io进程day2

拷贝文件

#include<myhead.h>

#define MAXSIZE 1024

int main(int argc, const char *argv[])
{
	//定义文件和缓存数组
	int fdin,fdout;
	char buff[MAXSIZE]={0};
	ssize_t read_size=0;//承接read了几个字节

	//打开两个文件
	fdin=open(argv[1],O_RDONLY);
	if(fdin==-1)
	{
		ERR_MSG("file_in open error");
	}

	fdout=open(argv[2],O_WRONLY|O_CREAT|O_TRUNC,0664);
	if(fdout==-1)
	{
		close(fdout);
		ERR_MSG("file_out open error");
	}

	//循环读取，判断写入的个数是否等于读取的个数
	while((read_size=read(fdin,buff,MAXSIZE))>0)
	{
		if((write(fdout,buff,read_size))!=read_size)
		{
			printf("copy error! ");
			close(fdin);
			close(fdout);

			return -1;
		}

	}
	//检查读取是否错误
	if(read_size==-1)
	{
		ERR_MSG("read last error");
		close(fdin);
		close(fdout);
	}
	
	//关闭
	if(close(fdin)==-1)
		ERR_MSG("close file_in error");
	if(close(fdout)==-1)
		ERR_MSG("close file_out error");
	printf("拷贝成功");
}

	return 0;
}

拷贝照片

#include<myhead.h>

#define MAX 4096

int main(int argc, const char *argv[])
{
	FILE *src;
	FILE *dest;
	size_t read_size=0;
	unsigned char buff[MAX]={0};
	src=fopen(argv[1],"rb");
	dest=fopen(argv[2],"wb");
	if(src==NULL)
	{		
		ERR_MSG("src open error");
	}
	if(dest==NULL)
	{		
		ERR_MSG("dest open error");
		fclose(dest);
	}
	
	while((read_size=fread(buff,1,MAX,src))>0)
	{
		if(fwrite(buff,1,read_size,dest)!=read_size)
			ERR_MSG("write error!");

	}

	if(ferror(src))
		ERR_MSG("read error!");

	if(fclose(src)!=0)
		ERR_MSG("src close error");
	if(fclose(dest)!=0)
		ERR_MSG("dest close error");

	printf("photo copy success");
			
	return 0;
}

计算文件大小

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>

// 错误处理宏
#define ERR_MSG(msg) do { \
    perror(msg); \
    exit(EXIT_FAILURE); \
} while(0)


// 方法2：通过移动文件指针获取文件大小
off_t get_file_size_by_lseek(const char *filename) 
{
    int fd = open(filename, O_RDONLY);
    if (fd == -1) 
	{
        ERR_MSG("open failed");
    }
    
    // 将文件指针移到末尾，返回当前位置（即文件大小）
    off_t size = lseek(fd, 0, SEEK_END);
    if (size == -1) {
        close(fd);
        ERR_MSG("lseek failed");
    }
    
    close(fd);
    return size;
}

int main(int argc, char *argv[]) 
{
   
    off_t size2 = get_file_size_by_lseek(argv[1]);
    // 输出结果
    printf("文件: %s\n", argv[1]);
    printf("通过lseek获取的大小: %ld 字节\n", (long)size2);

    return 0;
}