读一行：

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
const int maxn  = 10;
int main()
{
    char s[1024] = {0};
    FILE *p = fopen("/home/exbot/wangqinghe/C/20190716/file.txt","r");
    
    //第一个参数是一个内存地址，第二个参数是这块内存的大小，
//第三个参数是fopen返回的文件指针
    fgets(s,maxn,p);
    printf(" s = %s\n",s);

    fclose(p);
    return 0;
}

读所有：

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
const int maxn  = 10;
int main()
{
    char s[1024] = {0};
    FILE *p = fopen("/home/exbot/wangqinghe/C/20190716/file.txt","r");
    //feof(p) p文件到尾部则返回正
    while(!feof(p))
    {
        memset(s,0,sizeof(s));
        fgets(s,sizeof(s),p);
        printf("%s\n",s);    
    }

    fclose(p);
    return 0;
}