文件的打开与关闭

文件的打开

FILE *fopen(const char *fname,const char *mode);

模式字符串	功能
“r”	以只读模式打开文本文件
“w”	以只写模式打开文本文件
“a”	以追加模式打开文本文件
“r+”	以读写模式打开文本文件
“w+”	以读写模式打开文本文件
“a+”	以读写模式打开文本文件
“rb”	以只读模式打开二进制文件
“wb”	以只写模式打开二进制文件
“ab”	以追加模式打开二进制文件
“rb+”	以读写模式打开二进制文件
“wb+”	以读写模式打开二进制文件
“ab+”	以读写模式打开二进制文件

FILE *pfile = fopen("D:\\test.txt","r");
if(pfile != NULL)
	printf("File opened successfully.\n");
else
	printf("Failed to open file.\n");

File opened successfully.

Failed to open file.

FILE *pfile = fopen("D:\\test.txt","w");

FILE *pfile = fopen("D:\\test.txt","a");

文件的关闭

int fclose(FILE *stream);

FILE *pfile = fopen("D:\\test.txt","r");
if(pfile)
{
	printf("File opened successfully.\n");
	if(!fclose(pfile))
		printf("File closed successfully.\n");
	else
		printf("File closure failed successfully.\n");
}
else
	printf("Failed to open file.\n");

File opened successfully.
File closed successfully.

Failed to open file.

标准文件流

文件流的重定向

FILE *freopen(const char *fname,const char *mode,FILE *stream);

freopen("D:\\test.txt","w",stdout);
printf("Hello");
putchar(' ');
printf("World");

Hello World

char ch1,ch2;
char str[100];
freopen("D:\\test.txt","r",stdin);
scanf("%c",&ch1);
ch2 = getchar();
gets(str);
printf("ch1:%c\nch2:%c\nstr:%s\n",ch1,ch2,str);

ch1:H
ch2:e
str:llo World

文件的读写

以字符的方式读写文件

int fputc(int ch,FILE *stream);

#include <stdio.h>
int main()
{
	char str[] = "Red apple";
	FILE *pfile = fopen("D:\\test.txt","w");
	if(pfile)
	{
		char *ptmp = str;
		while(*ptmp)
		{
			fputc(*ptmp,pfile);
			++ptmp;
		}
		fclose(pfile);
		puts("Write to complete.");
	}
	else
		puts("File opening failed.");
	return 0;
}

int fflush(FILE *stream);

if(pfile)
	{
		char *ptmp = str;
		while(*ptmp)
		{
			fputc(*ptmp,pfile);
			++ptmp;
		}
		fflush(pfile);			//刷新输出缓冲区
		fclose(pfile);			//关闭文件
		puts("Write to complete.");
	}

int fgetc(FILE *stream);

#include <stdio.h>
int main()
{
	char buf[128];
	FILE *pfile = fopen("D:\\test.txt","r");
	if(pfile)
	{
		char *p = buf;
		while((*p = fgetc(pfile)) != EOF)
			++p;
		*p = '\0';
		fclose(pfile);
		printf("The read content is: %s\n",buf);
	}
	else
		puts("File opening failed.");
	return 0;
}

The read content is: Red apple

以行的方式读写文件

int fputs(const char *str,FILE *stream);

#include <stdio.h>
int main()
{
	FILE *pfile = fopen("D:\\test.txt","w");
	if(pfile)
	{
		if(fputs("Red appple",pfile) != EOF)
			printf("File written successful.\n");
		else
			printf(Failed to write file.\n);
		fclose(pfile);
	}
	else
		printf("File opening failed.\n");
	return 0;
}

File written successful.

char *fgets(char *str,int num,FILE *stream);

#include <stdio.h>
int main()
{
	char buf[128];
	FILE *pfile = fopen("D:\\test.txt","r");
	if(pfile)
	{
		if(fgets(buf,128,pfile))
			printf("The read content is: %s\n",buf);
		else
			printf("Failed to read file.\n");
		fclose(pfile);
	}
	else
		printf("File opening failed.\n");
	return 0;
}

The read content is: Red apple

以格式化的方式读写文件

int fprintf(FILE *stream,const char *format,...);

struct STU
{
	int num;
	char name[20];
	float score;
};

int main()
{
	struct STU stu = {100,"zhangsan",90.5};
	FILE *pfile = fopen("D:\\test.txt","w");
	if(pfile)
	{
		fprintf(pfile,"%d %s %.2f",stu.num,stu.name,stu.score);
		fclose(pfile);
	}
	else
		printf("File opening failed.\n");
	return 0;
}

100 zhangsan 90.50

int sprintf(char *buffer,const char *format,...)

int main()
{
	struct STU stu = {100,"zhangsan",90.5};
	char buf[1024];
	sprintf(buf,"%d %s %.2f",stu.num,stu.name,stu.score);
	puts(buf);
	return 0;
}

100 zhangsan 90.50

int fscanf(FILE *stream,const char *format,...);

int main()
{
	struct STU stu;
	FILE *pfile = fopen("D:\\test.txt","r");
	if(pfile)
	{
		fscanf(pfile,"%d%s%f",&stu.num,stu.name,&stu.score);
		fclose(pfile);
		printf("num:%d\nname:%s\nscore:%.2f\n",stu.num,stu.name,stu.score);
	}
	else
		printf("File opening failed.\n");
	return 0;
}

num:100
name:zhangsan
score:90.50

以块的方式读写文件

int fwrite(const void *buffer,size_t size,size_t count,FILE *stream);

#include <stdio.h>
struct STU
{
	int num;
	char name[20];
	float score;
};
int main()
{
	struct STU stu = {100,"zhangsan",90.5};
	FILE *pfile = fopen("D:\\test.dat","wb");
	if(pfile)
	{
		fwrite(&stu,sizeof(stu),1,pfile);
		fclose(pfile);
	}
	else
		printf("File opening failed.\n");
	return 0;
}

int fread(void *buffer,size_t size,size_t num,FILE *stream);

#include <stdio.h>
struct STU
{
	int num;
	char name[20];
	float score;
};
int main()
{
	struct STU stu;
	FILE *pfile = fopen("D:\\test.dat","rb");
	if(pfile)
	{
		fread(&stu,sizeof(stu),1,pfile);
		fclose(pfile);
		printf("num:%d\nname:%s\nscore:%.2f\n",stu.num,stu.name,stu.score);
	}
	else
		printf("File opening failed.\n");
	return 0;
}