/*BY Dai Qieyun *   Chen Xinwei *   Dai Wei*/#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <errno.h>#include <sys/wait.h>#include <stdlib.h>#include <string.h>

extern char **getline();

main() {  int i;
  char **args;  int pid;  int stat_val;  int isRedirect;  int isPipe;  int isBack;  int position;   printf("Welcome to MyShell ^_^\n");

  while(1) {        isRedirect=0;    isPipe=0;    position=0;
    printf("MyShell>>");    args = getline();    for(i = 0; args[i] != NULL; i++){    //testing whether the command is redirection or pipe      if(!strcmp(args[i],"<")||!strcmp(args[i],">"))	{	  isRedirect=1;	  position=i;	}      if(!strcmp(args[i],"|")){	  isPipe=1;	  position=i;	}    }
        if(args[0]==NULL); //empty command    else if(!strcmp(args[i-1],"&")){//background execution      args[i-1] = NULL;      pid=fork();//bulid a runback process,and don't eliminate the parent process      if(pid==-1) {          perror("Failed to fork");         return 1;      }      if(pid == 0){         if(setsid() == -1)            perror("Child faild to become a session leader");         else{             execvp(args[0],args);            printf("Command not found in PATH\n");            exit(0);         }         return 1;      }    }    else if(isPipe){  //pipe	pid_t child,gChild;	int file_pipes[2];		char **command;        command=&args[position+1];	args[position]=NULL;        child=fork();        switch(child){            case -1:              perror("Fork Failed\n");              exit(-1);            case 0:              if(!pipe(file_pipes)){                  gChild=fork();                  switch(gChild){                     case -1:                        fprintf(stderr,"Fork Failed\n");                        exit(-1);                     case 0:           //the grandchild process,writing to the pipe                                                close(1);                        dup2(file_pipes[1],1);                        close(file_pipes[1]);                        close(file_pipes[0]);                        execvp(args[0],args);                        printf("Command not found in PATH\n");                        exit(0);                         default:         //the child process, reading from the pipe                                                close(0);                        dup(file_pipes[0]);                        close(file_pipes[0]);                        close(file_pipes[1]);                        execvp(command[0],command);                        printf("Command not found in PATH\n");                        exit(0);                                         }              }                default:                   waitpid(child,&stat_val,0);                   if(!WIFEXITED(stat_val))                        printf("Child terminated abnormally\n");         }                              }    else if(!strcmp(args[0],"exit")) //the exit command        exit(0);        else if(!strcmp(args[0],"add")){ //the add command        pid=fork();                switch(pid){           int i;           int result;                   case -1:              perror("Fork Failed\n");              exit(-1);                      case 0:              if(isRedirect){                 char *fileName;		 fileName=args[position+1];		 args[position]=NULL;		 if(!freopen(fileName,"w",stdout)){ //Redirect the add result to file		    fprintf(stderr,"could not redirect stdout to file %s\n",fileName);		    exit(2);	         }              }                  result=add(args);              for(i=1;args[i+1]!=NULL;i++)                 printf("%s+",args[i]);              printf("%s=%d\n",args[i],result);              exit(0);                      default:              wait(&stat_val);              if(!WIFEXITED(stat_val))                  printf("Error:child terminated abnormally\n");          }   }   else if(!strcmp(args[0],"args")){ //the args command       pid=fork();       switch(pid){         case -1:            perror("Fork Failed\n");            exit(-1);         case 0:            if(isRedirect){               char *fileName;	       fileName=args[position+1];	       args[position]=NULL;		 if(!freopen(fileName,"w",stdout)){ //redirect args result to file		    fprintf(stderr,"could not redirect stdout to file %s\n",fileName);		    exit(2);	      }            }                arg(args);            exit(0);         default:            wait(&stat_val);            if(!WIFEXITED(stat_val))                printf("Error:child terminated abnormally\n");      }   }   else if(!strcmp(args[0],"search")){
        printf("%d found\n",search(args));
   }
   else {   //the rest of the cases        pid=fork();        switch(pid){            case -1:              perror("Fork Failed\n");              exit(-1);            case 0:              if(isRedirect){  //redirection                 char *fileName;		 fileName=args[position+1];		 if(*args[position]=='>'){		    args[position]=NULL;		    if(!freopen(fileName,"w",stdout)){ //writing to file, closing standard out			fprintf(stderr,"could not redirect stdout to file %s\n",fileName);			exit(2);		    }		    execvp(args[0],args);                    fprintf(stderr,"Command not found in PATH\n");                    exit(0);	         }    	         else{		    args[position]=NULL;		    if(!freopen(fileName,"r",stdin)){ //reading rom file, closing standard in		       fprintf(stderr,"could not redirect stdin to file %s\n",fileName);		       exit(2);		    }		    execvp(args[0],args);                    printf("Command not found in PATH\n");                    exit(0);		}              }              else{                           execvp(args[0],args);                   printf("Command not found in PATH\n");                   exit(0);              }            default:              wait(&stat_val);              if(!WIFEXITED(stat_val))                  printf("Error:child terminated abnormally\n");    
        }     }
   }}int add(char**args){   int sum=0;    int i;   for(i=1;args[i]!=NULL;i++){      if(args[i][0]=='0'&&args[i][1]!='\0'&&(args[i][1]=='x'||args[i][1]=='X'))         sum+=hex(args[i]);      else         sum+=dec(args[i]);   }   return sum;}int dec(char* str){ //converting string notation of dec number to decimal int   int num=0;   int i;   for(i=0;str[i]!='\0';i++){     int digit=str[i]-'0';       if(digit<0||digit>9){         printf("Wrong with your input\n");         exit(0);       }      num=10*num+digit;   }   return num;}int getNumber(char a){ //converting char to number   if('0'<=a&&a<='9')     return a-'0';   else if ('a'<=a&&a<='f')     return 10+a-'a';   else if('A'<=a&&a<='F')     return 10+a-'A';   else{     printf("Wrong with your input\n");     exit(0);  }} int hex(char* str){ //converting string notation of hex number to decimal int   int num=0;   int i;   for(i=2;str[i]!='\0';i++){     int digit=getNumber(str[i]);       num=16*num+digit;   }   return num;}arg(char** args){   char* result;   int i;   if(args[1]==NULL){     printf("args=0");     return;   }   for(i=1;args[i]!=NULL;i++);   printf("argc=%d,args=",i-1);   for(i=1;args[i+1]!=NULL;i++)     printf("%s,",args[i]);   printf("%s\n",args[i]);}int search(char ** args)  //search the file you give , count the times of the string you have given
{
    char*str=args[1];
    char*filename=args[2];
    printf("search \"%s\" in file %s\n",str,filename);
    int count=0;
    int c;
    int i=0;
    int len=strlen(str);
    FILE *fp;
    fp=fopen(filename,"r");

    while((c=fgetc(fp))!=EOF)
    {
        if(c==str[i])
        {
            if(++i==len)
            count++;
        }
        else
        {
            i=0;
        }
        }
    fclose(fp);
    return count;
}