Question

以下代码的行为与预期不符。

#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <stdbool.h>

struct dest
{
    char filename[20], keyword[20];
    bool opened;
    FILE * file;
};


void display_data(const struct dest p) {
    printf("Keyword: %s, Filename: %s, Used: %s\n", p.keyword, p.filename, p.opened ? "Yes" : "No");
}

int main(int argc, char const *argv[])
{
    // declaring variables
    float lon, lat;
    char info[80];
    FILE *reader;

    // checking required arguments
    if ((argc+1) % 2 || argc < 2) {
        fprintf(stderr, "Usage: %s file_to_read file_for_unknown type file type file ...\n", argv[0]);
        return 2;
    }

    // opening the reader
    if (!(reader = fopen(argv[1], "r"))) {
        fprintf(stderr, "File can't be accessed: %s\n", argv[1]);
        return 2;
    }

    // creating important globals
    const short pairs = (argc-3)/2;
    struct dest data[pairs];

    struct dest other;
    strcpy(other.filename, argv[2]);
    other.opened = false;

    // gathering data
    short times = 4;
    for(short i = 4; i < argc; i += 2) {
        data[i-times].opened = false;
        strcpy(data[i-times].keyword, argv[i-1]);
        strcpy(data[i-times].filename, argv[i]);
        times += 1;
    }

    // finally, scanning the file ..
    struct dest *use_f; // pointer for the wanted destination ..
    bool known;
    while (fscanf(reader, "%f,%f,%79[^\n]", &lat, &lon, info)) {

        // deciding which file to use ..
        known = false;
        for(short i=0; i < pairs; ++i) {
            if (strstr(info, data[i].keyword)) {
                known = true;
                use_f = &data[i];
            }
        }

        if (!(known)) {
            use_f = &other;
        }

        // checking the file ..
        if (!((*use_f).opened)) {
            (*use_f).file = fopen((*use_f).filename, "w");
            (*use_f).opened = true;
        }

        // writing to the file ..
        fprintf((*use_f).file, "%f,%f,%s\n", lat, lon, info);
    }

    // closing all data streams, and informing user ..
    for (short i=0; i < pairs; ++i) {
        display_data(data[i]);
        if (data[i].opened) {
            fclose(data[i].file);
            data[i].opened = false;
        }
    }

    fclose(reader);
    fclose(other.file);

    return 0;
}

用于运行它的命令是..

./分类spooky.csv other.csv UFO UFOS.csv＃我根本没有输出

似乎while循环实际上并没有结束，这很神秘，因为文件（spooky.csv）只有11行！

30.685163，-68.137207，类型=雪人
  28.304380，-74.575195，类型= UFO
  29.132971，-71.136475，类型=船舶
  28.343065，-62.753906，类型=埃尔维斯
  27.868217，-68.005371，类型= Goatsucker
  30.496017，-73.333740，类型=消失
  26.224447，-71.477051，类型= UFO
  29.401320，-66.027832，类型=船舶
  37.879536，-69.477539，类型=埃尔维斯
  22.705256，-68.192139，类型=埃尔维斯
  27.166695，-87.484131，类型=埃尔维斯

它只是继续写入other.file，但我不知道为什么..
程序根本没有结束，有人可以向我解释一下吗？

Answer 1

从fscanf()联机帮助页：“如果在发生任何转换（例如文件结束）之前发生输入故障，则返回值EOF。”

这是一个提示...... EOF不等于0.你的while循环永远不会终止。

该代码不打印预期的输出，为什么？

1 个答案: