在 C 中的 strtok 之后无法正确计算 CSV 中的元素

Question

在我使用 strtok 以逗号和引号（双引号）分隔后，我有时只会看到正确的元素数量。通常 printf 的长度为 0，但偶尔为 6 和 1，代码没有变化。

我尝试只使用一个分隔符（逗号）并以不同的方式定义 strtok 的标记输出，并重新排列 while 循环中的语句顺序，其中该行的其他元素被认为是分隔的。这些是我用来测试代码 (test.csv) 的 .csv 文件的几行。它与 NOAA 以 .csv 格式提供降水数据的格式相同。

"STATION","NAME","DATE","PRCP","PRCP_ATTRIBUTES"
"US183459384","XYZ ABC 9.0 E, WA US","2019-01-06","0.65",",,N"
"US183459384","XYZ ABC 9.0 E, WA US","2019-01-12","0.46",",,N"
"US183459384","XYZ ABC 9.0 E, WA US","2019-01-13","0.09",",,N"
"US183459384","XYZ ABC 9.0 E, WA US","2019-01-14","0.01",",,N"
"US183459384","XYZ ABC 9.0 E, WA US","2019-01-15","0.60",",,N"
"US183459384","XYZ ABC 9.0 E, WA US","2019-01-16","1.93",",,N"

我的代码尝试如下。

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

#define BUFFER_SIZE 1024

int get_row(FILE *file, int row_num, char delim[]) {
    int n_line = 0;
    int field = 0;
    char row[BUFFER_SIZE], *line[BUFFER_SIZE];

    while (fgets(row, BUFFER_SIZE, file)) {
        if (n_line == row_num) {
            printf("Length of line %d is %ld elements!\n", n_line, strlen(row));
            char* element = strtok(row, delim);
            while (element != NULL) {
                printf("%s\n", element);
                line[field++] = strdup(element);
                element = strtok(NULL, delim);
            }
            return 0;
        } else {
          n_line++;
    }
    printf("There is no row %d in the file you selected.\n", row_num);
    return 0;
}

int main(int argc, char **argv) {
    FILE *file;
    char delim[]  = ", \"";

    file = fopen(”test.csv”, "r");
    if (!file) {
        printf("Error: could not open %s\n", file_name);
        return -1;
    }
    printf("Reading file...\n");
    get_row(file, 0, delim);
    fclose(file);
    return 0;
}

我希望结果显示为 5，但所有行的结果为 0 或 1，偶尔为 6。

Answer 1

此程序不应编译，因为未定义 file_name。 此外，在 getrow 函数内部，没有元素应该等于字段，而不是缓冲区的长度。由于该字段中有逗号，因此逗号分隔符也不起作用。 以下代码适用于 test.csv 文件中的给定行

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

#define BUFFER_SIZE 1024

int get_row(FILE *file, int row_num, char delim[]) {
    int n_line = 0;
    int field = 0;
    char row[BUFFER_SIZE], *line[BUFFER_SIZE];

    while (fgets(row, BUFFER_SIZE, file)) {
        if (n_line == row_num) {
            char* element = strtok(row, delim);
            while (element != NULL) {
                if(strcmp(",", element) != 0 &&  strcmp("\n", element) != 0)
                {
                  printf("%s\n", element);
                  line[field++] = strdup(element);
                }
                element = strtok(NULL, delim);
            }
            printf("Length of line %d is %d elements!\n", n_line, field);
            return 0;
        } else {
          n_line++;
    }
  }
    printf("There is no row %d in the file you selected.\n", row_num);
    return 0;
}

int main(int argc, char **argv) {
    FILE *file;
    char delim[]  = "\"";
    char file_name[] = "test.csv";

    file = fopen(file_name, "r");
    if (!file) {
        printf("Error: could not open %s\n", file_name);
        return -1;
    }
    printf("Reading file...\n");
    get_row(file, 0, delim);
    fclose(file);
    return 0;
}

Answer 2

程序中有许多语法错误。 这应该有效：

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

#define BUFFER_SIZE 1024

int get_row(FILE *file, int row_num, char delim[]) {
    char row[BUFFER_SIZE];

    for (int i = 0; fgets(row, BUFFER_SIZE, file); i++) {
        if (i == row_num) {
            printf("Length of line %d is %ld elements!\n", i, strlen(row));

            char* element = strtok(row, delim);
            while (element) {
                printf("%s\n", element);
                element = strtok(NULL, delim);
            }

            break;
        }
    }

    printf("There is no row %d in the file you selected.\n", row_num);

    return 0;

}

int main() {
    FILE *file;
    char delim[]  = ", \"";

    file = fopen("test.csv", "r");
    if (!file) {
        puts("Error: could not open");
        return -1;
    }

    printf("Reading file...\n");
    get_row(file, 0, delim);
    fclose(file);

    return 0;
}