C语言强化——文件

文件操作

• fopen与fclose
• fread与fwrite
• fseek
• fputs与fgets
• fscanf与fprintf

fopen与fclose

#include<stdio.h>

int main() {
	FILE *fp;
	char c;
	fp = fopen("1.txt", "r");
	if (NULL == fp) {
		perror("fopen");   //perror()函数打印str(字符串)和一个相应的执行定义的错误消息到全局变量errno中.
	}
	while ((c = fgetc(fp)) != EOF) {
		putchar(c);
	}
	fclose(fp);
	return 0;
}

fread与fwrite

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main()
{
	FILE *fp;
	char buf[128] = { 0 };
	int i = 0x12340a78;
	int ret;
	fp = fopen("1.txt", "rb+");
	if (NULL == fp)
	{
		perror("fopen");
	}
	//打印文件内容
	//while(memset(buf,0,sizeof(buf)),(ret=fread(buf,sizeof(char),sizeof(buf)-1,fp))>0)
	//{
	//	printf("%s",buf);
	//}

	//写入文件
	strcpy(buf, "hello\nworld");
	fwrite(buf, sizeof(char), strlen(buf), fp);

	//fwrite的返回值是写的对象的数量
	/*ret=fwrite(&i,sizeof(int),1,fp);
	i=0;*/
	/*fread(&i,sizeof(int),1,fp);
	printf("i=%x\n",i);*/
	fclose(fp);

	return 0;
}

fseek

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main()
{
	FILE *fp;
	int ret;
	char buf[128]={0};
	fp=fopen("1.txt","r+");
	if(NULL==fp)
	{
		perror("fopen");
	}
	ret=fseek(fp,6,SEEK_SET);   //成功返回0，失败返回非零
	ret=fread(buf,sizeof(char),2,fp);
	printf("buf=%s\n",buf);
	fseek(fp,0,SEEK_CUR);
	ret=fwrite("you are how",sizeof(char),11,fp);
	fclose(fp);
	return 0;
}

fputs与fgets

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main()
{
	FILE *fp;
	int ret;
	char buf[128];
	fp=fopen("1.txt","r+");
	if(NULL==fp)
	{
		perror("fopen");
	}
	while(fgets(buf,sizeof(buf),stdin))
	{
		fputs(buf,fp);   //等价于printf("%s\n",buf);
	}
	return 0;
}

fscanf与fprintf

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct{
	int num;
	char name[20];
	float score;
}Stu;
int main()
{
	int num=20;
	float score=98.5;
	Stu sArr[3]={1001,"zhangfei",66.5,1007,"liubei",96.5,1005,"guanyu",97.3};
	int ret,i;
	FILE *fp=fopen("file.txt","r+");
	if(NULL==fp)
	{
		perror("fopen");
	}
	//ret=fprintf(fp,"%d %5.2f\n",num,score);
	//num=0;
	//score=0;
	//ret=fscanf(fp,"%d%f",&num,&score);
	for(i=0;i<3;i++)
	{
		ret=fprintf(fp,"%d %s %5.2f\n",sArr[i].num,sArr[i].name,sArr[i].score);
	}
	fseek(fp,0,SEEK_SET);
	memset(sArr,0,sizeof(sArr));
	for(i=0;i<3;i++)
	{
		ret=fscanf(fp,"%d%s%f",&sArr[i].num,sArr[i].name,&sArr[i].score);
	}
	fclose(fp);
	return 0;
}