parser(1)	       Grass User's Manual		parser(1)



NNAAMMEE
       GGRRAASSSS  ppaarrsseerr  iinntteerrffaaccee   -  A set of GRASS routines that
       standardizes GRASS commands.

DDEESSCCRRIIPPTTIIOONN
       A set of routines in GRASS provides a mechanism	for  com-
       mand-line  parsing. The routines standardize commands that
       expect command-line arguments.  When a  user  is  familiar
       with  the general form of command-line input as defined by
       the parser, it simplifies the necessity of remembering (or
       at least guessing) required command-line arguments for any
       GRASS command.


       The parser behaves in one of three ways:

	      If no command-line arguments  are  entered  by  the
	      user,  the  parser searches for an interactive ver-
	      sion of the command. If it  is  found,  control  is
	      passed  over  to this interactive version. If it is
	      not found, the parser prompts the user for program-
	      mer-defined  options and flags. This prompting con-
	      forms to the same standard for every GRASS  command
	      that uses the parser routines.



	      If  command-line	arguments  are entered but do not
	      include all the options and flags that the program-
	      mer has defined as required arguments, three things
	      happen:

	      the parser passes an  error  message  to	the  user
	      indicating which required options and/or flags were
	      missing from the command-line,

	      then the parser displays a complete  usage  message
	      for that command, and finally

	       the parser cancels execution of the command.




	      If  all  necessary options and flags are entered on
	      the command line by the user, the  parser  executes
	      the command with the given options and flags.



       _T_h_i_s _p_a_g_e _w_a_s _d_e_r_i_v_e_d _f_r_o_m _t_h_e GRASS 4.1 Programmer's Man-
       ual, Command-Line Parsing, _w_h_i_c_h _o_f_f_e_r_s _d_e_t_a_i_l_e_d  _i_n_f_o_r_m_a_-
       _t_i_o_n _a_b_o_u_t _t_h_e _G_R_A_S_S _p_a_r_s_i_n_g _r_o_u_t_i_n_e_s_.

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GRASS 5.0						parser(1)
