Bantuan dengan implementasi shell linux sederhana

Saya menerapkan versi sederhana dari shell linux di c.

Saya telah berhasil menulis parser, tetapi saya mengalami kesulitan dalam melakukan proses anak. Namun, menurut saya masalahnya adalah karena array, pointer dan semacamnya, karena baru saja memulai C dengan proyek ini dan saya masih belum terlalu paham dengan mereka.

Saya mendapatkan kesalahan segmentasi dan tidak tahu dari mana. Bantuan apa pun sangat dihargai.

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/wait.h>
#include <sys/types.h>

#define MAX_COMMAND_LENGTH 250
#define MAX_ARG_LENGTH 250

typedef enum {false, true} bool;

typedef struct {
    char **arg;     
    char *infile;   
    char *outfile;  
    int background; 
} Command_Info;

int parse_cmd(char *cmd_line, Command_Info *cmd_info)
{
    char *arg;
    char *args[MAX_ARG_LENGTH]; 

    int i = 0;
    arg = strtok(cmd_line, " ");
    while (arg != NULL) {
        args[i] = arg;
        arg = strtok(NULL, " ");
        i++;
    }

    int num_elems = i;
    if (num_elems == 0)
        return -1;

    cmd_info->infile = NULL;
    cmd_info->outfile = NULL;
    cmd_info->background = 0;

    int iarg = 0;
    for (i = 0; i < num_elems-1; i++)
    {                   
        if (!strcmp(args[i], "<"))
        {
            if (args[i+1] != NULL)
                cmd_info->infile = args[++i];
            else
                return -1;                      
        }

        else if (!strcmp(args[i], ">"))
        {
            if (args[i+1] != NULL)
                cmd_info->outfile = args[++i];
            else 
                return -1;                          
        }

        else
            cmd_info->arg[iarg++] = args[i];
    }

    if (!strcmp(args[i], "&"))
        cmd_info->background = true;
    else
        cmd_info->arg[iarg++] = args[i];

    cmd_info->arg[iarg] = NULL; 

    return 0;   
}


void print_cmd(Command_Info *cmd_info)
{
    int i;  
    for (i = 0; cmd_info->arg[i] != NULL; i++)
        printf("arg[%d]=\"%s\"\n", i, cmd_info->arg[i]);
    printf("arg[%d]=\"%s\"\n", i, cmd_info->arg[i]);    
    printf("infile=\"%s\"\n", cmd_info->infile);
    printf("outfile=\"%s\"\n", cmd_info->outfile);
    printf("background=\"%d\"\n", cmd_info->background);
}

void get_cmd(char* str)
{
    fgets(str, MAX_COMMAND_LENGTH, stdin);
    str[strlen(str)-1] = '\0'; //apaga o '\n' do fim
}

pid_t exec_simple(Command_Info *cmd_info)

{
    pid_t pid = fork();


    if (pid < 0)
    {
        perror("Fork Error");
        return -1;
    }



    if (pid == 0)

    {
        execvp(cmd_info->arg[0], cmd_info->arg);

        perror(cmd_info->arg[0]);
        exit(1);
    }


    return pid;

}

int main(int argc, char* argv[])
{

    while (true)
    {
        char cmd_line[MAX_COMMAND_LENGTH];
        Command_Info cmd_info;

        printf(">>> ");

        get_cmd(cmd_line);

        if ( (parse_cmd(cmd_line, &cmd_info) == -1) )   
            return -1;

        parse_cmd(cmd_line, &cmd_info);



        if (!strcmp(cmd_info.arg[0], "exit"))
            exit(0);

        pid_t pid = exec_simple(&cmd_info);

        waitpid(pid, NULL, 0);  
    }

    return 0;
} 

Terima kasih.