Unexpected behavior with my token function - c

Question

I am trying to write a simple Shell in C. Eventually, I will implement forking of processes and piping etc. But, right now, I'm just trying to get all the logic worked out.
I have a partially working shell: When I type exit it exits... however, my token function doesn't seem to be working right.
What am I doing wrong here? I'm not sure why its seg-faulting.
Token prints out once in the while loop and then it seg-faults and crashes.
#include <stdio.h>
#include <sys/wait.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#define MAX_BUF_SZ 1024
void checkForPipe(char *string, bool *pipe_bool);
void checkForRedirect(char *string, bool *redirect_bool);
void tokenizeInput(char *string, bool pipe, bool redirect);
int main()
{
char *ptr;
bool is_pipe = 0;
bool is_redirect_out = 0;
bool is_exit = 0;
ptr = (char*)malloc(MAX_BUF_SZ);
while(!is_exit)
{
// Diplay prompt
char cur_dir[MAX_BUF_SZ];
getcwd(cur_dir, MAX_BUF_SZ);
printf("SHELL:%s$ ", cur_dir);
fgets(ptr, MAX_BUF_SZ, stdin);
checkForPipe(ptr, &is_pipe);
checkForRedirect(ptr, &is_redirect_out);
printf("pipe flag = %d\n", is_pipe);
printf("redirect flag = %d\n", is_redirect_out);
if(strcmp(ptr, "exit\n") == 0)
{
is_exit = 1;
}
tokenizeInput(ptr, is_pipe, is_redirect_out);
}
return 0;
}
void checkForPipe(char *string, bool *pipe_bool)
{
char *check_for_pipes;
char *clean_compare;
check_for_pipes = (char*)malloc(MAX_BUF_SZ);
clean_compare = (char*)malloc(MAX_BUF_SZ);
strcpy(check_for_pipes, string);
strcpy(clean_compare, string);
char * token = strtok(check_for_pipes, "|");
if(strcmp(token, clean_compare) == 0)
{
free(clean_compare);
free(check_for_pipes);
}
else
{
*pipe_bool = 1;
free(clean_compare);
free(check_for_pipes);
}
}
void checkForRedirect(char *string, bool *redirect_bool)
{
char *check_for_redirects;
char *clean_compare;
check_for_redirects = (char*)malloc(MAX_BUF_SZ);
clean_compare = (char*)malloc(MAX_BUF_SZ);
strcpy(check_for_redirects, string);
strcpy(clean_compare, string);
char * token = strtok(check_for_redirects, ">");
if(strcmp(token, clean_compare) == 0)
{
free(clean_compare);
free(check_for_redirects);
}
else
{
*redirect_bool = 1;
free(clean_compare);
free(check_for_redirects);
}
}
void tokenizeInput(char *string, bool pipe, bool redirect)
{
char *copy_string;
copy_string = (char*)malloc(MAX_BUF_SZ);
strcpy(copy_string, string);
if(pipe == 0 && redirect == 0)
{
char **args = {NULL};
char *token = strtok(copy_string, " ");
int i = 0;
printf("%s\n", token);
while(token != NULL)
{
args[i] = token;
strtok(NULL, " ");
printf("%s\n", token);
i++;
}
}
/* printf("%s\n%s\n%s\n", args[0], args[1], args[2]); */
}

Answer 1

The problem is on args[i]
I modified your code as follows:
Supposing you have a pre-known number of token which is MAX_BUF_SZ.
You allocate MAX_BUF_SZ pointers of type char*
char **args = malloc(MAX_BUF_SZ * sizeof(char *));
and in the loop, you still have to allocate each pointer char* before using it:
while(token != NULL)
{
args[i] = (char *)malloc(strlen(token)+1);
printf("%s\n", token);
args[i] = token;
token = strtok(NULL, " ");
i++;
}
The whole functions is like this:
void tokenizeInput(char *string, bool pipe, bool redirect)
{
char *copy_string;
copy_string = (char*)malloc(MAX_BUF_SZ);
strcpy(copy_string, string);
// suppose we would have MAX_BUF_SZ tokens
char **args = malloc(MAX_BUF_SZ * sizeof(char *));
if(pipe == 0 && redirect == 0)
{
char *token = strtok(copy_string, " ");
int i = 0;
//printf("token %s\n", token);
while(token != NULL)
{
args[i] = (char *)malloc(strlen(token)+1);
printf("%s\n", token);
args[i] = token;
token = strtok(NULL, " ");
i++;
}
}
/* printf("%s\n%s\n%s\n", args[0], args[1], args[2]); */
}
Here is my example running :
SHELL:D:\Users\T0180694\Documents\Mes Outils Personnels\PAN\PAN_folder$ test is essai of you and me
pipe flag = 0
redirect flag = 0
test
is
essai
of
you
and
me