shell.c

我编写的linex 下的一个子shell

/* Practise 2    shell */
/* lichangshun */
#include<stdio.h>
#include<stdlib.h>
#include<error.h>
#include<sys/wait.h>

#define MAXLINE 200
#define MAXARG 20
#define false  0
#define true 1
#define bool int

extern char **environ;
int T_and=0;   // whether have & 
int T_lt=0;    // <
int T_rt=0;    // >
//char * inname;
//char *outname; //use for redirect

bool getargs(int *argcp,char *argv[],int max,bool *eofp){
  static char cmd[MAXLINE];
  char *cmdp;
  int i=0;
  int len=0;

  *eofp=false;
  
  if(fgets(cmd,sizeof(cmd),stdin)==NULL){
    *eofp=true;
    return false; 
  } 
  if(strchr(cmd,'\n')==NULL){
    /*eat up rest of line */
    while(1){
      switch(getchar()){
        case '\n': break;
        default: continue;
      }//switch
     break;
    }//while
    printf("Line is too  long!\n");
    return false;
  }//if
  /*find whether have & or | or < or >*/
   len=strlen(cmd);
   //printf("len=%d shiyan:%s",len,cmd);

   if(cmd[len-2]=='&'){
      T_and=1;
      cmd[len-2]='\0'; 
   }
   //printf("haha%s",cmd);

/*
   for(i=0;i<len;i++){
     if(cmd[i]=='<'){
       T_lt=1; 
     }
     if(cmd[i]=='>'){
       T_rt=1;
       ///////////////////
  //     cmd[i]='\0';
     }

   }

*/

/////////////////////
  cmdp=cmd;
  for(i=0;i<max;i++){
    if((argv[i]=(char *)strtok(cmdp," \t\n"))==NULL)
      break;
    cmdp=NULL;    /*tell strtok to keep going*/
  }
  if(i>=max){
    printf("Too many args -- commands ignored!");
    return false;
  }
  *argcp=i;
  return true;
/*  */
}//getargs

void set(int argc,char *argv[]){
  int i=0;
  
  if(argc!=1) 
    printf("Extra args!\n");
  else 
    for(i=0;environ[i]!=NULL;i++)
      printf("%s\n",environ[i]);
}

int main(void){
  void execute(int ,char *[]);
  char *argv[MAXARG];
  int argc=0;
  int eof=0;
  int len=0;
  int i=0;
  int counter=0;
  char paths[80];
  char *temp;
  while(1){
  eof=0;
  //get environment and print and you should change it if nessary!!!
  getcwd(paths,80);   
  //  paths[strlen(paths)]='\0';
  argv[0]="";
  printf("[%s]#",paths);
  //
   if(getargs(&argc,argv,MAXARG,&eof)&&argc>0){
   //  
     if(strcmp(argv[0],"exit")==0){
        //eof=1; // 
        exit(0);
       
      }
     else if(strcmp(argv[0],"lichangshun")==0){
       printf("lichangshun is my owner!\n");
     }
     else if(!strcmp(argv[0],"cd")){ //command_cd  
        if(argv[1]!=NULL)// if cd char*
        {//if(!access(,0)){}
         // strcpy(temp,argv[1]);
          getcwd(paths,80);
          strcat(paths,"/");
          strcat(paths,temp);
         // printf("@@%s_",argv[1]);         
          if(!access(paths,0)){
            chdir(paths);
            //printf("1%s",paths);
          } 
          else if(!access(argv[1],0)){
          //  printf("%s_",argv[1]);
            chdir(argv[1]);
            getcwd(paths,80);
          //  printf("d%s",paths);
          }
          else printf("bash: cannot find the file or directory!\n");
          
        }
        else if(argv[1]==NULL){
         //return to higher dir
         getcwd( paths,80);
         len=strlen(paths);
         for(counter=0;counter<len;counter++){
           if(paths[len-counter]=='/') {
              paths[len-counter]='\0';  
              break;
            }
         }
        // printf("%s\n",paths);
         chdir(paths);
        } 

     }
     else if(strcmp(argv[0],"set")==0)
       set(argc,argv);
     else{
        //  printf("_%d_%s_%s_%s_%s_%s__",argc,argv[0],argv[1],argv[2],argv[3],argv[4]);
        execute(argc,argv);
      //  printf("__ok__\n"); 
     }
   }//if
    
   if(eof)  exit(EXIT_SUCCESS);
  }//while(1)   
}//main

 void execute(int argc,char *argv[]){
  int pid;
  int status;
  int i,j;
   
 // printf("*%d*%s*%s**\n",argc,argv[0],argv[1]);
  pid=fork();
  //printf("..%d..\n",pid);           
  switch (pid){
    //printf("...%d..%s",pid,argv[0]);
   case -1: 
     // 
     printf("wrong 1 !~\n");
   case 0:
      j=execvp(argv[0],argv);
      if(j==-1){
         printf("Wrong command!\n");
         exit(1);  //if wrong exit(1)  
      }
     printf("..ttttt..\n");
    // break;  
   default:
     //
     if(T_and==0){
       i=waitpid(pid,&status,0);
     }
     else if(T_and==1){
       return;
     } 

    // display_status(pid,status);     
    // break;
     
  } 
  return;

}