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C Library Functions  - M_args (3)

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NAME

M_args(3fm) - [ARGUMENTS::M_args::INTRO] - define a NAMELIST in a module template to provide command line argument parsing (LICENSE:PD)

CONTENTS

Synopsis
Description
Example
Author
License

SYNOPSIS

Usage:

     use M_args, only : get_namelist, print_dictionary, unnamed
     use M_args, only : get_command_arguments_as_raw_namelist
     use M_args, only : get_command_arguments_stack
     use M_args, only : get_command_arguments_string
     use M_args, only : longest_command_argument
     use M_args, only : debug
     use M_args, only : oneline

DESCRIPTION

Use the M_arguments(3fp) module template in the following example program to allow for command line parsing much like standard Unix command line parsing. Just change the variables defined in the NAMELIST. There are further details in the documentation for get_namelist(3f) and print_dictionary(3f), but for basic use starting with the example program should be sufficient.

Then, your program can be called with forms like:

    cmd -x 1.0 -y -20 --points 1,2,3 -title ’This is my title’
    cmd --help *.data

A variable of the form LETTER_ becomes the uppercase keyword -LETTER, and negative values do not need quoted as values. Single-letter keywords are assumed to be used on the command line as short options with a single dash prefix, while multi-letter keywords are assumed to be long options. variable names may be equivalenced to allow for short and long versions of a keyword.

EXAMPLE

Sample program

   !program demo_M_args
   module M_arguments
   use M_args,    only : get_namelist, print_dictionary, unnamed, oneline

   ! >>> CHANGE THIS
   ! declare and initialize a namelist. Letter_ denotes an uppercase short command keyword
   real              :: x=111.1, y=222.2, z=333.3
   real              :: point(3)=[10.0,20.0,30.0]
   character(len=80) :: title=" "
   logical           :: l=.false., l_=.false.
   logical           :: help=.false., version=.false., v=.false., h=.false.
   equivalence       (help,h),(version,v)
   namelist /args/ x,y,z,point,title,help,h,version,v,l,l_
   ! << END OF CHANGES

   contains
      subroutine get_args()
      integer :: ios
      character(len=255) :: message ! use for I/O error messages
      character(len=:),allocatable :: readme  ! stores updated namelist
      character(len=10000) :: hold_namelist(60)
         hold_namelist=’’
         write(hold_namelist,nml=args,iostat=ios,iomsg=message)
         if(ios.eq.0)then
            readme=get_namelist(oneline(hold_namelist))
            read(readme,nml=args,iostat=ios,iomsg=message)
         endif
         if(ios.ne.0)then
            write(*,’("ERROR:",i0,1x,a)’)ios, trim(message)
            call print_dictionary()
            stop 1
         endif
      end subroutine get_args
   end module M_arguments

   program short
   use M_arguments, only : get_args, unnamed
   use M_arguments  ! make user variables available
   implicit none
   integer :: i
      call get_args()  ! crack command line options
      ! >> USER YOUR VARIABLES HERE. FOR EXAMPLE:
      write(*,*)’VALUES ARE NOW ’, new_line(’A’),&
      &’x        ’,x,              new_line(’A’),&
      &’y        ’,y,              new_line(’A’),&
      &’z        ’,z,              new_line(’A’),&
      &’point    ’,point,          new_line(’A’),&
      &’title    ’,title,          new_line(’A’),&
      &’help     ’,help,’h ’,h,    new_line(’A’),&
      &’version  ’,version,’v ’,v, new_line(’A’),&
      &’l        ’,l,              new_line(’A’),&
      &’l_       ’,l_
      if(size(unnamed).gt.0)then
         write(*,’(a)’)’UNNAMED:’
         write(*,’(i6.6,3a)’)(i,’[’,unnamed(i),’]’,i=1,size(unnamed))
      endif
      !<< END OF EXAMPLE USAGE OF VARIABLES
   end program short
   !end program demo_M_args

AUTHOR

John S. Urban, 2019

LICENSE

Public Domain

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Nemo Release 3.1

M_args (3)

July 22, 2023

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