文件I/O与标准I/O

约定不等于承诺〃 2022-06-10 07:40 155阅读 0赞

# **返回值汇总：** #

![这里写图片描述][SouthEast]

## **printf的四种输出方式** ★ ##

1、遇到 \\n 2、遇到scanf() 3、fflush(stdout) 4、缓冲区满

## **函数feof（）** ##

feof（）函数可以检查到文件读写位置标记是否移到文件末尾，一句话概括就是判断文件有没有读完。读完了feof（fp）返回值为1，否则为0。

## **用文件I/O编写拷贝文件程序** ##

**代码：**

/*****************************************************
         File name:file_copy.c
    
     Author: Tang Zhiqian
    
      Date:2017-08-11 19:50
    *****************************************************/
    
    #include <stdio.h>
    #include <sys/types.h>
    #include <sys/stat.h>
    #include <fcntl.h>
    
    int main(int argv,char **argc)    //命令行参数
    {
        printf("%s\n",argc[0]);
        printf("%s\n",argc[1]);
        printf("%s\n",argc[2]);
    
        if (argv != 3)    //判断输入是否合法
        {
            printf("please input the right command: ./a.out filename1 filename2\n");
            return 1;
        }
        int fd1 = open(argc[1],O_RDONLY);    //打开文件1，只读方式打开
        if (-1 == fd1)
        {
            perror("open file1");
            return 2;
        }
    
        int fd2 = open(argc[2],O_WRONLY | O_CREAT | O_APPEND);    打开文件2
        if (-1 == fd2)
        {
            perror("open file2");
            close(fd1);
            return 3;
        }
    
        char buffer[1024];    //定义缓冲区
        int count1 = 1;
        while(count1)
        {
            count1 = read(fd1,buffer,1024);    //返回值为实际读取的字节数
            if (-1 == count1)
            {
                perror("read");
                close(fd1);
                close(fd2);
                return 4;
            }
            int count2 = write(fd2,buffer,count1);    //写入文件2
            if (-1 == count2)
            {
                perror("write");
                close(fd1);
                close(fd2);
                return 5;
            }
        }
        close(fd1);
        close(fd2);
    
        return 0;
    }

可以拷贝任何文件。

## **用标准I/O写拷贝文件程序** ##

/***************************************************** File name:copy_file.c Author: Tang Zhiqian Date:2017-08-13 09:34 *****************************************************/
    
    #include <stdio.h>
    
    #define MAX 1024
    
    int main(int argc,char **argv)
    {
        if (3 != agrc)
        {
            printf("input:./a.out filename1 filename2\n");
            return;
        }
        int fd1 = open(argv[1],O_RDONLY);
        if (-1 == fd1)
        {
            perror("open file1");
            return 1;
        }
    
        int fd2 = open(argv[2],O_RDWR | O_CREAT | O_APPEND);
        if (-1 == fd2)
        {
            perror("open file2");
            close(fd1);
            return 2;
        }
        char buffer[MAX];
        int count1 = 1
        while(count1)
        {
            count1 = read(fd1,buffer,MAX);
            if (-1 == count1)
            {
                perror("read");
                close(fd1);
                close(fd2);         
                return 3;
            }
    
            int count2 = write(fd2,buffer,count1);
            if (-1 == count2)
            {
                perror("write");
                close(fd1);
                close(fd2);
                return 4;
            }
            menset(buffer,0,MAX);
        }
    
        return 0;
    }

跟文件I/O几乎一样。

[SouthEast]: /images/20220610/c63512db92b54e898b31cf8d5bac933c.png