CS252-Shell-Project/shell.y at main · code-help-tutor/CS252-Shell-Project · GitHub

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/*
 * CS-252
 * shell.y: parser for shell
 *
 * This parser compiles the following grammar:
 *
 *	cmd [arg]* [> filename]
 *
 * you must extend it to understand the complete shell grammar
 *
 */

%code requires
{
#include <string>

#if __cplusplus > 199711L
#define register      // Deprecated in C++11 so remove the keyword
#endif
}

%union
{
  char        *string_val;
  // Example of using a c++ type in yacc
  std::string *cpp_string;
}

%token <cpp_string> WORD
%token NOTOKEN GREAT GREATGREAT GREATAMPERSAND GREATGREATAMPERSAND
%token AMPERSAND PIPE LESS NEWLINE IF FI THEN LBRACKET RBRACKET SEMI
%token DO DONE WHILE FOR IN

%{
//#define yylex yylex
#include <cstdio>
#include "Shell.hh"

void yyerror(const char * s);
int yylex();

%}

%%

goal: command_list;

arg_list:
        arg_list WORD {
          Shell::TheShell->_simpleCommand->insertArgument( $2 ); }
        | /*empty string*/
	;

cmd_and_args:
  	WORD {
          Shell::TheShell->_simpleCommand = new SimpleCommand();
          Shell::TheShell->_simpleCommand->insertArgument( $1 );
        }
        arg_list
	;

pipe_list:
        cmd_and_args
	    {
		Shell::TheShell->_pipeCommand->insertSimpleCommand(
		    Shell::TheShell->_simpleCommand );
		Shell::TheShell->_simpleCommand = new SimpleCommand();
	    }
	| pipe_list PIPE cmd_and_args
	    {
	    }
	;

io_modifier:
	   GREATGREAT WORD
	 | GREAT WORD
	    {
		Shell::TheShell->_pipeCommand->_outFile = $2;
	    }
	 | GREATGREATAMPERSAND WORD
	 | GREATAMPERSAND WORD
	 | LESS WORD
	;

io_modifier_list:
	io_modifier_list io_modifier
	| /*empty*/
	;

background_optional:
	AMPERSAND
	| /*empty*/
	;

SEPARATOR:
	NEWLINE
	| SEMI
	;

command_line:
	 pipe_list io_modifier_list background_optional SEPARATOR
         {
	    Shell::TheShell->_listCommands->
		insertCommand(Shell::TheShell->_pipeCommand);
	    Shell::TheShell->_pipeCommand = new PipeCommand();
         }
        | if_command SEPARATOR
         {
	    Shell::TheShell->_listCommands->
		insertCommand(Shell::TheShell->_ifCommand);
         }
        | while_command SEPARATOR {printf("while\n"); }
        | for_command SEPARATOR {printf("for\n"); }
        | SEPARATOR /*accept empty cmd line*/
        | error SEPARATOR {yyerrok; Shell::TheShell->clear(); }
	;          /*error recovery*/

command_list :
     command_line
	{
	   Shell::TheShell->execute();
	}
     |
     command_list command_line
	{
	    Shell::TheShell->execute();
	}
     ;  /* command loop*/

if_command:
    IF LBRACKET
	{
	    Shell::TheShell->_level++;
	    Shell::TheShell->_ifCommand = new IfCommand();
	}
    arg_list RBRACKET SEMI THEN
	{
	    Shell::TheShell->_ifCommand->insertCondition(
		    Shell::TheShell->_simpleCommand);
	    Shell::TheShell->_simpleCommand = new SimpleCommand();
	}
    command_list FI
	{
	    Shell::TheShell->_level--;
	    Shell::TheShell->_ifCommand->insertListCommands(
		    Shell::TheShell->_listCommands);
	    Shell::TheShell->_listCommands = new ListCommands();
	}
    ;

while_command:
    WHILE LBRACKET arg_list RBRACKET SEMI DO command_list DONE
    ;

for_command:
    FOR WORD IN arg_list SEMI DO command_list DONE
    ;

%%

void
yyerror(const char * s)
{
  fprintf(stderr,"%s", s);
}

#if 0
main()
{
  yyparse();
}
#endif