A KISS pure Fortran Library for building powerful, easy-to-use, elegant command line interfaces

• FLAP is a pure Fortran (KISS) library for building easily nice Command Line Interfaces (CLI) for modern Fortran projects;
• FLAP is Fortran 2003+ standard compliant;
• FLAP is OOP designed;
• FLAP is a Free, Open Source Project.

Modern Fortran standards (2003+) have introduced support for Command Line Arguments (CLA), thus it is possible to construct nice and effective Command Line Interfaces (CLI). FLAP is a small library designed to simplify the (repetitive) construction of complicated CLI in pure Fortran (standard 2003+). FLAP has been inspired by the python module argparse trying to mimic it. Once you have defined the arguments that are required by means of a user-friendly method of the CLI, FLAP will parse the CLAs for you. It is worthy of note that FLAP, as argparse, also automatically generates help and usage messages and issues errors when users give the program invalid arguments.

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FLAP is inspired by the python great module argparse, thus many features are taken from it. Here the main features are listed.

• User-friendly methods for building flexible and effective Command Line Interfaces (CLI);
• comprehensive Command Line Arguments (CLA) support:
  • support optional and non optional CLA;
  • support boolean CLA;
  • support positional CLA;
  • support list of allowable values for defined CLA with automatic consistency check;
  • support multiple valued (list of values) CLA;
  • self-consistency-check of CLA definition;
• automatic generation of help and usage messages;
• consistency-check of whole CLI definition;
• errors trapping for invalid CLI usage;
• replicate all the useful features of argparse;
• implement docopt features.

Any feature request is welcome.

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FLAP is an open source project, it is distributed under the GPL v3. Anyone is interest to use, to develop or to contribute to FLAP is welcome.

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Besides this README file the FLAP documentation is contained into its own wiki. Detailed documentation of the API is contained into the GitHub Pages that can also be created locally by means of ford tool.

Running the provided test program, flap_test -h, a taste of FLAP is served:

+--> flap_test, a testing program for FLAP library
+--> Parsing Command Line Arguments
|--> The Command Line Interface (CLI) has the following options
|-->   flap_test  [value] --string value [--integer value] [--real value] [--boolean] [--boolean_val value] [--integer_list value#1 value#2 value#3] [--help] [--version]
|--> Each Command Line Argument (CLA) has the following meaning:
|-->   [value]
|-->     Positional real input
|-->     It is a positional CLA having position "1-th"
|-->     It is a optional CLA which default value is "1.0"
|-->   [--string value] or [-s value]
|-->     String input
|-->     It is a non optional CLA thus must be passed to CLI
|-->   [--integer value] or [-i value] with value chosen in: (1,3,5)
|-->     Integer input with fixed range
|-->     It is a optional CLA which default value is "1"
|-->   [--real value] or [-r value]
|-->     Real input
|-->     It is a optional CLA which default value is "1.0"
|-->   [--boolean] or [-b]
|-->     Boolean input
|-->     It is a optional CLA which default value is ".false."
|-->   [--boolean_val value] or [-bv value]
|-->     Valued boolean input
|-->     It is a optional CLA which default value is ".true."
|-->   [--integer_list value#1 value#2 value#3] or [-il value#1 value#2 value#3]
|-->     Integer list input
|-->     It is a optional CLA which default value is "1 8 32"
|-->   [--help] or [-h]
|-->     Print this help message
|-->     It is a optional CLA
|-->   [--version] or [-v]
|-->     Print version
|-->     It is a optional CLA
|--> Usage examples:
|-->   -) flap_test -s 'Hello FLAP'
|-->   -) flap_test -s 'Hello FLAP' -i -2 # printing error...
|-->   -) flap_test -s 'Hello FLAP' -i 3 -r 33.d0
|-->   -) flap_test -s 'Hello FLAP' -integer_list 10 -3 87
|-->   -) flap_test 33.0 -s 'Hello FLAP' -i 5
|-->   -) flap_test -string 'Hello FLAP' -boolean

Not so bad for just a very few statements as the following:

...
write(stdout,'(A)')'+--> flap_test, a testing program for FLAP library'
! initializing CLI
call cli%init(progname='flap_test',                                           &
              version ='v0.0.1',                                              &
              examples=["flap_test -s 'Hello FLAP'                          ",&
                        "flap_test -s 'Hello FLAP' -i -2 # printing error...",&
                        "flap_test -s 'Hello FLAP' -i 3 -r 33.d0            ",&
                        "flap_test -s 'Hello FLAP' -integer_list 10 -3 87   ",&
                        "flap_test 33.0 -s 'Hello FLAP' -i 5                ",&
                        "flap_test -string 'Hello FLAP' -boolean            "])
! setting CLAs
call cli%add(pref='|-->',switch='--string',      switch_ab='-s', help='String input',                  required=.true., act='store',                                  error=error)
call cli%add(pref='|-->',switch='--integer',     switch_ab='-i', help='Integer input with fixed range',required=.false.,act='store',          def='1',choices='1,3,5',error=error)
call cli%add(pref='|-->',switch='--real',        switch_ab='-r', help='Real input',                    required=.false.,act='store',          def='1.0',              error=error)
call cli%add(pref='|-->',switch='--boolean',     switch_ab='-b', help='Boolean input',                 required=.false.,act='store_true',     def='.false.',          error=error)
call cli%add(pref='|-->',switch='--boolean_val', switch_ab='-bv',help='Valued boolean input',          required=.false.,act='store',          def='.true.',           error=error)
call cli%add(pref='|-->',switch='--integer_list',switch_ab='-il',help='Integer list input',            required=.false.,act='store',nargs='3',def='1 8 32',           error=error)
call cli%add(pref='|-->',positional=.true.,position=1,           help='Positional real input',         required=.false.,                      def='1.0',              error=error)
! parsing CLI
write(stdout,'(A)')'+--> Parsing Command Line Arguments'
call cli%parse(error=error,pref='|-->')
...

For a practical example of FLAP usage see POG source file at line 85.

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In the following the changelog of most important releases is reported.

Stable Release. Fully backward compatible.

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