从读取文件中修改第一个数字 c 语言

Question

int main()
{

 FILE *file=fopen("numbers.dat","rb");

    int number;

    if(file ==NULL)
        exit(0);
    while(fread(&number,sizeof(int),1,file))
        printf("%d",number);


return 0 ;

}

Answer 1

The code below opens a file in read/write bytes mode and writes a number to the beginning of the file without erasing its content, is that what you need?

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

int main () {
   FILE * fp;
   int a = 12;

   fp = fopen ("titi", "rb+");
   fwrite(&a, sizeof(int), 1, fp);
   fclose(fp);
   return(0);
}

If you want to read it first, you might want to look at the fseek() function to place your file cursor back at the beginning of the file or open the file twice, once to read it and once to write to it.