myshell.c

应用UNIX的fork()等系统调用

/*       操作系统练习1： myshell.c  
           姓名： 杨富强
           学院：通信工程 
           学号：01051312 
          在Ubuntu7.10和cygwin下已经测试通过
*/ 

#include "myshell.h" 

int main (int argc, char *argv[])
{
    char buf [MAX_BUFFER], pwd [MAX_ARGS];    // line buffer
    char shell_path[MAX_ARGS]="shell=";
    char readme_path[MAX_ARGS]="readme_path=";
    char newpath[MAX_ARGS*1000];
     int len;  
   strcpy(newpath,getenv("PATH"));
   strcat(newpath,":");
     if(strcmp(argv[0],"./myshell")&&strcmp(argv[0],"myshell")) 
         {                 
              len=strlen(argv[0]);  
            while(len&&argv[0][len]!='/')   len-- ; 
            argv[0][len]='\0';           
           strcpy(pwd,argv[0]);    
           get_fullpath(pwd, argv[0]);  
             printf("%s\n",pwd);  
            }
   
       else  strcpy(pwd  ,getenv("PWD"));    
      strcat(newpath,pwd);   // strcat(newpath,getenv("PWD"));     
     setenv("PATH",newpath,1);// add the current working directory  in the "PATH" environment variable to search for the filename specified.
   
     strcat(shell_path,pwd);   //  strcat(shell_path, getenv("PWD"));
    strcat(shell_path,"/myshell");
    putenv( shell_path); //add the working directory  of myshell in the environment variables           
      strcat(readme_path, pwd);  //   strcat(readme_path, getenv("PWD"));//    
       strcat(readme_path,"/readme");         
      putenv(readme_path); //   add the filepath of the file "readme"  in the  environment variables, see function  my_help( ) ! 
      
    if(argc>1)  // 也许用户直接在终端输入  ./myshell a.bat  >c.txt 
	{
	   strcpy(buf,"myshell ");
	   int i;
	   for(i=1;i<argc;i++)
	   {
		   strcat(buf,argv[i]);
	       strcat(buf,"  ");
	   }
	   Execute(buf);// execute this command，  执行这个批处理命令
	}

	else  // 如果用户在终端输入 ./myshell
	{
	   my_clear( );
           fprintf(stderr, "Welcome Enter myshell!\nType \"help\" to see the help information.\n");          
	   my_shell(stdin,NULL,NULL);
	 }
    return 0 ; 
}    // end  function "main"