如何从csv文件中获取特定的行? [英] how to get specific rows from csv file?

问题描述

我已经编写了一个代码，其中我试图获取从"A" 开始的所有行.我的csv文件中有A，A12等，我想读取所有这些行.但是我得到了以下错误.不知道我哪里做错了.请帮助.

I've written a code, wherein i'm trying to get all the rows which start from "A". I have A, A12 etc in my csv file and i want to read all those rows. But i got the following error. Not sure where i went wrong. Kindly help.

CSV文件

M,2,lion
A,1,tiger
B,2,cat
A1,7,dog
C,3,man
A2,9,mouse
A23,9,pouch

myfile.c

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

#define NUMLETTERS 100

typedef struct {
    char letter[100];
    int number;
    char ani[100];
} record_t;

int main(void) {
    FILE *fp;
    record_t records[NUMLETTERS];
    size_t count = 0;

    fp = fopen("letters.csv", "r");
    if (fp == NULL) {
        fprintf(stderr, "Error reading file\n");
        return 1;
    }

    while (fscanf(fp, " %s,%d,%s", records[count].letter, &records[count].number, records[count].ani) == 3) {
        count++;
    }

    for (size_t i = 0; i < count; i++) {
        if(records[i].letter== "A"){
        printf("%s,%d,%s\n", records[i].letter, records[i].number,records[i].number);
    }
    }

    fclose(fp);

    return 0;
} 

错误

myfile.c:29:16: warning: format ‘%s’ expects argument of type ‘char *’, but argument 4 has type ‘int’ [-Wformat=]
         printf("%s,%d,%s\n", records[i].letter, records[i].number,records[i].number);

推荐答案

由于您搜索以A开头的字段，因此只需要比较letter的第一个字母，因此第28行变为:

Since you search fields that start with A, you only need to compare the first letter of letter, so your line 28 becomes:

if(records[i].letter[0] == 'A'){

编译器告诉您，您尝试将整数显示为字符串，这是因为在第29行中有一个错字:number而不是ani，该行应为:

And your compiler told you that you try to display an integer as a string, it's because you have a typo in line 29: number instead of ani, the line should be:

printf("%s,%d,%s\n", records[i].letter, records[i].number,records[i].ani);

对不起，我得到了我的输出，但是在输出中添加了一些额外的列，分别为"0" A，1，tiger，0，A1,7，dog，0，A2,9，mouse，0，A23,9，pouch， 0，– Abhik 2小时前

Sorry i got my output but some extra column added in my output as "0" A,1,tiger,0, A1,7,dog,0, A2,9,mouse,0, A23,9,pouch,0, – Abhik 2 hours ago

它来自您的scanf调用:在scanf中，%s将读取直到找到一个空格(空格，制表符或换行符).找到第一个逗号后，您必须告诉scanf停止读取letter.为此，将%s替换为%99[^,].此处提供更多说明: Scanf指南.

It comes from your scanf call: in scanf, %s will read until in find a space (space or tab or line feed). You have to tell to scanf to stop too read letter after the first comma found. To do this, replace %s with %99[^,]. More explanations here: Scanf guide.

因此您的阅读循环应如下所示:

So your reading loop should looks like:

while (fscanf(fp, " %99[^,],%d,%s", records[count].letter, &records[count].number, records[count].ani) == 3) {
    count++;
}

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