Module optparse

Parse and process command line options.

In the common case, you can write the long-form help output typical of a modern-command line program, and let this module generate a custom parser that collects and diagnoses the options it describes.

The parser is an object instance which can then be tweaked for the uncommon case, by hand, or by using the on method to tie your custom handlers to options that are not handled quite the way you'd like.

Objects

OptionParser OptionParser prototype object.

Functions

optional (arglist, i[, value=true]) Option at arglist[i] can take an argument.
required (arglist, i[, value]) Option at arglist[i] requires an argument.
finished (arglist, i) Finish option processing

This is the handler automatically assigned to the option written as -- in the OptionParser spec argument.

flag (arglist, i[, value]) Option at arglist[i] is a boolean switch.
help () Option should display help text, then exit.
version () Option should display version text, then exit.
boolean (opt[, optarg="1"]) Return a Lua boolean equivalent of various optarg strings.
file (opt, optarg) Report an option parse error unless optarg names an existing file.
opterr (msg) Report an option parse error, then exit with status 2.
on_handler (arglist, i[, value=nil]) Function signature of an option handler for on.
on (name, handler, value) Add an option handler.
parse (arglist[, defaults]) Parse an argument list.
OptionParser_Init (spec) Signature for initialising a custom OptionParser.

Tables

boolvals Map various option strings to equivalent Lua boolean values.
opts Parsed options table, with a key for each encountered option, each with value set by that option's on_handler.
optparse Module table.

Metamethods

__index (name) Lazy loading of optparse submodules.


Objects

OptionParser
OptionParser prototype object.

Most often, after instantiating an OptionParser, everything else is handled automatically.

Then, calling parser:parse as shown below saves unparsed arguments into _G.arg (usually filenames or similar), and _G.opts will be a table of successfully parsed option values. The keys into this table are the long-options with leading hyphens stripped, and non-word characters turned to _. For example if --another-long had been found in the initial _G.arg, then _G.opts will have a key named another_long, with an appropriate value. If there is no long option name, then the short option is used, i.e. _G.opts.b will be set.

The values saved against those keys are controlled by the option handler, usually just true or the option argument string as appropriate.

Fields:

  • _init OptionParser_Init initialisation function
  • program string the first word following "Usage:" from spec
  • version string the last white-space delimited word on the first line of text from spec
  • versiontext string everything preceding "Usage:" from spec, and which will be displayed by the version on_handler
  • helptext string everything including and following "Usage:" from spec string and which will be displayed by the help on_handler

Usage:

    local optparse = require "optparse"
    
    local optparser = optparse [[
    any text VERSION
    Additional lines of text to show when the --version
    option is passed.
    
    Several lines or paragraphs are permitted.
    
    Usage: PROGNAME
    
    Banner text.
    
    Optional long description text to show when the --help
    option is passed.
    
    Several lines or paragraphs of long description are permitted.
    
    Options:
    
      -b                       a short option with no long option
          --long               a long option with no short option
          --another-long       a long option with internal hypen
          --really-long-option-name
                               with description on following line
      -v, --verbose            a combined short and long option
      -n, --dryrun, --dry-run  several spellings of the same option
      -u, --name=USER          require an argument
      -o, --output=[FILE]      accept an optional argument
          --version            display version information, then exit
          --help               display this help, then exit
    
    Footer text.  Several lines or paragraphs are permitted.
    
    Please report bugs at bug-list@yourhost.com
    ]]
    
    -- Note that `std.io.die` and `std.io.warn` will only prefix messages
    -- with `parser.program` if the parser options are assigned back to
    -- `_G.opts`:
    _G.arg, _G.opts = optparser:parse (_G.arg)

Functions

optional (arglist, i[, value=true])
Option at arglist[i] can take an argument. Argument is accepted only if there is a following entry that does not begin with a '-'.

This is the handler automatically assigned to options that have --opt=[ARG] style specifications in the OptionParser spec argument. You can also pass it as the handler argument to on for options you want to add manually without putting them in the OptionParser spec.

Like required, this handler will store multiple occurrences of a command-line option.

Parameters:

  • arglist table list of arguments
  • i int index of last processed element of arglist
  • value either a function to process the option argument, or a default value if encountered without an optarg (default true)

Returns:

    int index of next element of arglist to process

Usage:

    parser:on ("--enable-nls", parser.option, parser.boolean)
required (arglist, i[, value])

Option at arglist[i] requires an argument.

This is the handler automatically assigned to options that have --opt=ARG style specifications in the OptionParser spec argument. You can also pass it as the handler argument to on for options you want to add manually without putting them in the OptionParser spec.

Normally the value stored in the opt table by this handler will be the string given as the argument to that option on the command line. However, if the option is given on the command-line multiple times, opt["name"] will end up with all those arguments stored in the array part of a table:

 $ cat ./prog
 ...
 parser:on ({"-e", "-exec"}, required)
 _G.arg, _G.opt = parser:parse (_G.arg)
 print (tostring (_G.opt.exec))
 ...
 $ ./prog -e '(foo bar)' -e '(foo baz)' -- qux
 {1=(foo bar),2=(foo baz)}

Parameters:

  • arglist table list of arguments
  • i int index of last processed element of arglist
  • value either a function to process the option argument, or a forced value to replace the user's option argument. (optional)

Returns:

    int index of next element of arglist to process

Usage:

    parser:on ({"-o", "--output"}, parser.required)
finished (arglist, i)
Finish option processing

This is the handler automatically assigned to the option written as -- in the OptionParser spec argument. You can also pass it as the handler argument to on if you want to manually add an end of options marker without writing it in the OptionParser spec.

This handler tells the parser to stop processing arguments, so that anything after it will be an argument even if it otherwise looks like an option.

Parameters:

  • arglist table list of arguments
  • i int index of last processed element of arglist

Returns:

    int index of next element of arglist to process

Usage:

    parser:on ("--", parser.finished)
flag (arglist, i[, value])
Option at arglist[i] is a boolean switch.

This is the handler automatically assigned to options that have --long-opt or -x style specifications in the OptionParser spec argument. You can also pass it as the handler argument to on for options you want to add manually without putting them in the OptionParser spec.

Beware that, unlike required, this handler will store multiple occurrences of a command-line option as a table only when given a value function. Automatically assigned handlers do not do this, so the option will simply be true if the option was given one or more times on the command-line.

Parameters:

  • arglist table list of arguments
  • i int index of last processed element of arglist
  • value either a function to process the option argument, or a value to store when this flag is encountered (optional)

Returns:

    int index of next element of arglist to process

Usage:

    parser:on ({"--long-opt", "-x"}, parser.flag)
help ()
Option should display help text, then exit.

This is the handler automatically assigned tooptions that have --help in the specification, e.g. -h, -?, --help.

Usage:

    parser:on ("-?", parser.version)
version ()
Option should display version text, then exit.

This is the handler automatically assigned tooptions that have --version in the specification, e.g. -V, --version.

Usage:

    parser:on ("-V", parser.version)
boolean (opt[, optarg="1"])
Return a Lua boolean equivalent of various optarg strings. Report an option parse error if optarg is not recognised.

Pass this as the value function to on when you want various "truthy" or "falsey" option arguments to be coerced to a Lua true or false respectively in the options table.

Parameters:

Returns:

    bool true or false

Usage:

    parser:on ("--enable-nls", parser.optional, parser.boolean)
file (opt, optarg)
Report an option parse error unless optarg names an existing file.

Pass this as the value function to on when you want to accept only option arguments that name an existing file.

Parameters:

  • opt string option name
  • optarg string option argument, must be an existing file

Returns:

    string optarg

Usage:

    parser:on ("--config-file", parser.required, parser.file)
opterr (msg)
Report an option parse error, then exit with status 2.

Use this in your custom option handlers for consistency with the error output from built-in optparse error messages.

Parameters:

on_handler (arglist, i[, value=nil])
Function signature of an option handler for on.

Parameters:

  • arglist table list of arguments
  • i int index of last processed element of arglist
  • value additional value registered with on (default nil)

Returns:

    int index of next element of arglist to process
on (name, handler, value)
Add an option handler.

When the automatically assigned option handlers don't do everything you require, or when you don't want to put an option into the OptionParser spec argument, use this function to specify custom behaviour. If you write the option into the spec argument anyway, calling this function will replace the automatically assigned handler with your own.

When writing your own handlers for optparse:on, you only need to deal with normalised arguments, because combined short arguments (-xyz), equals separators to long options (--long=ARG) are fully expanded before any handler is called.

Parameters:

  • name opts of the option, or list of option names
  • handler on_handler function to call when any of opts is encountered
  • value additional value passed to on_handler

Usage:

    -- Don't process any arguments after `--`
    parser:on ('--', parser.finished)
parse (arglist[, defaults])
Parse an argument list.

Parameters:

  • arglist table list of arguments
  • defaults table table of default option values (optional)

Returns:

  1. table a list of unrecognised arglist elements
  2. opts parsing results
OptionParser_Init (spec)
Signature for initialising a custom OptionParser.

Read the documented options from spec and return custom parser that can be used for parsing the options described in spec from a run-time argument list. Options in spec are recognised as lines that begin with at least two spaces, followed by a hyphen.

Parameters:

  • spec string option parsing specification

Returns:

    OptionParser a parser for options described by spec

Usage:

    customparser = optparse (optparse_spec)

Tables

boolvals
Map various option strings to equivalent Lua boolean values.

Fields:

  • false false
  • 0 false
  • no false
  • n false
  • true true
  • 1 true
  • yes true
  • y true
opts
Parsed options table, with a key for each encountered option, each with value set by that option's on_handler. Where an option has one or more long-options specified, the key will be the first one of those with leading hyphens stripped and non-alphanumeric characters replaced with underscores. For options that can only be specified by a short option, the key will be the letter of the first of the specified short options:

 {"-e", "--eval-file"} => opts.eval_file
 {"-n", "--dryrun", "--dry-run"} => opts.dryrun
 {"-t", "-T"} => opts.t

Generally there will be one key for each previously specified option (either automatically assigned by OptionParser or added manually with on) containing the value(s) assigned by the associated on_handler. For automatically assigned handlers, that means true for straight-forward flags and optional-argument options for which no argument was given; or else the string value of the argument passed with an option given only once; or a table of string values of the same for arguments given multiple times.

 ./prog -x -n -x => opts = { x = true, dryrun = true }
 ./prog -e '(foo bar)' -e '(foo baz)'
     => opts = {eval_file = {"(foo bar)", "(foo baz)"} }

If you write your own handlers, or otherwise specify custom handling of options with on, then whatever value those handlers return will be assigned to the respective keys in opts.

optparse
Module table.

Fields:

  • version string release version identifier

Metamethods

__index (name)
Lazy loading of optparse submodules. Don't load everything on initial startup, wait until first attempt to access a submodule, and then load it on demand.

Parameters:

Returns:

    table or nil the submodule that was loaded to satisfy the missing name, otherwise nil if nothing was found

Usage:

    local optparse = require "optparse"
    local version = optparse.version
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