编程实现linux下的shell

/*************************************************************************
    > File Name: Kris_shell.c
    > Author: KrisChou
    > Mail:zhoujx0219@163.com
    > Created Time: Thu 21 Aug 2014 04:31:55 PM CST
 ************************************************************************/

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

#define PROMPT ">>"
#define ARG_CNT 32

void command_to_arglist(char** arglist,char *cmd_line);

int main(int argc, char *argv[])
{
    char cmd_line[1024];
    char *arglist[ARG_CNT];
    while(memset(cmd_line,0,1024), printf("%s",PROMPT), fgets(cmd_line,1024,stdin))
    {
        if(cmd_line[0] != '\n')
        {
            cmd_line[strlen(cmd_line) - 1] = '\0'; //将读进来的换行符变成'\0'
            command_to_arglist(arglist,cmd_line);
            if(fork() > 0)
            {
                wait(NULL);
            }else
            {
                execvp(arglist[0],arglist);
                exit(0);
            }
        }
    }
    return 0;
}

static int my_isspace(char c)
{
    if(c == ' '|| c == '\n' || c == '\t' || c =='\v')
        return 1;
    else
        return 0;
}

static void command_to_arglist(char** arglist,char *cmd_line)
{
    int cnt = 0;
    int bg,end;
    bg = 0;
    while(cmd_line[bg] != '\0')
    {
        while(my_isspace(cmd_line[bg]))
        {
            bg++;
        }
        if(cmd_line[bg] == '\0')
        {
            break;
        }
        end = bg;
        while(cmd_line[end] != '\0' && !my_isspace(cmd_line[end]))
        {
            end++;
        }
        arglist[cnt] = (char*)calloc(1, (end-bg+1));
        strncpy(arglist[cnt],cmd_line+bg,(end-bg));
        cnt++;
        bg = end;
    }
    arglist[cnt] = NULL;

}