C语言全面细致讲解文件操作

#include <stdio.h>
int main()
{
	FILE* pf = fopen("test.txt", "w");//打开文件，以写的方式打开，文件名叫"test,txt"
	if (pf == NULL)
	{
		perror("fopen");
		return 1;
	}
	//文件操作
	//关闭文件
	fclose(pf);
	pf = NULL;
	return 0;
}

#include <stdio.h>
int main()
{
	FILE* pf = fopen("test.txt", "w");//打开文件名，以写的方式打开
	if (pf == NULL)
	{
		perror("fopen");
		return 1;
	}
	写文件
	fputc('a', pf);//往文件里输出
	fputc('b', pf);
	fputc('c', pf);
//文件在被操作过程的时候其实是有一个位置信息的，在操作过程中时刻发生变化
	关闭文件
		fclose(pf);
	pf = NULL;
	return 0;
}

#include <stdio.h>
int main()
{
	FILE* pf = fopen("test.txt", "r");//打开文件名，以读的方式打开
	if (pf == NULL)
	{
		perror("fopen");
		return 1;
	}
	//读文件
	char ch=fgetc(pf);//这是我们不知道读到了什么可以打出来看看
	printf("%c\n", ch);
	 ch = fgetc(pf);
	printf("%c\n", ch);
	ch = fgetc(pf);
	printf("%c\n", ch);
	//关闭文件
	fclose(pf);
	pf = NULL;
	return 0;
}

#include <stdio.h>
int main()
{
	FILE* pfRead = fopen("test1.txt", "r");
	if (pfRead == NULL)
	{
		perror("open file for reading");
		return 1;
	}
	FILE* pfWrite = fopen("test2.txt", "w");
	if (pfWrite == NULL)
	{
		perror("open file for reading");
		fclose(pfRead);
		pfRead = NULL;
		return 1;
	}
	char ch = 0;
	while((ch = fgetc(pfRead)) != EOF)
	{
		fputc(ch, pfWrite);
	}
	//关闭文件
	fclose(pfRead);
	pfRead = NULL;
	fclose(pfWrite);
	pfWrite = NULL;
	return 0;
}

#include <stdio.h>
int main()
{
	FILE* pf = fopen("test.txt", "w");//打开文件名，以写的方式打开
	if (pf == NULL)
	{
		perror("fopen");
		return 1;
	}
	//写数据
	fputs("hello world\n",pf);\\不会自动换行，所以自己可以加上换行符
	fputs("haha\n", pf);
	fclose(pf);
	pf = NULL;
	return 0;
}

#include <stdio.h>
int main()
{
	char input [20]= { 0 };//将读到的数据存放进来
	FILE* pf = fopen("test.txt", "r");//打开文件名，以写的方式打开
	if (pf == NULL)
	{
		perror("fopen");
		return 1;
	}
	//读数据
	fgets(input, 20, pf);
	printf("%s", input);
	fgets(input, 20, pf);
	printf("%s", input);
	fclose(pf);
	pf = NULL;
	return 0;
}

#include <stdio.h>
struct stu
{
	char name[20];
	int age;
	float score;
};
int main()
{
	struct stu s = { "zhangsan",20,66.5f };
	FILE* pf = fopen("test.txt", "w");
	if (pf == NULL)
	{
		perror("fopen");//如果打开失败，打印失败原因
		return 1;
	}
	fprintf(pf, " %s %d %f", s.name, s.age, s.score);
	fclose(pf);
	pf = NULL;
	return 0;
}

#include <stdio.h>
struct stu
{
	char name[20];
	int age;
	float score;
};
int main()
{
	struct stu s = { 0 };
	FILE* pf = fopen("test.txt", "r");
	if (pf == NULL)
	{
		perror("fopen");
		return 1;
	}
	fscanf(pf, "%s %d %f", s.name,&( s.age), &(s.score));
	printf("%s %d %f", s.name, s.age, s.score);
	fclose(pf);
	pf = NULL;
	return 0;
}

#include <stdio.h>
struct stu
{
	char name[20];
	int age;
	float score;
};
#include <stdio.h>
int main()
{
	struct stu s = { "zhangsan",20,66.5f };
	FILE* pf = fopen("test.txt", "wb");
	if (pf == NULL)
	{
		perror("fopen file for writting");
		return 1;
	}
	fwrite(&s,sizeof(struct stu),1,pf);
	fclose(pf);
	pf = NULL;
	return 0;
}

#include <stdio.h>
struct stu
{
	char name[20];
	int age;
	float score;
};
#include <stdio.h>
int main()
{
	struct stu s = {0 };
	FILE* pf = fopen("test.txt", "rb");
	if (pf == NULL)
	{
		perror("fopen file for writting");
		return 1;
	}
	fread(&s, sizeof(struct stu), 1,pf);
	printf("%s %d %f", s.name, s.age, s.score);
	fclose(pf);
	pf = NULL;
	return 0;
}

#include <stdio.h>
int main()
{
	FILE* pf = fopen("test.txt", "w");
	if (pf == NULL)
	{
		perror("open");
		return 1;
	}
	fputs("ABCDEF", pf);
	fseek(pf,2, SEEK_SET);//从起始位置开始偏移
	//从当前位置开始偏移
	//从末尾开始偏移
	fputc('G', pf);
	fclose(pf);
	pf = NULL;
	return 0;
}

#include <stdio.h>
int main()
{
	FILE* pf = fopen("test.txt", "w");
	if (pf == NULL)
	{
		perror("open");
		return 1;
	}
	fputs("ABCDEF", pf);
	fseek(pf,2, SEEK_SET);//这时候指针指向了从起始位置开始偏移，偏移量为2的位置上的C
	int ret = ftell(pf);//因为此时指针指向C，它相当于起始位置偏移量为2
	printf("ret = %d\n", ret);
	fclose(pf);
	pf = NULL;
	return 0;
}

#include <stdio.h>
#include <stdlib.h>
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);
}

#include <stdio.h>
enum { SIZE = 5 };
int main(void) {
    double a[SIZE] = {1.,2.,3.,4.,5.};
    FILE *fp = fopen("test.bin", "wb"); // 必须用二进制模式
    fwrite(a, sizeof *a, SIZE, fp); // 写 double 的数组
    fclose(fp);
    double b[SIZE];
    fp = fopen("test.bin","rb");
    size_t ret_code = fread(b, sizeof *b, SIZE, fp); // 读 double 的数组
    if(ret_code == SIZE) 
    {
        puts("Array read successfully, contents: ");
        for(int n = 0; n < SIZE; ++n) printf("%f ", b[n]);
        putchar('\n');
   } 
   else 
   { 
   // error handling
    if (feof(fp))
     printf("Error reading test.bin: unexpected end of file\n");
       else if (ferror(fp))
        {
           perror("Error reading test.bin");
       }
   }
    fclose(fp);
}