Fill a struct containing char** array as a member, C - c

Question

...currently am practicing to fill a struct that contains an array(char array to store multiple elements). The scenario am trying to implement is as follows:
The general task is (to store student information, name as string and courses taken by the student as a list or char**)
student information is first loaded from file!(myfile.txt)
tokenize/parse student information and load to struct
The file that contains my student information is:
myfile.txt (each line contains student name and list of courses) delimited by ":"
Austin Barbra:Biology,chemistry,maths,music
Romio Chandra:Mechanics,IT,Geology,music,Astronomy
.
.
My main.c is:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define path "myfile.txt"
typedef struct student_info
{
char *studt_name;
char *cources_as_string;
char **cources_as_list;
}std_info ;
std_info *myinfo; //a global var that will conatain student info
int student_count = 0,cource_count=0;
void load_file()
{
int i,yu,index=0;
char *line =NULL,* token = NULL;
size_t len=0;
FILE *fp;
fp =fopen(path,"r");
if(fp==NULL)
{
perror("FILE OPEN ERROR[IN load_file]: ");
return;
}
if (( myinfo = (struct student_info *) malloc( 2 * sizeof(myinfo) ) ) == NULL)//malloc for 2 students
puts ("malloc fail");
while (getline(&line, &len, fp) != -1 )
{
strtok(line,"\n");
char *token;
token = strtok(line,":");
myinfo[index].studt_name=(char * ) malloc(200 * sizeof(char ) );
strcpy(myinfo[index].studt_name,token);
token = strtok(NULL, ":");
myinfo[index].cources_as_string=(char * ) malloc(200 * sizeof(char ) );
strcpy(myinfo[index].cources_as_string,token);
index++;
}
student_count = index;
fclose(fp);
}
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,",");
cource_list[0]= token;
while (token != NULL)
{
cource_list[index]= token;
token = strtok (NULL, ",");
index++;
}
cource_count = index;
return cource_list;
}
int main()
{
int i,j;
load_file();
for(i=0;i<student_count;i++)
{
printf("============================\n");
printf("NAME: %s >>COURCE_string: %s\n",myinfo[i].studt_name,myinfo[i].cources_as_string);
char ip_list[200];
char** std_cource_list = return_cource_list(myinfo[i].cources_as_string);
for(j=0;j<cource_count;j++)
{
printf("\tCOURCE_list[%d]: %s\n",j,std_cource_list[j]);
//segmentation fault exists here, to copy "std_cource_list[j]" to my struct...(need help here).
strcpy(myinfo[i].cources_as_list[j],std_cource_list[j]);
}
}
}
The problem am facing is to fill the "char **cources_as_list;" member of the struct. Am getting a seg_fault from the inner for loop(iterating on j). Do i miss something in my code?

Answer 1

I fixed it quick so that it doesn't crash and output is correct, it can be better (there are leaks we can fix) but it actually prints your stuff now.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define path "myfile.txt"
typedef struct student_info {
char *studt_name;
char *cources_as_string;
char **cources_as_list;
} std_info;
std_info *myinfo; //a global var that will conatain student info
int student_count = 0, cource_count = 0;
void load_file() {
int i, yu, index = 0;
char *line = NULL, *token = NULL;
size_t len = 0;
FILE *fp;
fp = fopen(path, "r");
if (fp == NULL) {
perror("FILE OPEN ERROR[IN load_file]: ");
return;
}
if ((myinfo = (struct student_info *) malloc(2 * sizeof(*myinfo))) == NULL)//malloc for 2 students
puts("malloc fail");
while (getline(&line, &len, fp) != -1) {
strtok(line, "\n");
char *token;
token = strtok(line, ":");
myinfo[index].studt_name = malloc(200 * sizeof(char));
strcpy(myinfo[index].studt_name, token);
token = strtok(NULL, ":");
myinfo[index].cources_as_string = malloc(200 * sizeof(char));
strcpy(myinfo[index].cources_as_string, token);
index++;
}
student_count = index;
//fclose(fp);
}
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, ",");
cource_list[0] = token;
while (token != NULL) {
cource_list[index] = strdup(token);
token = strtok(NULL, ",");
index++;
}
cource_count = index;
return cource_list;
}
/* returns an array of char*, all of which NULL */
char **alloc_argv(unsigned rows) {
char **matrix = malloc(rows * sizeof(char *));
if (!matrix) abort();
for (unsigned row = 0; row < rows; row++) {
matrix[row] = malloc(rows * sizeof(char *));
matrix[row] = "\0";
if (!matrix[row]) abort();
}
return matrix;
}
int main() {
int i, j;
load_file();
for (i = 0; i < student_count; i++) {
printf("============================\n");
printf("NAME: %s >>COURCE_string: %s\n", myinfo[i].studt_name, myinfo[i].cources_as_string);
char ip_list[200];
char **std_cource_list = return_cource_list(myinfo[i].cources_as_string);
for (j = 0; j < cource_count; j++) {
printf("\tCOURCE_list[%d]: %s\n", j, std_cource_list[j]);
//segmentation fault exists here, to copy "std_cource_list[j]" to my struct...(need help here).
myinfo[i].cources_as_list = alloc_argv(100);
myinfo[i].cources_as_list[j] = malloc(sizeof(char **));
strcpy(myinfo[i].cources_as_list[j], std_cource_list[j]);
}
}
}
Output
============================
NAME: Austin Barbra >>COURCE_string: Biology,chemistry,maths,music
COURCE_list[0]: Biology
COURCE_list[1]: chemistry
COURCE_list[2]: maths
COURCE_list[3]: music
============================
NAME: Romio Chandra >>COURCE_string: Mechanics,IT,Geology,music,Astronomy
COURCE_list[0]: Mechanics
COURCE_list[1]: IT
COURCE_list[2]: Geology
COURCE_list[3]: music
COURCE_list[4]: Astronomy
Process finished with exit code 0