c - fgets() strtok()

Question

嘿，我的任务是从一个用空格分隔的文件中读取数据并对数据进行排序。我一直有seg错误，我无法弄清楚我的代码出了什么问题。谢谢你的帮助。

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define MAX_LINE 100
#define MAX_NAME 30
int countLinesInFile(FILE* fptr);
int findPlayerByName(char **names, char* target, int size);
int findMVP(int* goals, int* assists, int size);
void printPlayers(int* goals, int* assists, char** names, int size);
void allocateMemory(int **goals, int** assists, char*** names, int size);
void sortPlayersByGoals(int* goals, int* assists, char** names, int size);
void writeToFile(FILE *fptr, int* goals, int* assists, char** names, int size);
void readLinesFromFile(FILE* fptr, int* goals, int* assists, char** names, int        numLines);
int main(int argc, char **argv)
{
    FILE *fptr;
    int size;
    int* goals;
    int* assists;
    char** names;
    if(argc != 2)
    {
            printf("Invalid number of argumentsn");
            return 1;
    }
    fptr = fopen(argv[1], "r");
    if(fptr == NULL)
    {
            printf("Failed to open input file.n");
            return 2;
    }
    size = countLinesInFile(fptr);
    allocateMemory(&goals, &assists, &names, size);
    int numLines;
    numLines = size;
    readLinesFromFile(fptr, goals, assists, names, numLines);
    printPlayers(goals, assists, names, size);
    return 3;
}
void printPlayers(int* goals, int* assists, char** names, int size)
{
    int i;
    for(i = 0; i < size; i++)
    {
    printf("%c     %d     %d", *(names + i), *(goals + i), *(assists + i));
    }
}
void readLinesFromFile(FILE* fptr, int* goals, int* assists, char** names, int numLines)
{
    char line[MAX_LINE];
    int i;
    char* value;
    for(i = 0; i < numLines; i++)
    {
            fgets(line, MAX_LINE, fptr);
            value = strtok(line, " ");
            *(*names + i) = atoi(value);
            value = strtok(line, " ");
            *(goals + i) = atoi(value);
            value = strtok(line, " ");
            *(assists + i) = atoi(value);
    }

}
void allocateMemory(int **goals, int** assists, char*** names, int size)
{
    *goals = malloc(sizeof(int)* size);
    *assists = malloc(sizeof(int)* size);
    *names = malloc(sizeof(char*)* MAX_NAME);
}
int countLinesInFile(FILE* fptr)
{
    int i;
    char line[MAX_LINE];
    i = 0;
    while(fgets(line, MAX_LINE, fptr) != NULL)
    {
    i++;
    }
    rewind(fptr);
    return i;
}

--插入--

输入文件如下所示：Redden 2 0Berglund 5 2杰克曼2 0斯图尔特4 0Oshie 3 5麦当劳2 4Pietrangelo 2 7Perron 2 6Tarasenko 5 5

Answer 1

在allocateMemory（）中，每个*names都是一个char **。您需要分配两次

*names = malloc(...);
for (<each pointer in names>) {
    <pointer> = malloc(...);
}

别忘了免费两次太

for (<each pointer in names>) {
    free(<pointer>);
}
free(*names);

Answer 2

关于分段错误，您正在取消引用指针**names，但*names是一个统一的指针。这会导致未定义的行为，因此在您的情况下会出现执行错误（这可能是最糟糕的！）。要解决这个问题，您必须分配一个二维数组，例如：

*a = malloc(numLines * sizeof **a);
for (i = 0; i < n; i++) (*a)[i] = malloc(NAME);

此外，您的strtok使用似乎是错误的。这个函数保持一个指向数据的静态指针（因此它通常不是线程安全的）：您应该在接下来的调用中使用值NULL。否则，它每次都会返回相同的地址。在您喜欢的网络搜索引擎中键入man strtok，查看文档。

char line[MAX_LINE];
int i;
for (i = 0; i < numLines; i++)
{
    fgets(line, sizeof line, fptr);
    value = strtok(line, " ");
    (*names)[i] = atoi(value); /* This assignment looks strange. */
    value = strtok(NULL, " ");
    goals[i] = atoi(value);
    value = strtok(NULL, " ");
    assits[i] = atoi(value);
}

不要忘记数组下标运算符！如果是一个真实世界的程序，sscanf看起来更合适。