Output Formats

In addition to the automatic help and version messages, FLAP can export your CLI definition in three structured formats: man page, bash completion script, and Markdown.

Automatic help and usage

Help is printed automatically when --help (or -h) is passed. The message includes:

• The usage line derived from all defined arguments
• The program description (from cli%init)
• Required and optional switches, each with their help text and default values
• The list of subcommands (if any) with per-command help hints
• Examples (if provided to cli%init)
• The epilog (if provided)

$ ./myapp --help
usage:  myapp --input value [--output value] [--verbose] [--help] [--version]

A demonstration program

Required switches:
   --input value, -i value
          Input file path

Optional switches:
   --output value, -o value
          default value out.dat
          Output file path
   --verbose, -v
          default value .false.
          Enable verbose output
   --help, -h
          Print this help message
   --version, -v
          Print version

Examples:
   myapp -i data.dat
   myapp -i data.dat -o result.dat --verbose

Man page — cli%save_man_page

Generate a Unix man page from your CLI definition:

call cli%save_man_page(man_file='myapp.1', error=error)

The produced file (myapp.1 by convention for section 1 commands) can be installed in the system man path or shipped with your software package.

Full example:

program myapp
  use flap
  implicit none
  type(command_line_interface) :: cli
  integer                      :: error

  call cli%init(progname='myapp', version='v1.0', &
                description='A demonstration program')
  call cli%add(switch='--input', switch_ab='-i', &
               help='Input file', required=.true., act='store', error=error)

  call cli%parse(error=error)
  if (error /= 0) stop

  ! export man page
  call cli%save_man_page(man_file='myapp.1', error=error)
  if (error /= 0) stop
end program myapp

Install and view:

man ./myapp.1

Bash completion — cli%save_bash_completion

Generate a bash completion script so users get tab-completion for your program:

call cli%save_bash_completion(completion_file='myapp.bash', error=error)

To activate it in the current shell:

source myapp.bash

For permanent installation, place the file in /etc/bash_completion.d/ or ~/.bash_completion.d/:

cp myapp.bash ~/.bash_completion.d/myapp

Markdown usage export — cli%save_usage_to_markdown

Export the usage message as a Markdown file, suitable for embedding in documentation or wikis:

call cli%save_usage_to_markdown(md_file='usage.md', error=error)

The output is formatted Markdown with code blocks for the usage line and argument tables.

Printing usage programmatically — cli%print_usage

Print the usage message to stdout at any point in your program:

call cli%print_usage()

This is equivalent to the user passing --help, but it does not trigger program exit — you control the flow.

Summary of export methods

Method	Output	Typical filename
cli%save_man_page	Unix man page (troff format)	myapp.1
cli%save_bash_completion	Bash completion script	myapp.bash
cli%save_usage_to_markdown	Markdown usage page	usage.md
cli%print_usage	Prints help to stdout	—