getopt

Documentation

Overview

Package getopt is the gopy port of cpython/Python/getopt.c. CPython ships its own getopt to dodge GNU getopt's locale and global-state quirks; the interpreter init code (Modules/main.c, pylifecycle.c) calls _PyOS_GetOpt to walk argv before pyinit_core runs.

The three module globals (_PyOS_opterr, _PyOS_optind, _PyOS_optarg) and the static opt_ptr collapse into State so the parser is re-entrant. argv is []string instead of wchar_t*-array because gopy already decoded os.Args to UTF-8 during pre-config.

CPython: Python/getopt.c

Index

• Constants
• Variables
• type LongOption
• type State
  • func New() *State
  • func (s *State) GetOpt(argv []string, shortOpts string, longOpts []LongOption) int

Constants

const EOF = -1

EOF marks "no more options". Mirrors the -1 _PyOS_GetOpt returns when argv is exhausted or the next argument is non-option.

CPython: Python/getopt.c:67 (return -1)

const ErrorMark = '_'

ErrorMark is the int the parser returns on a parse error. Mirrors the '_' sentinel _PyOS_GetOpt picks for the same.

CPython: Python/getopt.c:119 (return '_')

const PythonShortOpts = "bBc:dEhiIm:OPqRsStuvVW:xX:?"

PythonShortOpts is the SHORT_OPTS string from getopt.c. Pinned here so the cmd/gopy entry point can use the exact CPython 3.14 option set.

CPython: Python/getopt.c:40 SHORT_OPTS

Variables

var PythonLongOpts = []LongOption{
	{Name: "check-hash-based-pycs", HasArg: true, Val: 0},
	{Name: "help-all", HasArg: false, Val: 1},
	{Name: "help-env", HasArg: false, Val: 2},
	{Name: "help-xoptions", HasArg: false, Val: 3},
}

PythonLongOpts mirrors the longopts table in getopt.c. The trailing `{NULL, 0, -1}` C sentinel is implicit in Go because the slice carries its own length.

CPython: Python/getopt.c:42 longopts

Types

type LongOption

type LongOption struct {
	Name   string
	HasArg bool
	Flag   *int
	Val    int
}

LongOption mirrors the static longopts entries in cpython/Python/getopt.c. Flag is kept for source-shape parity but no caller in gopy uses the flag-pointer mode (matches CPython's own usage where every entry sets flag=NULL).

CPython: Include/internal/pycore_getopt.h _PyOS_LongOption

type State

type State struct {
	OptInd int
	OptArg string
	OptErr bool
	// LongIndex is set to the longopts entry that matched on the
	// most recent --name return. Mirrors *longindex.
	//
	// CPython: Python/getopt.c:60 longindex parameter
	LongIndex int
	// Stderr is where parse-error messages go when OptErr is true.
	// Defaults to os.Stderr; tests can swap it for a buffer.
	Stderr io.Writer
	// contains filtered or unexported fields
}

State carries the per-parse cursor. Each GetOpt call advances OptInd / OptArg / optPtr; OptErr controls whether parse errors print to Stderr.

CPython: Python/getopt.c:32 _PyOS_opterr / 33 _PyOS_optind / 34 _PyOS_optarg / 36 opt_ptr

func New

func New() *State

New returns a State initialized the way _PyOS_ResetGetOpt leaves the globals: opterr=true, optind=1, optarg="", opt_ptr="".

CPython: Python/getopt.c:52 _PyOS_ResetGetOpt

func (*State) GetOpt

func (s *State) GetOpt(argv []string, shortOpts string, longOpts []LongOption) int

GetOpt parses one option from argv starting at s.OptInd. Returns the option char (positive int), 0 when the long-option's flag was set, EOF at end-of-options, or ErrorMark on a parse error. argv[0] is treated as the program name and never inspected, matching the _PyOS_optind=1 starting cursor.

CPython: Python/getopt.c:60 _PyOS_GetOpt