# 系统编程(c库函数)

eg:fputs和fputc函数//c库函数

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

int main()
{
    FILE *fp=fopen("f1.txt","w");
    if(fp==NULL){
        printf("fopen error\n");
        return -1; 
    }   
#if 1
    char str[32]="welcome to shanghai";
    fputs(str,fp);//fputs读取整行字符
    fclose(fp);
#else
    fputc //fputc读取单个字符


#endif
}

eg: fpintf()和fscanf() //c库

#include<stdio.h>
#include<string.h>
typedef struct student
{
    char name[32];
    int age;
    char sex;
}STU;


int main()
{
#if 1
    int age;
    char name[32];
    char sex;
    FILE * fp=fopen("fprintf.txt","w");
    STU stu={"小明",21,'M'};
    fprintf(fp,"%s\t%d\t%c\t",stu.name,stu.age,stu.sex);
    fclose(fp);
#else
FILE *fp=fopen();


#endif
}

eg:fseek() ftell()

#include<stdio.h>
int main()
{
    FILE *fp=fopen("f3.txt","r");
    fseek(fp,0,SEEK_END);//指针偏移量,0:偏移一个字节,SEEK_END:从末尾开始偏移  -是往前移，+是往后移
    int ret=ftell(fp);//以文件首为参照物，指针现在的位置，返回值是从文件首到目前多少个字节
    printf("ret=%d\n",ret);
    fclose(fp);