strcpy崩溃程序

Question

我创建了一个程序来导入日期和时间条目(例如。29/11/2021-15:33:56)，并将它们存储在数组中。然后，我们被要求创建一个函数(timeStampToSeconds)来将它们转换为长ints。一旦我们有了长的ints，我们就必须将条目作为秒进行比较，并使用选择排序将这些条目从最早的放到最新的。

我已经创建了下面的程序来完成这个任务，但是当我到达strcpy函数时，程序就会崩溃。

我看不出我是如何不正确地使用这个，但肯定是遗漏了什么。如果有人对如何使用它来交换我对应的char数组条目有任何建议，我们将不胜感激。为此，我可能需要使用一个完全不同的功能。

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

long int timeStampToSeconds(char array[]);

int main(void) {
    char array[50][20];
    long int intarray[50];

    char input[12], filename[] = "Timestamps", outputfile[40], file_ext[] = ".dat", temp[20];
    int i = 0, n = 0, j, x = 0, y = 0, o = 0, f = 1, result = 1;
    double datetime = 0;

    while (result != 0) {
        printf("\nPlease enter the names of the required Input file: \n");
        scanf("%10s", input);

        /* compare input & filename */
        result = strcmp(input, filename);
        
        if (result == 0) {
            printf("Input accepted!\n");
        } else
            printf("File name not found.Please try again!\n");
    }

    printf("Please enter the name of the sorted Output file to be created: \n");
    scanf("%s", &outputfile);
    strncat(&outputfile, &file_ext, 4);  /* appends file extension characters to outputfile variable characters */

    FILE *Ptr = NULL;
    FILE *cfPtr = (char *)malloc(100 * sizeof(char));

    if ((cfPtr = fopen("Timestamps.dat", "r")) == NULL) {
        printf("File could not be opened\n");
    }

    while (!feof(cfPtr)) {
        for (i = 0; i < 50; ++i) {
            for (j = 0; j < 20; ++j) {
                array[x][j] = fgetc(cfPtr);
                y++;
            }
            x++;
        }
    }

    fclose(cfPtr);

    for (int p = 0; p < 50; p++) { // loop to control number of passes
        int l;
        for (l = 0; l < 50; ++l, ++f) {   /* loop to control number of comparisons per pass */
            n = timeStampToSeconds(array[l]); /*convert to long int to compare 2 strings*/
            o = timeStampToSeconds(array[f]);

            if(n > o) {
                strcpy(temp, array[f]); /* selection sort algorithm */
                strcpy(array[f], array[l]);
                strcpy(array[l], temp);
            }
        }
    }

    if ((Ptr = fopen(outputfile, "w+")) == NULL) {
        printf("File could not be opened\n");
    }

    for (int l = 0; l < 50; ++l) {
        fprintf(Ptr, "%ld\n", intarray[l]);
    }
    fclose(Ptr);

    return 0;
}

long int timeStampToSeconds(char array[]) {
    
    long int day, mon, yr, hr, min, sec;
    long int totaldays, totalmonths, total;
    
    day = atol(array);
    mon = atol(array + 3);
    yr = atol(array + 6);
    hr = atol(array + 11);
    min = atol(array + 14);
    sec = atol(array + 17);

    hr = hr * (60 * 60); /*converts hours to seconds*/
    min = min * 60;

    day = day * 86400;
    mon = mon * 2628000;
    yr = (yr - 2000) * 31557600; /* total seconds elapsed in yrs from 2020 */

    totaldays = hr + min + sec; /* total seconds from hr/min/sec */
    totalmonths = day + mon + yr; /* total seconds from dd/mm/yy */

    total = totaldays + totalmonths;

    return total;
}

Answer 1

您将20个字节读入数组array[x]，但没有在末尾设置一个空终止符，因此它们不是正确的C字符串，strcpy可能会将超过20个字节复制到tmp中，调用未定义的行为。

还有其他问题：

读取循环使用incorrectly.

• the timeStampToSeconds函数，不处理实际月长和闰年。

以下是修改后的版本：

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

long int timeStampToSeconds(const char array[]);

int main(void) {
    char array[50][21];
    long int intarray[50];
    char input[12];
    char filename[] = "Timestamps";
    char outputfile[40];
    char file_ext[] = ".dat";
    char temp[20];
    int i = 0, n = 0, j, x = 0, y = 0, o = 0, f = 1, result = 1;
    double datetime = 0;

    while (result != 0) {
        printf("\nPlease enter the name of the required Input file: \n");
        if (scanf("%11s", input) != 1)
            return 1;

        /* compare input & filename */
        result = strcmp(input, filename);
        
        if (result == 0) {
            printf("Input accepted!\n");
        } else {
            printf("File name not found.Please try again!\n");
        }
    }

    printf("Please enter the name of the sorted Output file to be created: \n");
    scanf("%15s", &outputfile);
    strcat(outputfile, file_ext);  /* append file extension */

    FILE *Ptr;
    FILE *cfPtr;

    if ((cfPtr = fopen("Timestamps.dat", "r")) == NULL) {
        printf("File could not be opened\n");
        return 1;
    }

    for (x = 0; x < 50; x++) {
        if (fread(array[x], 1, 20, cfPtr) != 20)
            break;
        array[x][20] = '\0'
    }
    fclose(cfPtr);

    for (int p = 0; p < x; p++) { // loop to control number of passes
        int l;
        for (l = 0; l < x; ++l, ++f) {   /* loop to control number of comparisons per pass */
            n = timeStampToSeconds(array[l]); /*convert to long int to compare 2 strings*/
            o = timeStampToSeconds(array[f]);

            if (n > o) {
                strcpy(temp, array[f]); /* selection sort algorithm */
                strcpy(array[f], array[l]);
                strcpy(array[l], temp);
            }
        }
    }

    if ((Ptr = fopen(outputfile, "w+")) == NULL) {
        printf("File could not be opened\n");
        return 1;
    }

    for (int l = 0; l < x; ++l) {
        fprintf(Ptr, "%ld: %s", timeStampToSeconds(array[l]), array[l]);
    }
    fclose(Ptr);

    return 0;
}

long int timeStampToSeconds(const char array[]) {
    static const int mdays[12] = {
        31,
        31+28,
        31+28+31,
        31+28+31+30,
        31+28+31+30+31,
        31+28+31+30+31+30,
        31+28+31+30+31+30+31,
        31+28+31+30+31+30+31+31,
        31+28+31+30+31+30+31+31+31,
        31+28+31+30+31+30+31+31+31+30,
        31+28+31+30+31+30+31+31+31+30+31,
        31+28+31+30+31+30+31+31+31+30+31+30,
    };
    int day, mon, yr, hr, min, sec;
    
    /* parse 29/11/2021-15:33:56 format */
    if (sscanf("%d/%d/%d-%d:%d:%d", &day, &mon, &yr, &hr, &min, &sec) != 6) {
        /* invalid format */
        return -1;
    }

    /* compute the number of seconds since midnight */    
    sec += min * 60 + hr * 3600;

    /* compute the number of days since Jan 1st, 2000 */
    day += (yr - 2000) / 4 * (366 + 365 + 365 + 365);
    yr %= 4;
    day += yr * 365;
    if (yr > 0 || mon > 2)
        day += 1;
    day += mdays[mon - 1];
​   return sec + day * 86400L;
}