c - 逐行读取文件，它只存储文件中的最后一行

Question

我必须从如下所示的 .txt 文件中读取:

New York,4:20,3:03Kansas City,12:03,3:00North Bay,16:00,0:20Kapuskasing,10:00,4:02Thunder Bay,0:32,0:31

I am trying to separate each element into its own array is the end goal so I can use it for something else.

My while loop reads the file correctly, but is only storing the last line of the file in an array and I cant figure out the reason for this. Also file being read could be any number of lines. I am sure its reading each line, as it prints each line it reads perfectly. So I believe the issue lies in storing what it is reading.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#pragma warning(disable: 4996)

// a function to remove the trailing carriage return
void clearTrailingCarraigeReturn(char *buffer);

/* == FUNCTION PROTOTYPES == */

/* == CONSTANTS == */
#define RECORD_SIZE     256
#define NUM_RECORDS     5
#define CHUNK_SIZE  1024    
#define STRING_SIZE 80

// MAIN
int main(int argc, char *argv[]) {
    FILE    *fp;
    char    flightInfo[RECORD_SIZE] = { 0 };
    char    cityName[20] = {};
    char    flightHour[20] = {};
    char    flightMin[20] = {};
    char    layoverHour[20] = {};
    char    layoverMin[20] = {};
    int     i = 0;

    struct flightInfo {
        char flightName[20];
        double flightTime;
        double layoverTime;
    };

    fp = fopen(argv[1], "r");
    // first - we'll check the command-line arguments to ensure that the user specified 
    // a single argument - which we will assume is the name of a file
    if (argc != 2) {
        printf("Sorry - you need to specify the name of a file on the command line.\n");
        return -1;
    }

    if (fp == NULL) {
        printf("Can't open the TEXT file for reading\n");
        return -4;
    }

    // get each of the lines from the file
    while (fgets(flightInfo, sizeof flightInfo, fp) > 0) {
        clearTrailingCarraigeReturn(flightInfo);
        // display the line we got from the file
        printf("  >>> read record [%s]\n", flightInfo);
    }

    // we exited the reading loop - was it because we read the EOF?
    if (feof(fp)) {
        printf(" [DONE reading the file ... we've reached the EOF]\n");
    } else {
        // we exited the loop because of an error
        if (ferror(fp)) {
            // there's an error
            printf("Error reading a record from the file\n");
            if (fclose(fp) != 0) {
                // we can't even close the file
                printf("Can't close the TEXT file we opened for reading\n");
            }
            return -5;
        }
    }
}

// This function locates any carriage return that exists in a record
// and removes it ...
void clearTrailingCarraigeReturn(char *buffer) {
    char *whereCR = strchr(buffer, '\n');
    if (whereCR != NULL) {
        *whereCR = '\0';
    }
}

Answer 1

您的代码中存在多个问题:

• 您应该在尝试打开文件之前测试命令行参数是否存在。

• 您的读取循环测试不正确:fgets() 返回指向目标数组的指针或 NULL，因此您不应使用 > 0 而不是:

  while (fgets(flightInfo, sizeof flightInfo, fp) != 0)
  

• 字符'\n' 称为换行符，而不是回车符。在遗留平台上，\n 在文本文件 0D 0A 中被转换为 2 个字节，即:回车 和 < em>换行。

• 循环读取文件内容，但不解析行内容并将其存储到您为此定义的变量中。您应该解析该行，转换值并将信息存储到 flighInfo 结构数组中的下一个条目:

      if (sscanf(flightInfo, "%19[^,],%2[0-9]:%2[0-9],%2[0-9]:%2[0-9]",
                 cityName, flightHour, flightMin, layoverHour, layoverMin) == 5) {
          /* convert the times into `double` values and store the info */
      } else {
          /* report the error, exit */
      }
  

• struct flightInfo 标记和 char 数组使用相同的名称。这是令人困惑和容易出错的。您应该将 char 数组重命名为 line 或 buf。

• 在任何情况下您都应该关闭该文件。