c - 尝试将 char 数组传递给函数

Question

我正在尝试将 char 数组传递给我正在创建的函数，以便我可以查看两个汽车 ID 是否相等。我正在创建的函数名为 mpg，它接受 char *id。如果传递给该函数的 ID 等于任何汽车的 ID，它会打印出 1。顺便说一句，该 ID 也是一个字符串。我对 C 编程非常陌生，所以任何帮助都会很好。有任何问题请追问。

汽车信息栏分别为号码、ID、里程表、加仑。

汽车信息

0 987654 201200 4.000000
1 red 89114 0.000000
2 red 89712 13.500000
3 red 90229 15.300000
4 987654 201001 0.000000
5 987654 201111 5.200000
6 987654 201612 25.299999
7 red 89300 7.100000
8 green 16 0.000000
9 green 216 20.000000
10 green 518 61.000000
11 green 879 50.000000

代码

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>
#define numberOfRecords 12

struct record
{
    char *id;
    int odometer;
    float gallons;
};
typedef struct record gasRecord;

gasRecord gasDataArray[numberOfRecords];

void mpg(char*);

int main(int argc, char *argv[])
{
    FILE *fileInput;
    float gallons;
    int   element, odometer;
    char  id[10];
    char  test[10] = {"987654"};

    fileInput = fopen("gasData.txt", "r");
    if (fileInput == NULL)
    {
        printf("cannot open `gasData.txt'\n");
        return -1;
    }

    for(element = 0; element < numberOfRecords; element++)
    {
        if(feof(fileInput))
        {
            printf("end-of-file detected on file\n");
            exit(1);
        }

        if (fscanf(fileInput, "%s %d %f", id, &odometer, &gallons) == 3)
        {
            gasDataArray[element].id = malloc (strlen(id)+1);
            strcpy(gasDataArray[element].id, id);
            gasDataArray[element].odometer = odometer;
            gasDataArray[element].gallons = gallons;

            printf("Record #: %d id = %s, odometer = %d, gallons = %f\n",
                   element, gasDataArray[element].id, gasDataArray[element].odometer, gasDataArray[element].gallons);
        }
    }

    printf("Test ID = %s\n", test);

    mpg(test);

    return 0;
}

void mpg(char *id)
{
    int i;

    for(i = 0; i < numberOfRecords; i++)
    {

        if (gasDataArray[i].id == id)
        {
            printf("1");
        }
    }
}

编辑代码

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

#define numberOfRecords 12

struct record
{
    char *id;
    int odometer;
    float gallons;
};
typedef struct record gasRecord;

gasRecord gasDataArray[numberOfRecords];

void mpg(char*);

int main(int argc, char *argv[])
{
    FILE *fileInput;
    float gallons;
    int   element, odometer;
    char  id[10];
    char  test[10] = {"red"};

    fileInput = fopen("gasData.txt", "r");
    if (fileInput == NULL)
    {
        printf("cannot open `gasData.txt'\n");
        return -1;
    }

    for(element = 0; element < numberOfRecords; element++)
    {
        if(feof(fileInput))
        {
            printf("end-of-file detected on file\n");
            exit(1);
        }

        if (fscanf(fileInput, "%s %d %f", id, &odometer, &gallons) == 3)
        {
            gasDataArray[element].id = malloc (strlen(id)+1);
            strcpy(gasDataArray[element].id, id);
            gasDataArray[element].odometer = odometer;
            gasDataArray[element].gallons = gallons;

            printf("Record #: %d id = %s, odometer = %d, gallons = %f\n",
                   element, gasDataArray[element].id, gasDataArray[element].odometer, gasDataArray[element].gallons);
        }
    }

    printf("Test ID = %s\n", test);

    mpg(test);

    return 0;
}

void mpg(char *id)
{
    int i, minMile = 0, maxMile = 0;

    for(i = 0; i < numberOfRecords; i++)
    {

        if (strcmp(id, gasDataArray[i].id))
        {
            printf("1");
        }
    }
}

Answer 1

在 C 语言中，您无法将字符串与 == 进行比较。 – alain

我刚刚使用了 strcmp，它运行得很好。我太习惯 C++ 了，所以这种编程对我来说是新的。谢谢阿兰 - 约翰尼·安德烈