使用 sscanf 解析/标记 csv 文件？

Question

我目前正在尝试使用

sscanf

解析 .csv 文件。我制作了一个函数来检测行首的引号。

int checkString(const char *str) {
    if (str[0] == '"') {
        return 1;
    }
    return 0;
}

我需要解析文件的帮助，特别是因为 csv 文件的格式各不相同。

这是我尝试使用

sscanf

解析文件

int main() {
    char inputLine[100]; //input line
    Node *pList = NULL; //initialize linked list
    FILE *inputStream = fopen("../musicPlayList.csv", "r");
    Record testArr[100];
    Record inputRecord;
    Duration inputDuration;
    int inputTimesPlayed = 0;
    int inputRating = 0;

    char artistToken[20];
    char albumTitleToken[20];
    char songTitleToken[20];
    char genreToken[20];
    char durationToken[20];
    char timesPlayedToken[20];
    char ratingToken[20];

    if (inputStream != NULL) {
        while (fgets(inputLine, sizeof(inputLine), inputStream) != NULL) {
            if (checkString(inputLine)) {
                sscanf(inputLine, "\"%[^\"]\" %s %s %s %s %s %s",
                       artistToken, albumTitleToken,
                       songTitleToken, genreToken, durationToken,
                       timesPlayedToken, ratingToken);
            } else {
                sscanf(inputLine, "%s %s %s %s %s %s %s",
                       artistToken, albumTitleToken,
                       songTitleToken, genreToken, durationToken,
                       timesPlayedToken, ratingToken);
            }
            printf("%s %s %s %s %s %s %s\n",
                   artistToken, albumTitleToken, songTitleToken,
                   genreToken, durationToken, timesPlayedToken,
                   ratingToken);
        }
    }

    return 0;
}

这是 .csv 文件：

"Swift, Taylor",1989,Shake it Off,Pop,3:35,12,3
Drake,NOTHING WAS THE SAME,Own it,Rap,3:23,3,3
Drake,YOU WELCOME,The Motto,Rap,4:13,7,4
"Perri, Christina",HEAD OF HEART,Trust,Pop,2:35,3,5
"Bieber, Justin",PURPOSE,No Sense,Pop,4:12,6,1
Eminem,SHADYXV,Vegas,Rap,3:37,8,3
Adele,25,Remedy,Pop,4:11,24,4
"Swift, Taylor",RED,Stay Stay Stay,Pop,4:42,5,1
"Brooks, Garth",FRESH HORSES,The Old Stuff,Country,2:57,11,2

这是：

Swift, Taylor ,1989 , Shake it Off, Pop, 3:35,12,3 00doA
Drake, NOTHING WAS THE SAME, Own it, Rap, 3:23,3, 3
Drake, YOU WELCOME, The Motto, Rap, 4:13,7,4 SAME, Own it, Rap, 3:23,3,3
Perri, Christina ,HEAD ,3,5 HEART, Trust, Pop,2:35,3,5 it, Rap, 3:23,3,3
Bieber, Justin ,PURPOSE, No Sense, Pop, 4:12,6,1 HEART, Trust, Pop, 2:35Sense, Pop, 4:12,6,1 it, Rap, 3:23, 3, 3
Eminem, SHADYXV, Vegas, Rap, 3:37,8,3 , PURPOSE, No Sense, Pop, 4:12,6,1 HEART, Trust, Pop, 2:35Sense, Pop, 4:12,6,1 it, Rap, 3:23,3, 3
Adele, 25, Remedy, Pop, 4:11, 24,4 , PURPOSE, No Sense, Pop, 4:12,6,1 HEART, Trust, Pop, 2:35Sense, Pop, 4:12,6,1 it, Rap, 3:23,3 , 3
Swift, Taylor ,RED, Stay Stay Stay, Pop, 4:42,5,1 it, Rap, 3:23,3, 3
Brooks, Garth ,FRESH HORSES, The 1,2 Stuff, Country,2:57, 11, 2

Process finished with exit code 0

为什么它返回垃圾值，例如

00doA

。

Answer 1

sscanf

可以用来解析CVS行，但它是一个非常棘手的工具，有很多缺点。您的代码有问题：

• 您没有传递要存储到目标数组的最大字符数，从而导致潜在的缓冲区溢出。事实上，专辑标题

  NOTHING WAS THE SAME

  有 20 个字符，它不适合 20 个

  char

  的数组，因为

  sscanf

  将在字符串末尾存储一个空终止符。使数组更大并在

  %

  和转换说明符之间传递字符计数。
• format

  %s

  解析由空格分隔的单词，您需要

  %19[^,]

  的格式来解析由逗号分隔的字段。

• sscanf

  将无法解析空字段
• 您必须检查

  sscanf()

  的返回值以检测格式错误或丢失的输入。如果任何字段解析不正确，则其余令牌未修改，可能未初始化，这可以解释垃圾输出。

这是修改后的版本：

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

int main(void) {
    char inputLine[200]; //input line

    //Node *pList = NULL;
    //Record testArr[100];
    //Record inputRecord;
    //Duration inputDuration;
    //int inputTimesPlayed = 0;
    //int inputRating = 0;

    char artistToken[30];
    char albumTitleToken[30];
    char songTitleToken[30];
    char genreToken[20];
    char durationToken[20];
    char timesPlayedToken[20];
    char ratingToken[20];
    char eol[2];

    const char *filename = "musicPlayList.csv";
    int lineno = 0;
    FILE *inputStream = fopen(filename, "r");
    if (inputStream == NULL) {
        fprintf(stderr, "Cannot open %s: %s\n", filename, strerror(errno));
        return 1;
    }
    while (fgets(inputLine, sizeof(inputLine), inputStream) != NULL) {
        lineno++;
        if (sscanf(inputLine, "\"%29[^\"]\",%29[^,],%29[^,],%19[^,],%19[^,],%19[^,],%19[^,\n]%1[\n]",
                   artistToken, albumTitleToken, songTitleToken, genreToken,
                   durationToken, timesPlayedToken, ratingToken, eol) == 8
        ||  sscanf(inputLine, "%29[^,],%29[^,],%29[^,],%19[^,],%19[^,],%19[^,],%19[^,\n]%1[\n]",
                   artistToken, albumTitleToken, songTitleToken, genreToken,
                   durationToken, timesPlayedToken, ratingToken, eol) == 8)
        {
            printf("%s|%s|%s|%s|%s|%s|%s\n",
                   artistToken, albumTitleToken, songTitleToken, genreToken,
                   durationToken, timesPlayedToken, ratingToken);
        } else {
            printf("%s:%d: invalid format: %s\n", filename, lineno, inputLine);
        }
    }
    fclose(inputStream);
    return 0;
}

输出：

Swift, Taylor|1989|Shake it Off|Pop|3:35|12|3
Drake|NOTHING WAS THE SAME|Own it|Rap|3:23|3|3
Drake|YOU WELCOME|The Motto|Rap|4:13|7|4
Perri, Christina|HEAD OF HEART|Trust|Pop|2:35|3|5
Bieber, Justin|PURPOSE|No Sense|Pop|4:12|6|1
Eminem|SHADYXV|Vegas|Rap|3:37|8|3
Adele|25|Remedy|Pop|4:11|24|4
Swift, Taylor|RED|Stay Stay Stay|Pop|4:42|5|1
Brooks, Garth|FRESH HORSES|The Old Stuff|Country|2:57|11|2

但请注意，如果专辑标题或歌曲标题用双引号编码，特别是如果它包含嵌入的换行符，则此代码将失败。更先进的手工编码 CSV 解析器可以处理这些变化。