myshell.c

操作系统课程设计

/*Copyright:CaiShaowei@Computer Science College Of SCUT,2004(2),NO.200433100067**
 *************this program makes a "Shell" of Unix Operation System*************/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <dirent.h>
#include <string.h>
#include <sys/wait.h>

#define CD      1
#define ENVIRON 2
#define ECHO    3
#define HELP    4
#define JOBS    5
#define QUIT    6
#define PWD     7
#define RUN_PROCESS 8


#define order_max 100  //the max length of an order
#define echo_len  100  //the number of the strings can be in the "echo" command
#define echo_max  300  //the max length of every string of "echo" command
#define dir_max   100  //the max length of the path of directory or file

int input_order();
void cd();
void environ();
void echo();
void help();
void jobs();
void pwd();
void run_process();

static char order[order_max]; //order string got from the user(keyboard)
static char dir[dir_max];     //directory

int main()
{
	
	int choice = 0;//the choice that user input
	char hostname[50] ;//hostname of computer
	char user[50];//user name
	strcpy(hostname, getenv("HOSTNAME"));
	strcpy(user,getenv("USER"));
	strcpy(dir,getenv("PWD"));//get the pwd of the Operation System in the beginning.
	printf("[%s %s]# ",user,dir);
	while(1)
	{
		choice = input_order();
		switch(choice)
		{
			case CD:
				cd();
				break;
			case ENVIRON:
				environ();
				break;
			case ECHO:
				echo();
				break;
			case HELP:
				help();
				break;
			case JOBS:
				jobs();
				break;
			case QUIT:
				printf("Byebye!\n");
				return 0;
			case PWD:
				pwd();
				break;
			case RUN_PROCESS:
				run_process();
				break;
		}
		printf("[%s %s]# ",user,dir);
	}
	return 0;
}

int input_order()
{
	scanf("%s255",&order);
	if(strcmp(order,"cd")==0)
	{
		return CD;
	}
	else if(strcmp(order,"environ")==0)
	{
		return ENVIRON;
	}
	else if(strcmp(order,"echo")==0)
	{
		return ECHO;
	}
	else if(strcmp(order,"help")==0)
	{
		return HELP;
	}
	else if(strcmp(order,"jobs")==0)
	{
		return JOBS;
	}
	else if(strcmp(order,"pwd")==0)
	{
		return PWD;
	}
	else if(strcmp(order,"quit")==0||strcmp(order,"exit")==0
	                               ||strcmp(order,"bye")==0)
	{
		return QUIT;
	}
	else
	{
		return RUN_PROCESS;
	}
}

/***function:cd . to change the current directory.***/ 
void cd()
{
	scanf("%sdir_max",&dir);
	if(chdir(dir) == -1)//change the direction
	{
		perror("this is not a valid directory");
	      if(getcwd(dir,dir_max)==NULL)//if the input string is not a valid directory,rewrite "dir" as current 									directory
	      	{
	      	perror("wrong:");
	      	exit(1);
	      	}
	}
}

/****function:environ , to print the environment set in the Operation System.****/
void environ()
{
	printf("HOSTNAME=%s\n",getenv("HOSTNAME"));
	printf("TERM=%s\n",getenv("TERM"));
	printf("HISTSIZE=%s\n",getenv("HISTSIZE"));
	printf("WINDOWID=%s\n",getenv("WINDOWID"));
	printf("PWD=%s\n",getenv("PWD"));
	printf("MAIL=%s\n",getenv("MAIL"));
	printf("USER=%s\n",getenv("USER"));
	printf("HOME=%s\n",getenv("HOME"));
	printf("PATH=%s\n",getenv("PATH"));
}

/*** functio:echo. to print string the user input.***/ 
void echo()
{
	char echo_string[echo_len][echo_max];//used to store the strings of the "echo" command
	int echo_num = 0;
	while(getchar()!='\n')   //read ' ' or '\n' from keyboard,stop inputing echo_string when meets '\n'
	{
		scanf("%s300",&echo_string[echo_num]);
		echo_num++;
	}
	int i;
	for(i=0;i<echo_num;i++)
	{
		printf("%s ",echo_string[i]);
	}
	
	printf("\n");
}

/***function:help. to print the help information of the program.***/
void help()
{
	printf("  *****shell by ShaoweiCai@2004(2),SCUT  version 1.0****\n");
	printf("**********************************************************\n");
	printf("cd [dir]     :  Change the current direction to dir.\n");
	printf("echo [string]:  Display a line of text,follow by a new line.\n");
	printf("environ      :  Print the environment settings of the Operation System.\n");
	printf("exit         :  Cause the shell to exit.\n");
	printf("help         :  Display helpful information about commands of the shell program.\n");
	printf("jobs         :  This is a jobs order.\n");
	printf("quit         :  Cause the shell to exit.\n");
	printf("bye          :  Cause the shell to exit.\n");
	printf("[path]       :  path can be the path of a command or a excute file,cause to                     excute the command or the excute file,'./' means the current                    directory.\n");
	
}

/***function:jobs ***/
void jobs()
{
	printf("this is jobs order.\n");
}

/***function: pwd. to display the current path.***/
void pwd()
{
	char name[dir_max];
	if(getcwd(name,dir_max)==NULL)
	{
		printf("error:getcwd\n");
		exit(1);
	}
	printf("%s\n",name);
}

/***function: run_process.to fork a process of a excuting  file***/
void run_process()
{
	pid_t childpid;
	
	childpid = fork();//fork a child process
	if(childpid==-1)
	{
		perror("Failed to fork");
		return;
	}
	if(childpid==0)
	{
		if(order[0]=='.'&&order[1]=='/')//the excuting file in current directory
		{
			int proname_len = strlen(order)-1;
			int i;
			char process_name[proname_len];
			for(i = 0;i<proname_len;i++)
			{
				process_name[i] = order[i+1];
			}
			if(getcwd(order,order_max)==NULL)//get the current directory(the path of the excuting file
			{
				printf("error:getcwd\n");
				exit(1);
			}
			strcat(order,process_name);//get the exact name of the cxcuting file,and write it into the "order"   									 array.
		}
		execl(order,NULL);//excute the child process
		printf("Invalid input:it is not a executive file");
		return;
	}
	if(childpid!=wait(NULL))//the parent wait untill the child process ends.
	{
		perror("parent failed to wait due to signal or error");
	}
}