.

#include <string.h> 
#include <unistd.h> 
#include <stdio.h> 
#include <stdlib.h> 
#include <wait.h>
#define MAX_CMD_ARG 10 
 
const char *prompt = "(sp@resl$) ";
char* cmdvector[MAX_CMD_ARG];
char  cmdline[BUFSIZ];
 
void fatal(char *str)
{
	perror(str);
	exit(1);
}
 
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);
	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';
		if (strcmp(argv[0], "exit") == 0 || strcmp(argv[0], "quit") == 0)
		{
			printf("EXIT\n");
			exit(0);
		}
		else
		{
			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;
}