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 <p><span >Open <span >函数</span></span></p> <p><span > <img src="https://img-blog.csdn.net/" alt="" /></span></p> <p><span >返回值&＃xff1a;若成功&＃xff0c;返回未见描述符&＃xff1b;若出错&＃xff0c;返回<span >-1</span></span></p> <p><span > </span></p> <p><span >Path<span >参数是要打开或创建文件的名字。</span><span >Oflag</span><span >参数可用来说明此函数的多个选项。</span></span></p> <p><span >下列一个或多个常量进行<span >“</span><span >或</span><span >”</span><span >运算构成</span><span >oflag</span><span >参数&＃xff08;这些参数在头文件</span><span ><fcntl.h></span><span >中定义&＃xff09;</span></span></p> <p><span >必选项&＃xff1a;</span></p> <p><span >O_RDONLY 只读打开</span></p> <p><span >O_WRONLY 只写打开</span></p> <p><span >O_RDWR 读写打开</span></p> <p><span >大多数情况下&＃xff0c;将它们依次定义为<span >0,1,2</span></span></p> <p><span >可选项&＃xff1a;</span></p> <p><span >O_APPEND 每次写时都追加到文件的末端。</span></p> <p><span >O_CREAT 若此文件不存在则创建它。</span></p> <p><span >O_EXCL 若同时指定了<span >O_CREAT</span><span >&＃xff0c;而文件已存在&＃xff0c;则出错。</span></span></p> <p><span >O_TRUNC 如果此文件存在&＃xff0c;而且只写或读写存在&＃xff0c;则将其长度截断为<span >0</span><span >。</span></span></p> <p><span > </span></p> <p><span >Read<span >函数</span></span></p> <p><span > <img src="https://img-blog.csdn.net/" alt="" /></span></p> <p><span >返回值&＃xff1a;读到的字节数&＃xff0c;若已经到文件尾&＃xff0c;返回<span >0</span><span >&＃xff1b;若出错&＃xff0c;返回</span><span >-1</span></span></p> <p><span >将<span >fd</span><span >所指的文件传送</span><span >count</span><span >个字节到</span><span >buf</span><span >指针所指的内存中。若</span><span >count&＃61;0</span><span >&＃xff0c;则</span><span >read</span><span >不会有作业并返回</span><span >0</span><span >。</span></span></p> <p><span > </span></p> <p><span >Write<span >函数</span></span></p> <p><span > <img src="https://img-blog.csdn.net/" alt="" /></span></p> <p><span >返回值&＃xff1a;若成功&＃xff0c;返回已写的字节数&＃xff1b;若出错&＃xff0c;返回<span >-1</span></span></p> <p><span >将参数<span >buf</span><span >所指的内存中</span><span >count</span><span >个字节写入到参数</span><span >fd</span><span >所指的文件内。</span></span></p> <p><span > </span></p> <p><span >Lseek<span >函数</span></span></p> <p><span > <img src="https://img-blog.csdn.net/" alt="" /></span></p> <p><span >返回值&＃xff1a;若成功&＃xff0c;返回新的文件偏移量&＃xff1b;若出错&＃xff0c;返回为<span >-1</span></span></p> <p><span >对于参数<span >offset</span><span >的解释与</span><span >whence</span><span >的值有关。</span></span></p> <p><span >1. 若<span >whence</span><span >为</span><span >SEEK_SET</span><span >&＃xff0c;则将该文件的偏移量设置为距文件开始处</span><span >offset</span><span >个字节。</span></span></p> <p><span >2. 若<span >whence</span><span >为</span><span >SEEK_CUR</span><span >&＃xff0c;则将该文件的偏移量设置为其当前值加上</span><span >offset</span><span >&＃xff0c;其可正可负。</span></span></p> <p><span >3. 若<span >whence</span><span >为</span><span >SEEK_END</span><span >&＃xff0c;则将该文件的偏移量设置为文件长度加上</span><span >offset</span><span >&＃xff0c;其可正可负。</span></span></p> <p><span > </span></p> <p><span >例如&＃xff1a;</span></p> <p><span >Lseek(int fd, 0, SEEK_SET);//<span >定位到文件头</span></span></p> <p><span >Lseek(int fd, 0, SEEK_END);//<span >定位到文件尾</span></span></p> <p><span >Lseek(int fd, 0, SEEK_CUR);//<span >定位到文件当前位置</span></span></p> <p><span ></span></p><p></pre><br><span ></span><p></p> <p>Int main(int argc,char argv);</p> <p>其中<span >argc</span><span >为运行命令行中输入参数的个数</span></p> <p>Argv<span >字符数组中的每个元素代表每个参数</span></p> <p> <img src="https://img-blog.csdn.net/" alt="" /></p> <p> </p> <br><br /> <br><br /> <br>