c - 读/写 txt 字符串

Question

我正在尝试学习如何在 C 中操作 txt 文件。该程序应读取 population.txt ( http://pastebin.com/Q5fNRuJG )，找到最高人口并显示它，制作一个人口大于 100 万的文件，制作一个包含所有爱尔兰城市的文件，并打印总人口。它只创建空文件，并打印总人口(现在还打印人口最多的城市)。谁能帮忙？

程序(Borland编译):

//Program that filters and processes data with fscanf()
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

main()
{
    FILE *fp;
    FILE *ireland;
    FILE *mmplus;
    int pop;
    int highest_pop=0;
    char country[50];
    char city[50];
    int total_pop=0;

    fp = fopen("population.txt","r");
    ireland = fopen("ireland_pop.txt","w");
    mmplus = fopen("greater_than_1MM.txt","w");

    //Checking if the file opened correctly
    if (fp==NULL)
    {
        printf("Cannot open file.\n");
        exit(1);
    }//End if

    //Scanning fp row by row
    while (fscanf(fp, "%s" "%s" "%i", country, city , &pop) != EOF)
    {
        //Getting the total population
        total_pop=total_pop+pop;

        //Storing the highest pop
        if (pop > highest_pop)
        {
            highest_pop=pop;
        }//End if

        //Finding 1 million+ cities
        if(pop>=1000000)
        {
            fprintf(mmplus,"%s %s %d\n",country,city,pop);
        }//End if

        //If the city is in Ireland
        if (strcmp("ireland",country) == 0)
        {
            fprintf(ireland,"%s %s %d\n",country,city,pop);
        }//End if
    }//End while

    rewind(fp); //Fix 1

    while (fscanf(fp, "%s" "%s" "%d", country, city , &pop) != EOF)
    {
        //Finding the city with the highest population
        if (pop == highest_pop)
        {
            printf("The city with the highest population is %s, %s, with a population of %d",city, country, pop);
        }//End if
    }//end while

    printf("The total population of all the cities is %d.",total_pop);
    getchar();
    fclose(fp);
    fclose(ireland);
    fclose(mmplus);
}

Answer 1

我第一次运行你的程序时得到的是空文件。第二次运行它时，我得到了正确的输出。第三次我得到一个正确的文件和一个错误的文件。

我认为我可能输入了ctrl-C 来结束程序。因此，我对程序的最后几行做了一些更改——将 newline 添加到输出中，并在等待输入之前关闭文件。之后，它每次都有效，但我无法解释所有内容。

fclose(fp);
fclose(ireland);
fclose(mmplus);
printf("The total population of all the cities is %d.\n",total_pop);
getchar();
return 0;