从C中的txt文件中读取下一行

Question

我在下面创建了代码，它从 data.txt 文件读取并将每个字符拆分到数组中。现在它只读取 data.txt 中的第一行。我怎样才能让它循环并读取下一行？

有人可以告诉我需要添加什么吗？

data.txt 文件的内容

 O7550x
 N9300x
 H51200

这是我现有的代码：

#include<stdio.h>
int main()
{
printf("Product code: ");
char a[6];
int i=0;


FILE *fptr;
fptr=fopen("data.txt", "r");
   
while((a[i++]=getc(fptr)) != '\n' && i < 6);

if(a[0] >= 'A' && a[0] <= 'Z')
{
if (a[0]=='O')
{
    printf("State: Ohio");
}
else if (a[0]=='I'||a[0]=='H')
{
    printf("State: Hawaii");
}
else if (a[0]=='N')
{
    printf("State: New York");
}
else
{
    printf("State: Unknown");
}
    printf("\n");
if (a[1]=='5')
{
    printf("Stores: Five");
}
else if (a[1]=='7')
{
    printf("Stores: Seven");
}
else if (a[1]=='9')
{
    printf("Stores: Nine");
}
else
{
   printf("Stores: Unknown");
}
   printf("\n");
if (a[2]=='3'&&a[3]=='0'&&a[4]=='0')
{
    printf("Inventory: 300 units");
}
else if (a[2]=='5'&&a[3]=='5'&&a[4]=='0')
{
    printf("Inventory: 500 units");
}
else if (a[2]=='1'&&a[3]=='2'&&a[4]=='0'&&a[5]=='0')
{
    printf("Inventory: 1200 units");

}
else
{
   printf("Inventory: Unknown");
}

}
else
   printf("Invalid code");
     return 0;
}

Answer 1

我不确定这是否是您想要做的事情，但下面的代码可以同时读取命令行输入和 txt 文件。但是，您无法使用此代码循环遍历所有元素。为此，您需要读取行数并动态分配内存并将每行存储在动态创建的数组的第二个维度中。

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

void printProductCode(char*);
int numberOfLines(FILE*);
void display_array(char**, int, int);

int main()
{
    int flag, sizeOfFile = 0, readFrom = 0;
    char **b;
    char a[6];
    int i=0;
    FILE *fptr;

    do {
        flag = 1;
        printf("Which way you will enter the product code? (Command-Line: 1), (File: 2) ");
        scanf("%d",&readFrom);

        if(readFrom == 1) {
            printf("Product code: ");
            getchar();
            while((a[i++]=getchar()) != '\n' && i < 6);
        } else if(readFrom == 2) {
            int j = 0;
            fptr=fopen("data.txt", "r");

            sizeOfFile = numberOfLines(fptr);
            b = (char**)malloc(sizeOfFile * sizeof(char*));

            for (int i = 0;i < sizeOfFile;i++) {
                b[i] = (char*)malloc(6 * sizeof(char));
            }

            while(fscanf(fptr, "%s", b[j++]) != EOF);
        } else {
            printf("Please enter valid input!");
            flag = 0;
        }
    } while(flag == 0);

    if (readFrom == 1) {
        printProductCode(a);
    }
    else if(readFrom == 2){
        for(int i = 0;i < sizeOfFile;i++) {
            printProductCode(b[i]);
        }

        //Freeing could done with a different if statement because
        //we may want to use b in the following steps, but for
        //simplicity I freed the memory here for now on.
        for(int i=0;i<sizeOfFile;i++) {
            free(b[i]);
        }
        free(b);
    }



    return 0;
}

void printProductCode(char* a) {
    if(a[0] >= 'A' && a[0] <= 'Z')
    {
        if (a[0]=='O')
        {
            printf("State: Ohio");
        }
        else if (a[0]=='I'||a[0]=='H')
        {
            printf("State: Hawaii");
        }
        else if (a[0]=='N')
        {
            printf("State: New York");
        }
        else
        {
            printf("State: Unknown");
        }
        printf("\n");
        if (a[1]=='5')
        {
            printf("Stores: Five");
        }
        else if (a[1]=='7')
        {
            printf("Stores: Seven");
        }
        else if (a[1]=='9')
        {
            printf("Stores: Nine");
        }
        else
        {
           printf("Stores: Unknown");
        }
        printf("\n");
        if (a[2]=='3'&&a[3]=='0'&&a[4]=='0')
        {
            printf("Inventory: 300 units");
        }
        else if (a[2]=='5'&&a[3]=='5'&&a[4]=='0')
        {
            printf("Inventory: 500 units");
        }
        else if (a[2]=='1'&&a[3]=='2'&&a[4]=='0'&&a[5]=='0')
        {
            printf("Inventory: 1200 units");

        }
        else
        {
           printf("Inventory: Unknown");
        }
    }
    else
       printf("Invalid code");
    printf("\n\n");
}

int numberOfLines(FILE* fp) {
    int counter = 0;
    char c = fgetc(fp);
    while(c != EOF) {
        c = fgetc(fp);
        if (c == '\n'){
            counter++;
        }
    }
    rewind(fp);
    return (counter + 1);
}

void display_array(char** arr, int r, int c) {
    for(int i = 0;i<r;i++) {
        for(int j = 0;j < c;j++) {
            printf("%c", arr[i][j]);
        }
        printf("\n");
    }

}

另外，这是您需要为此代码提供的文本文件。

O7550x
N9300x
H51200

祝你好运！

我以一种可以读取所有行并打印结果的方式编辑了代码。