\input texinfo @c -*-texinfo-*-
@c %**start of header
@setfilename arg_parser.info
@documentencoding ISO-8859-15
@settitle Arg_parser Manual
@finalout
@c %**end of header

@set UPDATED 5 February 2022
@set VERSION 1.17

@dircategory Libraries
@direntry
* Arg_parser: (arg_parser).     A POSIX/GNU command line argument parser
@end direntry


@ifnothtml
@titlepage
@title Arg_parser
@subtitle A POSIX/GNU command line argument parser
@subtitle for Arg_parser version @value{VERSION}, @value{UPDATED}
@author by Antonio Diaz Diaz

@page
@vskip 0pt plus 1filll
@end titlepage

@contents
@end ifnothtml

@ifnottex
@node Top
@top

This manual is for Arg_parser (version @value{VERSION}, @value{UPDATED}).

@menu
* Introduction::        Purpose and features of Arg_parser
* Argument syntax::     By convention, options start with a hyphen
* Initialization::      Parsing arguments and reporting errors
* Using Arg_parser::    Reading the options and arguments parsed
* C version::           Using the C version of Arg_parser
* Problems::            Reporting bugs
* Concept index::       Index of concepts
@end menu

@sp 1
Copyright @copyright{} 2006-2022 Antonio Diaz Diaz.

This manual is free documentation: you have unlimited permission to copy,
distribute, and modify it.
@end ifnottex


@node Introduction
@chapter Introduction
@cindex introduction

@uref{http://www.nongnu.org/arg-parser/arg_parser.html,,Arg_parser}
is an argument parser that follows POSIX and GNU conventions for
command line arguments. There exist C++ and C versions of Arg_parser. The
C++ version is implemented as a C++ class, while the C version is
implemented as a single struct plus associated functions. Both are simpler,
easier to use, and safer than @samp{getopt_long}.

For maximum stability, Arg_parser is self-contained. It extracts all the
information it needs from its arguments to avoid refering to them later.
This avoids index-out-of-bounds errors.

Arg_parser does not modify its arguments, nor uses any global variables. So
you may create more than one parser in your program if you need or want to.

The C++ version of Arg_parser can also parse options from configuration
files.

Arg_parser was developed as the argument parser for
@uref{http://www.gnu.org/software/moe/moe.html,,GNU moe}, because moe's
argument parsing is rather complex. Then I used it in my other projects,
including
@uref{http://www.gnu.org/software/ddrescue/ddrescue.html,,GNU ddrescue},
@uref{http://www.gnu.org/software/ed/ed.html,,GNU ed},
@uref{http://www.nongnu.org/lzip/lzip.html,,lzip},
@uref{http://www.gnu.org/software/ocrad/ocrad.html,,GNU ocrad},
@uref{http://www.nongnu.org/lzip/tarlz.html,,tarlz}, and
@uref{http://www.nongnu.org/zutils/zutils.html,,zutils}, with
excellent results.


@node Argument syntax
@chapter Syntax of command line arguments
@cindex argument syntax

POSIX recommends these conventions for command line arguments.
Arg_parser makes it easy to implement them.

@itemize @bullet
@item A command line argument is an option if it begins with a hyphen
delimiter (@samp{-}).

@item Multiple options may follow a hyphen delimiter in a single token
if the options don't take arguments. Thus, @samp{-abc} is equivalent to
@w{@samp{-a -b -c}}.

@item Option names are single alphanumeric characters.

@item Certain options require an argument.

@item An option and its argument may or may not appear as separate
tokens. (In other words, the whitespace separating them is optional).
Thus, @w{@samp{-o foo}} and @samp{-ofoo} are equivalent.

@item Options typically precede other non-option arguments.

Arg_parser normally makes it appear as if all the option arguments were
specified before all the non-option arguments for the purposes of parsing,
even if the user of your program intermixed option and non-option arguments.
If you want the arguments in the exact order the user typed them, call
@samp{Arg_parser} with @w{@var{in_order} = true}.

@item The argument @samp{--} terminates all options; any following arguments
are treated as non-option arguments, even if they begin with a hyphen.

@item A token consisting of a single hyphen character is interpreted as
an ordinary non-option argument. By convention, it is used to specify
input from or output to the standard input and output streams.

@item Options may be supplied in any order, or appear multiple times.
The interpretation is left up to the particular application program.

@item GNU adds @dfn{long options} to these conventions. Long options
consist of @samp{--} followed by a name made of alphanumeric characters
and hyphens. Option names are typically one to three words long, with
hyphens to separate words. Users can abbreviate the option names as long
as the abbreviations are unique.

@item A long option and its argument may or may not appear as separate
tokens. In the latter case they must be separated by an equal sign @samp{=}.
Thus, @w{@samp{--foo bar}} and @samp{--foo=bar} are equivalent.

@item The syntax for optional option arguments is
@samp{-<short_option><argument>} (without whitespace), or
@samp{--<long_option>=<argument>}.
@end itemize


@node Initialization
@chapter Parsing arguments and reporting errors
@cindex initialization

To use Arg_parser in your own programs first copy the files
@samp{arg_parser.h} and @samp{arg_parser.cc} in your source tree. See the
file @samp{main.cc} for an example of use.

The class @samp{Arg_parser} has two constructors; one to parse command line
arguments from @var{argv}, and the other to parse a single token from a
configuration file or other source.

@anchor{struct Option}
@deffn {Data Type} struct Option
This structure describes a single option for the sake of
@samp{Arg_parser}. The argument @var{options} must be an array of these
structures, one for each option. Terminate the array with an element
containing a code which is zero.

@samp{struct Option} has the following members:

@table @code
@item int code
This member is the code that identifies the option, normally the
short-option character. Must be different from 0. A code value outside
the unsigned char range means a long-only option.

@item const char * long_name
This member is the long option name. It is a zero-terminated string. A
null or empty long_name means a short-only option.

@item enum Has_arg has_arg
This member says whether the option takes an argument. It has three
valid values: @samp{no}, @samp{yes}, and @samp{maybe}.
@end table
@end deffn

@defun Arg_parser ( const int @var{argc}, const char * const @var{argv}[], const Option @var{options}[], const bool @var{in_order} = false )
Constructor. Reads the arguments in @var{argv} and parses all options,
option arguments, and non-option arguments contained in them. In case of
error, @samp{error().size()} will be non-zero.
@end defun

@defun Arg_parser ( const char * const @var{opt}, const char * const @var{arg}, const Option @var{options}[] )
Restricted constructor. Parses a single token (plus an optional second
token in case an argument is needed for an option parsed). Can be used to
parse options from a configuration file one at a time. Be warned that a
single token may produce an undefined number of short options. In case
of error, @samp{error().size()} will be non-zero.
@end defun

@deftypefun {const std::string &} error () const
Use this funtion to verify that the arguments have been correctly parsed
by the constructor. If there was an error parsing the arguments,
@samp{error} returns a non-empty error message explaining the cause.
@end deftypefun


@node Using Arg_parser
@chapter Using the class @samp{Arg_parser}
@cindex using Arg_parser

After a successful call to the constructor, which must be verified by
calling @samp{error}, the options and arguments parsed can be accessed
by means of the following functions:

@deftypefun int arguments () const
This function returns the number of options and non-option arguments parsed.
This number is usually different from argc.
@end deftypefun

@deftypefun int code ( const int @var{i} ) const
This function returns the code of the option at position @var{i}. Valid
values for @var{i} range from 0 to @w{@samp{arguments() - 1}}. If the
code returned is non-zero, @samp{argument(@var{i})} is the option's
argument (or is empty if the option does not have an argument). If the
code returned is zero, @samp{argument(@var{i})} is a non-option argument.
@end deftypefun

@deftypefun {const std::string &} parsed_name ( const int @var{i} ) const
This function returns the full name of the option parsed (short or long) at
position @var{i}. It may be useful to produce more accurate diagnostic
messages. For non-option arguments it returns the empty string.
@end deftypefun

@deftypefun {const std::string &} argument ( const int @var{i} ) const
This function returns the argument at position @var{i}. It may be the
argument of an option or a non-option argument, depending on the value
returned by @samp{code(@var{i})}. Valid values for @var{i} range from 0
to @w{@samp{arguments() - 1}}.
@end deftypefun


@node C version
@chapter Using the C version of Arg_parser
@cindex C version

To use the C version of Arg_parser in your own programs first copy the files
@samp{carg_parser.h} and @samp{carg_parser.c} in your source tree. See the
file @samp{cmain.c} for an example of use.

Then you need to declare a variable of type @samp{struct Arg_parser},
pass its address to @samp{ap_init} to initialize it, and verify that
@samp{ap_error} returns 0.

@samp{struct ap_Option} is identical to @samp{struct Option}, except
that @samp{Has_arg} becomes @samp{ap_Has_arg}, and the names of its
three values are also prefixed with @samp{ap_}. @xref{struct Option},
for details about the members.

@deftypefun char ap_init ( struct Arg_parser * const @var{ap}, const int @var{argc}, const char * const @var{argv}[], const struct ap_Option @var{options}[], const char @var{in_order} )
Reads the arguments in @var{argv} and parses all options, option
arguments, and non-option arguments contained in them. Returns 0 if there
is not enough memory, else 1. In case of error, @samp{ap_error} will
return a non-null pointer.
@end deftypefun

@deftypefun void ap_free ( struct Arg_parser * const @var{ap} )
Frees all dynamically allocated data structures.
@end deftypefun

@deftypefun {const char *} ap_error ( const struct Arg_parser * const @var{ap} )
Use this funtion to verify that the arguments have been correctly parsed
by @samp{ap_init}. If there was an error parsing the arguments,
@samp{ap_error} returns a pointer to an error message explaining the
cause, else it returns a null pointer.
@end deftypefun

After a successful call to @samp{ap_init}, which must be verified by
calling @samp{ap_error}, the options and arguments parsed can be accessed
by means of the following functions:

@deftypefun int ap_arguments ( const struct Arg_parser * const @var{ap} )
This function returns the number of options and non-option arguments parsed.
This number is usually different from argc.
@end deftypefun

@deftypefun int ap_code ( const struct Arg_parser * const @var{ap}, const int @var{i} )
This function returns the code of the option at position @var{i}. Valid
values for @var{i} range from 0 to @w{@samp{ap_arguments() - 1}}. If the
code returned is non-zero, @samp{ap_argument(@var{i})} is the option's
argument (or is empty if the option does not have an argument). If the
code returned is zero, @samp{ap_argument(@var{i})} is a non-option argument.
@end deftypefun

@deftypefun {const char *} ap_parsed_name ( const struct Arg_parser * const @var{ap}, const int @var{i} )
This function returns the full name of the option parsed (short or long) at
position @var{i}. It may be useful to produce more accurate diagnostic
messages. For non-option arguments it returns the empty string.
@end deftypefun

@deftypefun {const char *} ap_argument ( const struct Arg_parser * const @var{ap}, const int @var{i} )
This function returns the argument at position @var{i}. It may be the
argument of an option or a non-option argument, depending on the value
returned by @samp{ap_code(@var{i})}. Valid values for @var{i} range from 0
to @w{@samp{ap_arguments() - 1}}.
@end deftypefun

When you are finished, you should free all dynamically allocated data
structures by calling @samp{ap_free}.


@node Problems
@chapter Reporting bugs
@cindex bugs
@cindex getting help

There are probably bugs in Arg_parser. There are certainly errors and
omissions in this manual. If you report them, they will get fixed. If
you don't, no one will ever know about them and they will remain unfixed
for all eternity, if not longer.

If you find a bug in Arg_parser, please send electronic mail to
@email{arg-parser-bug@@nongnu.org}. Include the version number, which
you can find by running @w{@samp{arg_parser --version}}.


@node Concept index
@unnumbered Concept index

@printindex cp

@bye