XV6-----Shell

This is the first programming job of the operating system principle course, which complements the functionality of the shell.

The main implementation of the basic three types of commands

• Executable program Commands
• REDIRECT Command
• Pipeline command

The implementation of the "base class" (Forgive me for using this word) is a struct cmd this struct is a member that is used to record the type of command.

Three classes, "means executable program ' | ' represents the pipeline command, ' < ' and ' > ' represent the redirection type.

Each type inherits the base class, and derives the corresponding three classes of struct

struct EXECCMD

struct REDIRCMD

struct PIPECMD

void Runcmd (struct cmd * cmd);

This function is the core of the real driver invocation implementation shell. is responsible for invoking the system interface function EXECV (), open (), close (), DUP (), pipe () and so on a series of functions to accomplish our established goal.

The job is to complete this function.

This is a recursive function!

Here's the code from GitHub that extracts only the Runcmd function

1 void2Runcmd (structCMD *cmd)3 {4   intp[2];//used for pipe line in shell5   intR//return value6   structExecCmd *Ecmd;7   structPipecmd *Pcmd;8   structRedircmd *Rcmd;9 Ten   if(cmd = =0) OneExit0); A    -   Switch(cmd->type) { -   default: thefprintf (stderr,"Unknown runcmd\n"); -Exit (-1); -  -    Case ' ': +Ecmd = (structexeccmd*) cmd; -     if(ecmd->argv[0] ==0) +Exit0); A     //fprintf (stderr, "exec not implemented\n"); at     //Your code here ... -     if(Access (ecmd->argv[0], S_IXUSR | S_IRUSR) = =0) -     { -EXECV (ecmd->argv[0], ecmd->argv); -     } -     Else in     { -         if(ChDir ("/bin/") <0) to         { +printf"Change directory failed on line%d\n", __line__); -Exit0); the         } *EXECV (ecmd->argv[0], ecmd->argv); $     }Panax Notoginsengfprintf (stderr,"Execv ()%s failed in line%d\n", ecmd->argv[0], __line__); -      Break; the  +    Case '>': A    Case '<': theRcmd = (structredircmd*) cmd; +     //fprintf (stderr, "redir not implemented\n"); -     //Your code here ... $Close (rcmd->FD); $     if(Open (Rcmd->file, Rcmd->mode) <0) -     { -fprintf (stderr,"Try to open:%s failed\n", rcmd->file); theExit0); -     }WuyiRuncmd (rcmd->cmd); the      Break; -  Wu    Case '|': -Pcmd = (structpipecmd*) cmd; About     //fprintf (stderr, "Pipe not implemented\n"); $     //Your code here ... -     if(Pipe (P) <0) -     { -fprintf (stderr,"Call Syscall pipe () failed on line%d\n", __line__); AExit0); +     } the  -     if(Fork1 () = =0) $     { theClose1); theDUP (p[1]); theClose (p[0]); theClose (p[1]); -Runcmd (pcmd->Left ); in     } the  the     if(Fork1 () = =0) About     { theClose0); theDUP (p[0]); theClose (p[0]); +Close (p[1]); -Runcmd (pcmd->Right ); the     }Bayi  theClose (p[0]); theClose (p[1]); - wait (); - wait (); the      Break; the   }     the  theExit0); -}

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XV6-----Shell