以下兩個代碼均在Linux下GCC測試通過
要求：
字符串長度為16
字符串只能包含大小寫字母和數字
要求生成20000000行的TXT文本
/**********************************
* Author: Ervin_Zhao(2012.6)
* Compile: gcc
* Create a file named test.txt, included 2000w line random string
* string have 16 num used A-Z, a-z, 0-9
*/
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
int main(void)
{
char array[]="QWERTYUIOPASDFGHJKLZXCVBNMqwertyuiopasdfghjklzxcvbnm1234567890";
char buff[170000];
char *buff2 = buff;
int file = open("test.txt", O_WRONLY|O_CREAT, S_IRWXU|S_IRGRP|S_IROTH);
int i;
int temp[4];
char *p = (char *)temp;
for(i = 0; i<20000000; i++)
{
temp[0] = rand();
temp[1] = rand();
temp[2] = rand();
temp[3] = rand();
buff2[0] = array[p[0]%(sizeof(array)-1)];
buff2[1] = array[p[1]%(sizeof(array)-1)];
buff2[2] = array[p[2]%(sizeof(array)-1)];
buff2[3] = array[p[3]%(sizeof(array)-1)];
buff2[4] = array[p[4]%(sizeof(array)-1)];
buff2[5] = array[p[5]%(sizeof(array)-1)];
buff2[6] = array[p[6]%(sizeof(array)-1)];
buff2[7] = array[p[7]%(sizeof(array)-1)];
buff2[8] = array[p[8]%(sizeof(array)-1)];
buff2[9] = array[p[9]%(sizeof(array)-1)];
buff2[10] = array[p[10]%(sizeof(array)-1)];
buff2[11] = array[p[11]%(sizeof(array)-1)];
buff2[12] = array[p[12]%(sizeof(array)-1)];
buff2[13] = array[p[13]%(sizeof(array)-1)];
buff2[14] = array[p[14]%(sizeof(array)-1)];
buff2[15] = array[p[15]%(sizeof(array)-1)];
buff2[16] = '\n';
buff2 += 17;
if(buff2 >= (buff+sizeof(buff)))
{
write(file, buff, sizeof(buff));
buff2 = buff;
}
}
close(file);
return 0;
}
程序執行時間：
real 0m11.494s
user 0m7.860s
sys 0m0.296s
