生成一组id供测试用

/* id的格式为usr+数字，生成文件中每个id占一行 */

#include <iostream>
#include <string>
#include <sstream>
#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>

 

using namespace std;

 

int main(int argc, char *argv[])
{   
    if (argc != 3)
    {
        cout << "usage: gen [count] [outfile]" << endl;
        exit(EXIT_FAILURE);
    }

 

    int nCount = atoi(argv[1]);
    string strOutFile(argv[2]);
   
    int nFd = open(strOutFile.c_str(), O_WRONLY | O_CREAT | O_EXCL, S_IRWXU);
   
    if (nFd < 0)
    {
        cout << "open failed: " << strerror(errno) << endl;
        exit(EXIT_FAILURE);
    }

 

    string strPrefix("usr");
    stringstream id;

 

    for (int i = 1; i <= nCount; i++)
    {
        id.str("");
        id << i << endl;

 

        string strUsr = strPrefix + id.str();
        size_t nBytes = strlen(strUsr.c_str());

 

        if (write(nFd, strUsr.c_str(), nBytes) != (ssize_t)nBytes)
        {
            cout << "write failed: " << strerror(errno) << endl;
            close(nFd);
            exit(EXIT_FAILURE);
        }
    }

 

    close(nFd);
    exit(EXIT_SUCCESS);
}

 

//g++ gen.cpp -Wall -g -O -o gen
//./gen 1000000 1.txt