C语言实现文件操作实例(简单图示讲解)

struct _iobuf {
    char *_ptr;
    int  _cnt;
    char *_base;
    int  _flag;
    int  _file;
    int  _charbuf;
    int  _bufsiz;
    char *_tmpfname;
   };
typedef struct _iobuf FILE;//就是一个结构体类型的FILE，规定的文件的 所有信息，都是可以存储在上面

//打开文件
FILE * fopen ( const char * filename, const char * mode );//返回文件类型
//关闭文件
int fclose ( FILE * stream );//返回整型

//这是fgetc函数，可以理解为得到文件中的一个字符
int main()
{
	FILE* pf = fopen("test.txt", "r");
	for (int i = 0; i < 10; i++) {
		char src = fgetc(pf);
		printf("%c", src);
	}
	fclose(pf);
	pf = NULL;
	return 0;
}
//这是fputc函数，可以理解为放置文件中一个字符
int main()
{
	FILE* pf = fopen("test.txt", "w");
	for (int i = 0; i < 26; i++) {
		fputc('a' + i, pf);
	}
	fclose(pf);
	pf = NULL;
	return 0;
}

//fgets函数
int main()
{
	FILE* pf = fopen("test.txt", "r");
	char arr[20];
	while (fgets(arr, 20, pf) != NULL) {
		printf("%s", arr);
	}
	fclose(pf);
	pf = NULL;
	return 0;
}
//fputs函数
int main()
{
	FILE* pf = fopen("test.txt", "w");
	char arr[20];
	fputs("hello world!!\n", pf);
	fputs("hello why\n", pf);
	fputs("hello fzx\n", pf);
 
	fclose(pf);
	pf = NULL;
	return 0;
}

struct S {
	char name[20];
	int age;
	double score;
};
//fscanf格式化读取pf流中的数据，赋值给后面的参数，和scanf用法差不多，
//只是多一个FILE*类型，后面于scanf用法一致，改用&就用
int main()
{
	FILE* pf = fopen("test.txt", "r+");
	//读写都行
	//格式化输出
	//struct S s = { "why",19,100 };
	struct S s = {0};
	struct S s1 = { 0 };
	fscanf(pf, "%s %d %lf\n", s.name, &(s.age), &(s.score));
	printf("%s %d %lf\n", s.name, (s.age), (s.score));
	//fscanf(pf, "%s %d %lf\n", s1.name, &(s1.age), &(s1.score));
	//printf("%s %d %lf\n", s1.name, (s1.age), (s1.score));
	int a = 10;
	/*fscanf(pf, "%d", a);
	printf("%d\n", a);*/  //这是进行测试如果没有相应的数据读取的时候，不会报错，只是相当于没有这一行代码，不会发生任何改变（对相应a）
	fclose(pf);
	pf = NULL;
	return 0;
}
 
//这是fprintf函数的使用
int main()
{
	FILE* pf = fopen("test.txt", "r+");
	//读写都行
	//格式化输出
	struct S s = { "why",19,100 };
	fprintf(pf, "%s %d %lf\n", s.name, (s.age), (s.score));
	//printf("%s %d %lf\n", s.name, (s.age), (s.score));
	fclose(pf);
	pf = NULL;
	return 0;
}

struct S {
	char name[20];
	int age;
	double score;
};
//先写入二进制文件	fwrite
int main()
{
	struct S s = { "fzx",18,100 };
	FILE* pf = fopen("test.txt", "wb");
	//写一个二进制文件
	fwrite(&s, sizeof(struct S), 1, pf);
 
	fclose(pf);
	pf = NULL;
	return 0;
}
//再读取二进制文件 fread
int main()
{
	struct S s = { 0 };
	FILE* pf = fopen("test.txt", "rb");
	//读取文件
	fread(&s, sizeof(struct S), 1, pf);
	printf("%s %d %lf\n", s.name, s.age, s.score);
	return 0;
}

int main()
{
	FILE* pFile;
	pFile = fopen("example.txt", "wb");
	fputs("This is an apple.", pFile);
	fseek(pFile, 9, SEEK_SET);
	fputs(" sam", pFile);
	fclose(pFile);
	return 0;
}

int main()
{
	FILE* pFile;
	pFile = fopen("example.txt", "wb");
	int num = ftell(pFile);
	printf("%d ", num);
	return 0;
}

int main()
{
	FILE* pf = fopen("test.txt", "w");
	for (int i = 0; i < 10; i++) {
		fputc('a' + i, pf);
	}
	int num = ftell(pf);
	printf("%d \n", num);
	rewind(pf);
	printf("%d \n", ftell(pf));
	fclose(pf);
	pf = NULL;
	return 0;
}

int main()
{
int a = 10000;
FILE* pf = fopen("test.txt", "wb");
fwrite(&a, 4, 1, pf);//二进制的形式写到文件中
fclose(pf);
pf = NULL;
return 0;
}

//文本文件
int main(void)
{
  int c; // 注意：int，非char，要求处理EOF
  FILE* fp = fopen("test.txt", "r");
  if(!fp) {
    perror("File opening failed");
    return EXIT_FAILURE;
 }
//fgetc 当读取失败的时候或者遇到文件结束的时候，都会返回EOF
  while ((c = fgetc(fp)) != EOF) // 标准C I/O读取文件循环
 {
   putchar(c);
 }//判断是什么原因结束的
  if (ferror(fp))
    puts("I/O error when reading");
  else if (feof(fp))
    puts("End of file reached successfully");
  fclose(fp);
}