Linux shell development

Hello everyone

could you please help me out with a project related to operating systems...
i plan to create our own shell in linux.. with a few functions
but dont know how to implement it...
could u please help!!

I know linux, and C and C++ prog
with a course in datastructures,ada

Use the search function up there, looks like building a new shell is a popular project these days !

You can read the source code of linux sys cmd , such as ls , pwd ......

It is my mini-shell code.

/* mshell.c */ 
#include <sys/types.h> 
#include <unistd.h> 
#include <sys/wait.h> 
#include <string.h> 
#include <errno.h> 
#include <stdio.h> 

void do_cd(char *argv[]); 
void execute_new(char *argv[]); 

main() 
{ 
   char *cmd=(void *)malloc(256*sizeof(char)); 
   char *cmd_arg[10]; 
   int cmdlen,i,j,tag; 

   do{ 
      /* init cmd */ 
      for(i=0;i<255;i++) cmd[i]='\0'; 

      printf("|*-=My Shell=-*| "); 
      fgets(cmd,256,stdin); 

      cmdlen=strlen(cmd); 
      cmdlen--; 
      cmd[cmdlen]='\0'; 

      for(i=0;i<10;i++) cmd_arg[i]=NULL; 
      i=0; j=0; tag=0; 
      while(i<cmdlen && j<10){ 
         if(cmd[i]==' '){ 
            cmd[i]='\0'; 
            tag=0; 
         }else{ 
            if(tag==0) 
               cmd_arg[j++]=cmd+i; 
            tag=1; 
         } 
         i++; 
      } 
       
      if(j>=10 && i<cmdlen){ 
         printf("TOO MANY ARGUMENTS\n"); 
         continue; 
      } 
       
      /* cmd quit: exit Mini Shell */ 
      if(strcmp(cmd_arg[0],"quit")==0) 
         break; 

      /* cmd cd */ 
      if(strcmp(cmd_arg[0],"cd")==0){ 
         do_cd(cmd_arg); 
         continue; 
      } 
       
      /* other cmd */ 
      execute_new(cmd_arg); 
   }while(1); 
} 

/* cd cmd */ 
void do_cd(char *argv[]) 
{ 
   if(argv[1]!=NULL){ 
      if(chdir(argv[1])<0) 
         switch(errno){ 
         case ENOENT: 
            printf("DIRECTORY NOT FOUND\n"); 
            break; 
         case ENOTDIR: 
            printf("NOT A DIRECTORY NAME\n"); 
            break; 
         case EACCES: 
            printf("YOU DO NOT HAVE RIGHT TO ACCESS\n"); 
            break; 
         default: 
            printf("SOME ERROR HAPPENED IN CHDIR\n"); 
         } 
   } 

} 

/* other cmd */ 
void execute_new(char *argv[]) 
{ 
   pid_t pid; 

   pid=fork(); 
   if(pid<0){ 
      printf("SOME ERROR HAPPENED IN FORK\n"); 
      exit(2); 
   }else if(pid==0){ 
      if(execvp(argv[0],argv)<0) 
         switch(errno){ 
         case ENOENT: 
               printf("COMMAND OR FILENAME NOT FOUND\n"); 
               break; 
            case EACCES: 
               printf("YOU DO NOT HAVE RIGHT TO ACCESS\n"); 
               break; 
                           default: 
                                   printf("SOME ERROR HAPPENED IN EXEC\n"); 
         } 
         exit(3); 
      }else 
         wait(NULL); 
}