通过其他功能更新文件指针

#include<stdio.h>

void hello(FILE * fp)
{ 
    if( ( fp = fopen("log","r") ) == NULL)
        printf("%s", "Error opening file");
}

void main()
{
    char p;
    FILE *sf=fopen("prac.txt","r");
    hello(sf);

    p=fgetc(sf);
    printf("%c",p);
}
#include<stdio.h>

void hello(FILE * fp)
{