쉘 프로그래밍 의문점 질문 드립니다..

#include <string.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#define MAX_CMD_ARG 10
 
const char *prompt = "myshell> ";
char* cmdvector[MAX_CMD_ARG];
char  cmdline[BUFSIZ];
 
void fatal(char *str)
{
	perror(str);
	exit(1);
}
 
void command_cd(char* path)     /command cd
{
	chdir(path);
}
 
int makelist(char *s, const char *delimiters, char** list, int MAX_LIST)
{	
  	int i = 0;
  	int numtokens = 0;
  	char *snew = NULL;
 
  	if((s == NULL) || (delimiters == NULL)) 
	{
		return -1;
	}
 
  	snew = s + strspn(s, delimiters);	/* delimitersžŠ skip */
  	if((list[numtokens] = strtok(snew, delimiters)) == NULL)
	{
    		return numtokens;
	}
 
  	numtokens = 1;
 
  	while(1)
	{
     		if((list[numtokens] = strtok(NULL, delimiters)) == NULL)
		{
			break;
		}
     		if(numtokens == (MAX_LIST - 1)) 
		{
			return -1;
		}
     		numtokens++;
  	}
  	return numtokens;
}
 
int main(int argc, char**argv)
{
  	int i=0;
  	pid_t pid;
  	while (1) 
	{      
  		fputs(prompt, stdout);
		fgets(cmdline, BUFSIZ, stdin);
		cmdline[ strlen(cmdline) -1] ='\0';
 
		i = makelist(cmdline, " \t", cmdvector, MAX_CMD_ARG);
 
		if(!strcmp(cmdline, "exit"))
		{
			exit(1);
		}
 
		if(!strcmp(cmdline, "cd"))      //command cd
		{
			command_cd(cmdvector[1]);
			continue;
		}
 
		switch(pid = fork())
		{
		case 0:
			makelist(cmdline, " \t", cmdvector, MAX_CMD_ARG);
			execvp(cmdvector[0], cmdvector);
			fatal("main()");
		case -1:
  			fatal("main()");
		default:
			wait(NULL);
		}
  	}
  	return 0;
}