想知道C语言怎么遍历文件内容找到指定字符串并将其替换为另一个指定字符串

[一拳_超人]

#include <stdio.h>
#include <stdlib.h>
#include <sting.h>
int replace(char * a,char * b);
int main(int argc,char * argv[])
{
    int i,len,len1 = 0,len2 = 0;
    char *a,*b;
    len1 = strlen(argv[3])
    len2 = strlen(argv[4])
    if(len1 > len2)
        len = len1;
    else len = len2;
    a = (char *)malloc(len+1);
    b = (char *)malloc(len+1);
    strcpy(a,argv[3]);
    a[len1+1] = '\0';
    strcpy(b,argv[4]);
    b[len2+1] = '\0';
    return 0;
}
int replace(char * a,char * b)
{
    FILE *f;
    f = fopen("C:\\Users\\xiaoy\\Desktop\\abo\\filename.txt","r");
    if( NULL == f )
    {
        printf("read file failed");
    }
    else {
        while()
    }
}

这是目前的代码，不知道如何遍历文件找到指定字符串计数并替换

[铖邑]

全部读入，找到指定的字符串，替换之后再全部输出到文件里面