使用fscanf逐行遍历FILE

Question

好的,我有一个文本文件database.txt.

每行都是具有以下格式的用户

"John Smith"| 4| 80.00| "123 Lollipop Lane"| "New Jersey"| "08080"  

当我尝试执行以下操作时:

database = fopen(fileName,"r"); 
    while(fscanf(database,"%[^\n]", buffer) != EOF){ 
        printf("ATTEMPT TO: Insert user %s\n\n", buffer); 
        if (insert_Customer(clients, create_Customer(buffer)) < 0){ 
            printf("\nERROR: Failed to insert and create customer %s\n", buffer); 
        } 
        else printf("\nSUCCESS: Inserted Customer %s\n\n", buffer); 
    } 

它在第一行运行正常,将ENTIRE行发送到create_Customer(char*buffer)函数.出于某种原因,我不明白,在第一行之后它不断尝试发送"John Smith"而不是继续前进到下一行.我相信我的格式不正确,但我无法弄清楚如何完成我想要完成的工作,逐行读取此文件并将每行传递给create_Customer函数.

Answer 1

我认为你需要关闭\n你的模式.我看到了一堆带有相同第一行的滚动文本%[^\n],但是%[^\n]\n我看到了预期的输出.

但是,如果文件中的行超过缓冲区的行,则可能会遇到缓冲区空间不足的问题.结果

测试v1:

码

#include <stdio.h>


int main(int argc, char * argv[])
{
    FILE * database;
    char buffer[30];

    database = fopen("test.txt", "r");

    if (NULL == database)
    {
         perror("opening database");
         return (-1);
    }

    while (EOF != fscanf(database, "%[^\n]\n", buffer))
    {
         printf("> %s\n", buffer);
    }

    fclose(database);
    return (0);
}

结果

> 12343456567856789
> zbasdflkjasdfkjklsdafjklas
> zxcvjkleryjkldhfg
> 1234567890123456789012341234
> 12345678901234567890123123asdfjklzxcv;jkl;eqwrtjklkzlcxvjkleqrt41234
*** stack smashing detected ***: ./fscanf terminated                                                                                                                   
Segmentation fault (core dumped)

测试v2:

让我们修复代码,这样我们就不会超出缓冲区.我们通过改为%[^\n]\n来做到这一点%30[^\n]\n.这告诉fscanf它只能使用最大缓冲区大小 - 30.

码

#include <stdio.h>


int main(int argc, char * argv[])
{
    FILE * database;
    char buffer[30];

    database = fopen("test.txt", "r");

    if (NULL == database)
    {
         perror("opening database");
         return (-1);
    }

    while (EOF != fscanf(database, "%30[^\n]\n", buffer))
    {
         printf("> %s\n", buffer);
    }

    fclose(database);
    return (0);
}

结果

它看起来像是有效的!

> 12343456567856789
> zbasdflkjasdfkjklsdafjklas
> zxcvjkleryjkldhfg
> 1234567890123456789012341234
> 12345678901234567890123123asdf
> jklzxcv;jkl;eqwrtjklkzlcxvjkle
> qrt41234

的test.txt

这就是我正在使用的测试文件.

12343456567856789
zbasdflkjasdfkjklsdafjklas
zxcvjkleryjkldhfg
1234567890123456789012341234
12345678901234567890123123asdfjklzxcv;jkl;eqwrtjklkzlcxvjkleqrt41234

您正在使用的任何原因fscanf,而不是fgets？

如果您使用fgets,有一点需要注意,您可能想要删除该\n字符,因为它将作为字符串的一部分包含在内.

来自cplusplus.com fgets:

从流中读取字符并将它们作为C字符串存储到str中,直到读取(num-1)个字符或者到达换行符或文件结尾,以先发生者为准.

例:

/* fgets example */
#include <stdio.h>

int main()
{
    FILE * database;
    int res;
    char buffer [100];

    database = fopen(fileName,"r");

    if (NULL == database) {
        perror("opening database file");
        return (-1);
    }

    /* while not end-of-file */
    while (!feof(database)) { 

        /* we expect buffer pointer back if all is well, get out if we don't get it */
        if (buffer != fgets(buffer, 100, database))
            break;

        /* strip /n */
        int len = strlen(buffer);
        if (buffer[len - 1] == '\n')
            buffer[len - 1] = 0;

        printf("ATTEMPT TO: Insert user %s\n\n", buffer); 

        if (insert_Customer(clients, create_Customer(buffer)) < 0)
            printf("\nERROR: Failed to insert and create customer %s\n", buffer); 
        else
            printf("\nSUCCESS: Inserted Customer %s\n\n", buffer);
    }

    /* a little clean-up */
    fclose(database);

    return (0);
}