轻量级命令解释器

1.shell :命令解释器--外置命令

知识点：*命令有三类：外置命令、内置命令（cd）、别名

*getcwd()获得当前工作目录

chdir()改变当前工作路径

2.封装函数

1.输出命令提示

2.获取终端用户输入命令

3.解析用户命令

4.执行用户命令

5.退出当前exit

二、代码

.h

#ifndef __TERMINAL_H__
#define __TERMINAL_H__

#define CMD_MAX_LEN 512
#define CMD_MAX_CNT 10

extern void show_usr_cmd_line();
extern int get_usr_cmd(char *buff, int max_len);
extern int parse_usr_cmd(char *cmd_buff, char *arg[]);
extern void exec_usr_cmd(char *arg[], int cmd_cnt);

#endif

.c

#include "terminal.h"
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <sys/wait.h>

void show_usr_cmd_line()
{
	char buff[512] = {0};
	char path[128] = {0};

	getcwd(path, sizeof(path));
	sprintf(buff, "XXX@ubuntu:%s$ ", path);
	printf("%s", buff);

	return;
}

int get_usr_cmd(char *buff, int max_len)
{
	fgets(buff, max_len, stdin);
	
	buff[strlen(buff) -1] = '\0';
//	printf("buff = %s\n", buff);
	
	return 0;
}

int parse_usr_cmd(char *cmd_buff, char *arg[])
{
	int i = 0;

	arg[i] = strtok(cmd_buff, " ");
	while (arg[i] != NULL)
	{
		i++;
		arg[i] = strtok(NULL, " ");
	}

	return i;
}


void exec_usr_cmd(char *arg[], int cmd_cnt)
{
	pid_t pid = fork();
	if (pid > 0)
	{
		wait(NULL);
	}
	else if (0 == pid)
	{
		execvp(arg[0], arg);
		printf("fail exec\n");
	}
	else
	{
		printf("fail fork\n");
	}
}

main.c

#include <stdio.h>
#include "terminal.h"
#include <string.h>

int main(int argc, const char *argv[])
{
	char cmd_buff[CMD_MAX_LEN] = {0};
	char *arg[CMD_MAX_CNT] = {NULL};
	int cmd_cnt = 0;
	
	while (1)
	{
		show_usr_cmd_line();
		get_usr_cmd(cmd_buff, CMD_MAX_LEN);
		cmd_cnt = parse_usr_cmd(cmd_buff, arg);
		if (!strcmp(arg[0], "exit"))
		{
			break;
		}
		else if (!strcmp(arg[0], "cd"))
		{
			//cd /
			chdir(arg[1]);
			continue;
		}
		exec_usr_cmd(arg, cmd_cnt);
	}

	return 0;
}

二、效果