我有一个值为
的csv文件1,A,X
2,B,Y
3,C,Z
我必须逐行读取CSV文件并将其保存在Structure数组中。 每次在for循环中值都很好。但是在我打印数组的最后，只打印了最后一个值。 有人请告诉我我在哪里做逻辑错误？
struct proc
{
char *x;
char *y;
};
void main()
{
fflush(stdin);
fflush(stdout);
const char s[2] = ",";
char *token;
int rows=0,i,tokenVal=0,rowCount=0;
FILE *fpCount = fopen("data.csv","r");
if(fpCount != NULL)
{
char lineCount[20];
while(fgets(lineCount, sizeof lineCount, fpCount))
rows++;
}
struct proc *pi[rows];
for(i=0;i<rows;i++)
pi[i] = (struct proc*) malloc(sizeof(struct proc));
FILE *fp = fopen("data.csv", "r");
if(fp != NULL)
{
char line[20];
while(fgets(line, sizeof line, fp) != NULL)
{
printf("Start rowCount = %d\t",rowCount);
token = strtok(line, s);
while(token!=NULL)
{
if(tokenVal==0)
{
pi[rowCount]->Id =token;
}
if(tokenVal==1)
{
pi[rowCount]->act = token;
}
printf("\n");
tokenVal++;
token = strtok(NULL,s);
}
tokenVal = 0;
printf("end rowCount = %d\t",rowCount);
rowCount++;
}
fclose(fp);
} else {
perror("data.csv");
}
printf("total %d",rowCount);
int k=0;
for(k=0;k<rowCount;k++)
{
printf(" %d = %s----%s",k,pi[k]->Id,pi[k]->act);
}
}
答案 0 :(得分：0)
在 printf（“％d =％s ----％s ----％s”，k，pi [k] - ＆gt; Id，pi [k] - ＆gt; act） 有四个数据 ％d ％S ％S ％S
但你只设置了三个 ķ PI [K] - ＆GT;标识 PI [K] - ＆GT;行为
答案 1 :(得分：0)
您面临的根本问题是您在结构中保存指向变量line的指针，但每个新行都会覆盖line中之前的内容，所以最后只有来自最后一行存在。你的数据线都是'形状'是偶然的;如果字段长度不同，那么你会得到更多有趣但同样错误的结果。
因此，您需要保存每个字段的副本，而不仅仅是指向字段的指针。使用POSIX函数strdup()的简单方法是使用POSIX函数What should main() return in C and C++?。如果您没有该功能，可以创建它：
char *strdup(const char *str)
{
size_t len = strlen(str) + 1;
char *rv = malloc(len);
if (rv != 0)
memmove(rv, str, len); // or memcpy
return rv;
}
您的代码无法编译;您的数据结构包含元素x和y，但您的代码使用元素Id和act。你使用指向你的struct proc的指针的VLA，但是分配一个结构数组是合理的，无论是作为VLA还是通过malloc()等。您应该检查内存分配 - 但是没有办法检查VLA（使用动态分配的一个原因）。您可以回放文件而不是重新打开它。 （使用变量保存文件名是个好主意，即使你只打开一次;它会使错误报告更好。另外，错误应该会停止程序，一般来说，尽管你确实使用了perror()重新打开操作失败 - 但是如果打开失败则不会。）您不需要两个数组来读取行。对输入线使用更长的缓冲区是个好主意。你应该释放动态分配的内存。另请参阅https://jsfiddle.net/7fo28qrd/;答案是int而不是void（除非你在Windows上）。
以下是您的代码的三种变体，上面列出的问题的各个方面或多或少已修复。
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct proc
{
char *x;
char *y;
};
int main(void)
{
const char datafile[] = "data.csv";
const char csv_delim[] = ",\n";
int rows = 0, rowCount = 0;
FILE *fpCount = fopen(datafile, "r");
if (fpCount == NULL)
{
fprintf(stderr, "Failed to open '%s' for reading\n", datafile);
exit(EXIT_FAILURE);
}
char lineCount[2000];
while (fgets(lineCount, sizeof(lineCount), fpCount))
rows++;
fclose(fpCount);
printf("Read %d rows from '%s'\n", rows, datafile);
struct proc *pi[rows];
for (int i = 0; i < rows; i++)
pi[i] = (struct proc *)malloc(sizeof(struct proc));
FILE *fp = fopen(datafile, "r");
if (fp == NULL)
{
fprintf(stderr, "Failed to reopen '%s' for reading\n", datafile);
exit(EXIT_FAILURE);
}
char line[2000];
while (fgets(line, sizeof(line), fp) != NULL)
{
printf("Start rowCount = %d\t", rowCount);
int tokenVal = 0;
char *token = strtok(line, csv_delim);
while (token != NULL)
{
if (tokenVal == 0)
{
pi[rowCount]->x = strdup(token);
}
else if (tokenVal == 1)
{
pi[rowCount]->y = strdup(token);
}
printf("[%s]", token);
tokenVal++;
token = strtok(NULL, csv_delim);
}
printf("\tend rowCount = %d\n", rowCount);
rowCount++;
}
fclose(fp);
/* Data validation */
printf("total %d\n", rowCount);
for (int k = 0; k < rowCount; k++)
{
printf("%d = [%s]----[%s]\n", k, pi[k]->x, pi[k]->y);
}
/* Release allocated memory */
for (int k = 0; k < rowCount; k++)
{
free(pi[k]->x);
free(pi[k]->y);
free(pi[k]);
}
return 0;
}
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct proc
{
char *x;
char *y;
};
int main(void)
{
const char datafile[] = "data.csv";
const char csv_delim[] = ",\n";
int rows = 0, rowCount = 0;
FILE *fpCount = fopen(datafile, "r");
if (fpCount == NULL)
{
fprintf(stderr, "Failed to open '%s' for reading\n", datafile);
exit(EXIT_FAILURE);
}
char lineCount[2000];
while (fgets(lineCount, sizeof(lineCount), fpCount))
rows++;
fclose(fpCount);
printf("Read %d rows from '%s'\n", rows, datafile);
struct proc pi[rows];
FILE *fp = fopen(datafile, "r");
if (fp == NULL)
{
fprintf(stderr, "Failed to reopen '%s' for reading\n", datafile);
exit(EXIT_FAILURE);
}
char line[2000];
while (fgets(line, sizeof(line), fp) != NULL)
{
printf("Start rowCount = %d\t", rowCount);
int tokenVal = 0;
char *token = strtok(line, csv_delim);
while (token != NULL)
{
if (tokenVal == 0)
{
pi[rowCount].x = strdup(token);
}
else if (tokenVal == 1)
{
pi[rowCount].y = strdup(token);
}
printf("[%s]", token);
tokenVal++;
token = strtok(NULL, csv_delim);
}
printf("\tend rowCount = %d\n", rowCount);
rowCount++;
}
fclose(fp);
/* Data validation */
printf("total %d\n", rowCount);
for (int k = 0; k < rowCount; k++)
{
printf("%d = [%s]----[%s]\n", k, pi[k].x, pi[k].y);
}
/* Release allocated memory */
for (int k = 0; k < rowCount; k++)
{
free(pi[k].x);
free(pi[k].y);
}
return 0;
}
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct proc
{
char *x;
char *y;
};
int main(void)
{
const char datafile[] = "data.csv";
const char csv_delim[] = ",\n";
int num_rows = 0, rowCount = 0;
FILE *fp = fopen(datafile, "r");
if (fp == NULL)
{
fprintf(stderr, "Failed to open '%s' for reading\n", datafile);
exit(EXIT_FAILURE);
}
char line[2000];
while (fgets(line, sizeof(line), fp))
num_rows++;
rewind(fp);
printf("Read %d rows from '%s'\n", num_rows, datafile);
struct proc *pi = calloc(num_rows, sizeof(*pi));
if (pi == 0)
{
fprintf(stderr, "Failed to allocate %zu bytes of memory\n", num_rows * sizeof(*pi));
exit(EXIT_FAILURE);
}
while (fgets(line, sizeof(line), fp) != NULL)
{
printf("Start rowCount = %d\t", rowCount);
int tokenVal = 0;
char *token = strtok(line, csv_delim);
while (token != NULL)
{
if (tokenVal == 0)
{
pi[rowCount].x = strdup(token);
// null check
}
else if (tokenVal == 1)
{
pi[rowCount].y = strdup(token);
// null check
}
printf("[%s]", token);
tokenVal++;
token = strtok(NULL, csv_delim);
}
printf("\tend rowCount = %d\n", rowCount);
rowCount++;
}
fclose(fp);
/* Data validation */
printf("total %d\n", rowCount);
for (int k = 0; k < rowCount; k++)
{
printf("%d = [%s]----[%s]\n", k, pi[k].x, pi[k].y);
}
/* Release allocated memory */
for (int k = 0; k < rowCount; k++)
{
free(pi[k].x);
free(pi[k].y);
}
free(pi);
return 0;
}
给定一个数据文件：
1,A,X
2,B,Y
3,C,Z
3192-2146-9913,Abelone,Zoophyte
所有三个程序都产生相同的输出：
Read 4 rows from 'data.csv'
Start rowCount = 0 [1][A][X] end rowCount = 0
Start rowCount = 1 [2][B][Y] end rowCount = 1
Start rowCount = 2 [3][C][Z] end rowCount = 2
Start rowCount = 3 [3192-2146-9913][Abelone][Zoophyte] end rowCount = 3
total 4
0 = [1]----[A]
1 = [2]----[B]
2 = [3]----[C]
3 = [3192-2146-9913]----[Abelone]