在过去的两天里，我问了一个question to load struct，但是我有一个问题是我的循环访问我的结构（一个循环来加载我的结构）。我已经用这种方式编辑了我的问题/代码：
myfile.txt的
Biology,chemistry,maths,music
Mechanics,IT,Geology,music,Astronomy
football,vollyball,baseball
的main.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define path "myfile.txt"
typedef struct student_info
{
char **cources_as_list;
} std_info;
std_info *myinfo; //a global var that will conatain student info
int line_count = 0, cource_count = 0;
char** load_file()
{
char *line = NULL;
size_t len = 0;
FILE *fp;
int indexq=0;
fp = fopen(path, "r");
if (fp == NULL)
{
perror("FILE OPEN ERROR[IN load_file]: ");
exit(1);
}
char **mydata = malloc (sizeof (char *) * 4);//aup to four elements
while (getline(&line, &len, fp) != -1)
{
strtok(line, "\n");
mydata[indexq]= strdup(line);
indexq++;
}
line_count = indexq;
return mydata;
}
char **return_cource_list(char *cources_string) {
char *token;
char **cource_list = malloc(sizeof(char *) * 10);
int index = 0;
//course_string is delimited by ",": (eg. Biology,chemistry,maths,music). parse this and add to my char ** variable.
token = strtok(cources_string, ",");
while (token != NULL)
{
cource_list[index] = strdup(token);
token = strtok(NULL, ",");
index++;
}
cource_count = index;
return cource_list;
}
int main()
{
int i, j;
char** mydata = load_file(); //returns lines as a list/char ** array from file
for (i = 0; i < line_count; i++) //line_count is the number of elements/lines in "mydata"
{
printf("line_data: %s\n",mydata[i]);//i can see all my lines!
char **std_cource_list = return_cource_list(mydata[i]);
for (j = 0; j < cource_count; j++)
{
printf("\tcourse[%d]: %s\n",j,std_cource_list[j]);//i have all my courses as a list from each line
}
//can i load my struct like this? or any option to load my struct?
myinfo[i].cources_as_list = std_cource_list;
}
// i want to see my structure elements here, (nested for loop required).
}
将我的char数组加载到我的struct时遇到seg_fault错误。
（即：这一行：myinfo[i].cources_as_list = std_cource_list;）
答案 0 :(得分：0)
您需要为结构分配内存。
std_info *myinfo = malloc(sizeof(std_info));
另外，不要将其设为全局，因为此任务中确实不需要全局变量。
答案 1 :(得分：0)
尝试
std_info * myinfo = malloc(line_count * sizeof *myinfo);
这会分配内存来保存line_count的{{1}}个对象，std_info指向第一个。
答案 2 :(得分：-1)
您永远不会为myinfo分配空间，我建议将其作为局部变量。除非在非常具体的情况下，几乎不需要全局变量。
此外，您正在使用malloc()几乎仅用于固定大小的分配，如果您可以使用数组进行静态处理，那么这将更容易管理并且效率更高。
这可能是您对
感兴趣的内容#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stddef.h>
struct student_info
{
char **courses;
size_t size;
};
char **
load_file(const char *const path)
{
char *line;
FILE *file;
char **data;
size_t row;
size_t length;
size_t count;
file = fopen(path, "r");
if (file == NULL)
{
perror("FILE OPEN ERROR[IN load_file]: ");
return NULL; // Notify the caller that there was a problem
// but do not necessarily quit as you might
// retry with another path.
}
count = 0;
for (int chr = fgetc(file) ; chr != EOF ; chr = fgetc(file))
count += (chr == '\n') ? 1 : 0;
rewind(file);
data = malloc((count + 1) * sizeof(*data));
if (data == NULL)
{
// Perhaps notify the error
fclose(file);
return NULL;
}
data[count] = NULL; // Use as end of array delimiter
row = 0;
line = NULL;
length = 0;
while ((length = getline(&line, &length, file)) != -1)
{
// The last character is always `\n' so remove it
data[row] = malloc(length);
if (data == NULL)
{
fclose(file);
for (size_t i = row ; i >= 0 ; --i)
{
free(data[i]);
free(data);
return NULL;
}
}
data[row][length - 1] = '\0';
memcpy(data[row], line, length - 1);
++row;
}
fclose(file);
// You need to `free' this, read the documentation
free(line);
return data;
}
char **
extract_courses_as_list(const char *const input)
{
char **courses;
size_t index;
const char *tail;
const char *head;
size_t count;
head = input;
count = 0;
/* Count the number of fields to allocate memory */
while (head != NULL)
{
tail = strchr(head, ',');
if (tail != NULL)
head = tail + 1;
else
head = NULL;
count += 1;
}
index = 0;
/* Allocate memory for the list, and the sentinel */
courses = malloc((count + 1) * sizeof(*courses));
head = input;
while (head != NULL)
{
ptrdiff_t length;
/* find the next `,' in the input string */
tail = strchr(head, ',');
if (tail == NULL) /* if it's not there, it's the last one */
tail = strchr(head, '\0');
/* compute the number of characters of the field */
length = (ptrdiff_t) (tail - head);
/* allocate space to copy the string */
courses[index] = malloc(length + 1);
if (courses == NULL) /* always be safe and check */
{
for (size_t i = index ; i >= 0 ; --i)
free(courses[index]);
free(courses);
return NULL;
}
/* always remember to `null' terminate */
courses[index][length] = '\0';
/* finally, copy the string */
memcpy(courses[index], head, length);
/* check whehter it was the last field and
* update the pointer to the next one accordingly
*/
if ((tail != NULL) && (*tail != '\0'))
head = tail + 1;
else
head = NULL;
/* Don't forget the fields counter */
index++;
}
courses[count] = NULL;
return courses;
}
void
concatenate_lists(struct student_info *info, char **source)
{
char **temporary;
size_t length;
length = info->size;
for (size_t i = 0 ; source[i] != NULL ; ++i)
length++;
temporary = realloc(info->courses, length * sizeof(*temporary));
if (temporary == NULL)
return;
for (size_t i = 0 ; source[i] != NULL ; ++i)
temporary[i + info->size] = strdup(source[i]);
info->courses = temporary;
info->size = length;
}
void
free_list(char **lines)
{
if (lines == NULL)
return;
for (size_t i = 0 ; lines[i] != '\0' ; ++i)
free(lines[i]);
free(lines);
}
int
main()
{
struct student_info info;
char **lines;
lines = load_file("data.tx");
if (lines == NULL)
return -1;
info.courses = NULL;
info.size = 0;
for (size_t i = 0 ; lines[i] != NULL ; ++i)
{
char **courses;
courses = extract_courses_as_list(lines[i]);
if (courses == NULL)
continue;
concatenate_lists(&info, courses);
free_list(courses);
}
for (size_t i = 0 ; i < info.size ; ++i)
{
fprintf(stderr, "%s\n", info.courses[i]);
free(info.courses[i]);
}
free(info.courses);
free_list(lines);
return 0;
}
您会注意到我从未使用strdup()，原因是我们要复制的字符串的长度 始终已知。