path: root/README.md

Slop
====

Slop is a simple option parser with an easy to remember syntax and friendly API.

Version 4 of Slop is aimed at Ruby 2.0 or later. Please use
[Version 3](https://github.com/leejarvis/slop/tree/v3) for Ruby 1.9 support.

[![Build Status](https://travis-ci.org/leejarvis/slop.svg?branch=master)](http://travis-ci.org/leejarvis/slop)

Installation
------------

    gem install slop

Usage
-----

```ruby
opts = Slop.parse do |o|
  o.string '-h', '--host', 'a hostname'
  o.integer '--port', 'custom port', default: 80
  o.bool '-v', '--verbose', 'enable verbose mode'
  o.bool '-q', '--quiet', 'suppress output (quiet mode)'
  o.bool '-c', '--check-ssl-certificate', 'check SSL certificate for host'
  o.on '--version', 'print the version' do
    puts Slop::VERSION
    exit
  end
end

ARGV #=> -v --host 192.168.0.1 --check-ssl-certificate

opts[:host]                 #=> 192.168.0.1
opts.verbose?               #=> true
opts.quiet?                 #=> false
opts.check_ssl_certificate? #=> true

opts.to_hash  #=> { host: "192.168.0.1", port: 80, verbose: true, quiet: false, check_ssl_certificate: true }
```

Option types
------------

Built in Option types are as follows:

```ruby
o.string  #=> Slop::StringOption, expects an argument
o.bool    #=> Slop::BoolOption, no argument, aliased to BooleanOption
o.integer #=> Slop::IntegerOption, expects an argument, aliased to IntOption
o.float   #=> Slop::FloatOption, expects an argument
o.array   #=> Slop::ArrayOption, expects an argument
o.regexp  #=> Slop::RegexpOption, expects an argument
o.null    #=> Slop::NullOption, no argument and ignored from `to_hash`
o.on      #=> alias for o.null
```

You can see all built in types in `slop/types.rb`. Suggestions or pull requests
for more types are welcome.

Advanced Usage
--------------

This example is really just to describe how the underlying API works.
It's not necessarily the best way to do it.

```ruby
opts = Slop::Options.new
opts.banner = "usage: connect [options] ..."
opts.separator ""
opts.separator "Connection options:"
opts.string "-H", "--hostname", "a hostname"
opts.int "-p", "--port", "a port", default: 80
opts.separator ""
opts.separator "Extra options:"
opts.array "--files", "a list of files to import"
opts.bool "-v", "--verbose", "enable verbose mode", default: true

parser = Slop::Parser.new(opts)
result = parser.parse(["--hostname", "192.168.0.1", "--no-verbose"])

result.to_hash #=> { hostname: "192.168.0.1", port: 80,
                 #     files: [], verbose: false }

puts opts # prints out help
```

Arguments
---------

It's common to want to retrieve an array of arguments that were not processed
by the parser (i.e options or consumed arguments). You can do that with the
`Result#arguments` method:

```ruby
args = %w(connect --host google.com GET)
opts = Slop.parse args do |o|
  o.string '--host'
end

p opts.arguments #=> ["connect", "GET"] # also aliased to `args`
```

This is particularly useful when writing scripts with `ARGF`:

```ruby
opts = Slop.parse do |blah|
  # ...
end

# make sure sloptions aren't consumed by ARGF
ARGV.replace opts.arguments

ARGF.each { |line|
  # ...
}
```

Arrays
------

Slop has a built in `ArrayOption` for handling array values:

```ruby
opts = Slop.parse do |o|
  # the delimiter defaults to ','
  o.array '--files', 'a list of files', delimiter: ','
end

# both of these will return o[:files] as ["foo.txt", "bar.rb"]:
# --files foo.txt,bar.rb
# --files foo.txt --files bar.rb
```

If you want to disable the built-in string-splitting, set the delimiter to
`nil`.

Custom option types
-------------------

Slop uses option type classes for every new option added. They default to the
`NullOption`. When you type `o.array` Slop looks for an option called
`Slop::ArrayOption`. This class must contain at least 1 method, `call`. This
method is executed at parse time, and the return value of this method is
used for the option value. We can use this to build custom option types:

```ruby
module Slop
  class PathOption < Option
    def call(value)
      Pathname.new(value)
    end
  end
end

opts = Slop.parse %w(--path ~/) do |o|
  o.path '--path', 'a custom path name'
end

p opts[:path] #=> #<Pathname:~/>
```

Custom options can also implement a `finish` method. This method by default
does nothing, but it's executed once *all* options have been parsed. This
allows us to go back and mutate state without having to rely on options
being parsed in a particular order. Here's an example:

```ruby
module Slop
  class FilesOption < ArrayOption
    def finish(opts)
      if opts.expand?
        self.value = value.map { |f| File.expand_path(f) }
      end
    end
  end
end

opts = Slop.parse %w(--files foo.txt,bar.rb -e) do |o|
  o.files '--files', 'an array of files'
  o.bool '-e', '--expand', 'if used, list of files will be expanded'
end

p opts[:files] #=> ["/full/path/foo.txt", "/full/path/bar.rb"]
```

Errors
------

Slop will raise errors for the following:

* An option used without an argument when it expects one: `Slop::MissingArgument`
* An option used that Slop doesn't know about: `Slop::UnknownOption`

These errors inherit from `Slop::Error`, so you can rescue them all.
Alternatively you can suppress these errors with the `suppress_errors` config
option:

```ruby
opts = Slop.parse suppress_errors: true do
  o.string '-name'
end

# or per option:

opts = Slop.parse do
  o.string '-host', suppress_errors: true
  o.int '-port'
end
```

Printing help
-------------

The return value of `Slop.parse` is a `Slop::Result` which provides a nice
help string to display your options. Just `puts opts` or call `opts.to_s`:

```ruby
opts = Slop.parse do |o|
  o.string '-h', '--host', 'hostname'
  o.int '-p', '--port', 'port (default: 80)', default: 80
  o.string '--username'
  o.separator ''
  o.separator 'other options:'
  o.bool '--quiet', 'suppress output'
  o.on '-v', '--version' do
    puts "1.1.1"
  end
end

puts opts
```

Output:

```
% ruby run.rb
usage: run.rb [options]
    -h, --host     hostname
    -p, --port     port (default: 80)
    --username

other options:
    --quiet        suppress output
    -v, --version
```

This method takes an optional `prefix` value, which defaults to `" " * 4`:

```
puts opts.to_s(prefix: "  ")
```

It'll deal with aligning your descriptions according to the longest option
flag.

Here's an example of adding your own help option:

```ruby
o.on '--help' do
  puts o
  exit
end
```

Commands
--------

As of version 4, Slop does not have built in support for git-style subcommands.
You can use version 3 of Slop (see `v3` branch). I also expect there to be some
external libraries released soon that wrap around Slop to provide support for
this feature. I'll update this document when that happens.

Upgrading from version 3
------------------------

Slop v4 is completely non-backwards compatible. The code has been rewritten
from the ground up. If you're already using version 3 you *have* to update
your code to use version 4. Here's an overview of the more fundamental changes:

#### No more `instance_eval`

Before:

```ruby
Slop.parse do
  on 'v', 'version' do
    puts VERSION
  end
end
```

After:

```ruby
Slop.parse do |o|
  o.on '-v', '--version' do
    puts VERSION
  end
end
```

#### No more `as` for option types

Instead, the type is declared in the method call. Before:

```ruby
on 'port=', as: Integer
```

After:

```ruby
o.int '--port' # or integer
```

See the custom types section of the document.

#### No more trailing `=`

Instead, the "does this option expect an argument" question is answered by
the option type (i.e `on` and `bool` options do not expect arguments, all
others do. They handle type conversion, too.

#### Hyphens are required

This was a hard decision to make, but you must provide prefixed hyphens when
declaring your flags. This makes the underlying code much nicer and much less
ambiguous, which leads to less error prone code. It also means you can easily
support single hyphen prefix for a long flag, i.e `-hostname` which you
could not do before. It also provides a hidden feature, which is infinity flag
aliases: `o.string '-f', '-x', '--foo', '--bar', 'this is insane'`

#### Strict is now on by default

v3 had a `strict` option. v4 has no such option, and to suppress errors you can
instead provide the `suppress_errors: true` option to Slop.

#### No more parse!

Where v3 has both `Slop.parse` and `Slop.parse!`, v4 only has `parse`. The
former was used to decide whether Slop should or should not mutate the
original args (usually ARGV). This is almost never what you want, and it
can lead to confusion. Instead, `Slop::Result` provides an `arguments`
methods:

```ruby
opts = Slop.parse do |o|
  o.string '--hostname', '...'
end

# ARGV is "hello --hostname foo bar"
p opts.arguments #=> ["hello", "bar"]
```