\n file -> open -> write y value and close");  // close the file after writing the value of y


        freopen("D:\\Data\\BUFF.txt", "w", fp1);            //reopen and rewind file 
        rewind(fp1);
        y=100;                                              // this value of y given within the limits gets printed on the .exe console
        fprintf(fp1, "%d \n", y);
        printf("\n file -> Reopen -> rewind write y values and close");    // rewind write values and close 
        fclose(fp1);

       getch();
       return 0;
}