了解I/O系统调用的特点并通过性能测试对此有直观的认识



1、先根据题目生成所需的4kb，256kb，64mb的txt文件

2、根据main函数的int main (int argc, char *argv[])参数特性，可以设计成 ：

if (4 != argc)

{

printf ("输入格式错误!\n")

exit(0)

}

来确定输入参数是4个

/*----------------------------------------------------------------

@argc[0] ./你的程序名



@argc[1] 用于测试的文件名



@argv[2] 选择的操作方式 fopen、open或者mmap的方式

"1":标准 C的I/O库函数 fopen fread fwrite

"2":Unix的I/O函数 open read write

"3":open和mmap



@argv[3] read/fread读取的字节数大小

-----------------------------------------------------------------*/

最后根据相应的功能实现相应的操作

-Understand the characteristics of I/O system calls, and this performance test has an intuitive understanding of a first generation required under the subject 4kb, the 256kb, 64 MB of txt file, according to the main function of an int main (int argc, char* argv []) parameters characteristic can be designed to: if (4 = argc) {printf (" input format error! \ n" )　exit (0) } to determine the input parameters is 4 /*---------------------------------------------------------------- @ argc [0]./your program @ argc [1] is used to test the file name @ argv [2] selected mode of operation of the fopen, open or mmap mode " 1"　: the standard C, I/O library functions the fopen fread the fwrite " 2" : Unix I/O function open the read the write " 3" : the open and the mmap @ in argv [3] read/fread to read the size of the number of bytes-----------------------------------------------------------------*/and finally the appropriate action according to the function