# FBB::ArgConfig(3bobcat)

## Program Arguments
(libbobcat-dev_5.07.03)

## 2005-2021

## NAME

FBB::ArgConfig - A singleton class processing program arguments

## SYNOPSIS

#include <bobcat/argconfig>
Linking option: -lbobcat

## DESCRIPTION

Singleton class (see Gamma et al., 1995) built around getopt(3) and getopt_long(3). The class handles short- and long command-line options as well as configuration files.

In addition to the standard command-line options, configuration files containing long options as their keys, optionally followed by a colon are also recognized by the various option members. E.g., an option --input filename can be specified in the configuration file like

    input: filename

or

    input filename

Options without arguments should probably not use the colon, although it is accepted by ConfigArg. E.g., for the option --verbose both forms are OK:

    verbose
    verbose:

## NAMESPACE

FBB
All constructors, members, operators and manipulators, mentioned in this man-page, are defined in the namespace FBB.

## INHERITS FROM

FBB::Arg,
FBB::ConfigFile

## CONSTRUCTORS

Since the class is a Singleton, no public constructors are available. Instead, static members are offered to initialize and access the single ArgConfig object. See below.

## STATIC MEMBERS

- FBB::ArgConfig &initialize(char const *optstring, int argc, char **argv, [std::string const &fname,] Comment cType = KeepComment, SearchCasing sType = SearchCaseSensitive, Indices iType = IgnoreIndices):
  Initializes the FBB::ArgConfig singleton. Must be called only once. Throws an FBB::Exception exception if called repeatedly or if called with argv not containing a defined option (which is shown by the FBB::Exception's what member). The fname argument is optional. If provided, a configuration file by the specified name is opened (and must exist); if omitted the ArgConfig is created without using a configuration file. In the latter case a configuration file may be specified later using the open member inherited from ConfigFile. The final three parameters are ConfigFile parameters, receiving the shown default values. This constructor returns a reference to the singleton object, allowing code initializing ArgConfig to use the initialized object immediately.

- FBB::ArgConfig &initialize(char const *optstring, LongOption const * const begin, LongOption const * const end, int argc, char **argv, [std::string const &fname,] Comment cType = KeepComment, SearchCasing sType = SearchCaseSensitive, Indices iType = IgnoreIndices):
  Initializes the FBB::ArgConfig singleton. Accepts two iterators of an array of Arg::LongOption objects, holding long-options. Must be called only once. Throws an FBB::Exception exception if called repeatedly or if called with argv not containing a defined option (which is shown by the FBB::Exception's what member). Refer to arg(3bobcat) for the description of Arg::LongOption. The constructor's final six parameters are identical to the previous constructor's final six arguments. This constructor returns a reference to the singleton object, allowing code initializing ArgConfig to use the initialized object immediately.

  The argument optstring should consist of letters, possibly postfixed by:

  - a colon (:), indicating that the option has a required argument;
  - a double colon (::), indicating that the option itself has an optional argument (in that case, the option's value will be empty, unless specified).
- FBB::ArgConfig &instance():
  Returns the instance of the ArgConfig object, available after calling one of the ArgConfig::initialize members. If called before initialization, an FBB::Exception exception is thrown.

## NON-STATIC MEMBER FUNCTIONS

All public members of the Arg and ConfigFile classes are also offered by the ArgConfig class. As several option members were reimplemented by this class all option members are discussed below. All other members inherit straight from the classes Arg and ConfigFile. Consult their man pages for details.

- size_t option(int option) const:
  Returns the number of times `option' (or its long option synonym, if defined) was specified as command line option or as as a configuration file option.
- size_t option(std::string const &options) const:
  Returns the total number of times any of the characters specified in the `options' string (or their long option synonyms) was specified as command line option or as as a configuration file option.
- size_t option(string *value, int option) const:
  Returns the number of times the provided option (or its long option synonym) was present as either a command line option or as a configuration file option. If the return value is non-zero then the value of the first occurrence of this option (first checking the command line options; then checking the configuration file) is stored in *value, which is left untouched if `option' was not present. 0 may be specified for value if the option does not have a value or if the value should not be stored.
- size_t option(size_t idx, string *value, int option) const:
  This member acts identically to the Arg::option member having the identical prototype. It does not consider the configuration file but merely returns the number of times the provided option (or its long option synonym) was present. If the return value is non-zero then the value of the idxth occurrence (0-based offset) of this option is stored in *value, which is left untouched if `option' was not present or if idx is or exceeds the number of specifications of the provided option. 0 may be specified for value if the option does not have a value or if the value should not be stored.
- size_t option(size_t *idx, string *value, int option) const:
  This member acts identically to the Arg::option member having the identical prototype. It does not consider the configuration file but merely returns the number of times the provided option (or its long option synonym) was present. If the return value is non-zero then the offset (within the series of option specifications) of the first option having a non-empty option value is returned in *idx, while its option value is stored in *value. Both *value and *idx are left untouched if `option' was not present. 0 may be specified for value if the option does not have a value or if the value should not be stored.
- size_t option(string *value, char const *longOption) const:
  Returns the number of times the specified long option (not having a single-character synonym) was present as either a command line option or in the configuration file. If found, then the value found at the first occurrence of the option (first considering the command line options, then the configuration file) is stored in *value. The string pointed to by value is left untouched if the long option was not present. 0 may be specified for value if the option does not have a value or if the value should not be stored.
- size_t option(size_t idx, string *value, char const * longOption) const:
  This member acts identically to the Arg::option member having the identical prototype. It does not consider the configuration file but merely returns the number of times the provided long option (not having a single-character synonym) was present. If the return value is non-zero then the value of the idxth occurrence (0-based offset) of this long option is stored in *value, which is left untouched if the long option was not present or if idx is or exceeds the number of specifications of the provided long option. 0 may be specified for value if the long option does not have a value or if the value should not be stored.
- size_t option(size_t *idx, string *value, int longOption) const:
  This member acts identically to the Arg::option member having the identical prototype. It does not consider the configuration file but merely returns the number of times the provided long option (not having a single-character synonym) was present. If the return value is non-zero then the offset (within the series of this long option specifications) of the first long option having a non-empty option value is returned in *idx, while its option value is stored in *value. Both *value and *idx are left untouched if long option was not present. 0 may be specified for value if the long option does not have a value or if the value should not be stored.

## EXAMPLE

    #include <iostream>
    #include <string>

    #include <bobcat/argconfig>
    #include <bobcat/exception>

    using namespace std;
    using namespace FBB;

    ArgConfig::LongOption lo[] =
    {
        ArgConfig::LongOption{"option", 'o'},
        ArgConfig::LongOption{"value-option", 'v'}
    };

    class X
    {
        ArgConfig &d_arg;

        public:
            X();
            void function();
    };

    X::X()
    :
        d_arg(ArgConfig::instance())
    {}

    void X::function()
    {
        if (d_arg.nArgs() == 0)
            throw Exception() << "Provide the name of a config file as 1st arg";

        cout << "Counting " << d_arg.option('o') << " instances of -o or "
                                                                "--option\n";

        d_arg.open(d_arg[0]);       // Now open the config file explicitly
                                // (alternatively: use a constructor expecting
                                // a file name)

        cout << "Counting " << d_arg.option('o') << " instances of -o or "
                                                                "--option\n";

        string optval;
        size_t count = d_arg.option(&optval, 'v');

        cout << "Counting " << count <<
                            " instances of -v or --value-option\n";
        if (count)
            cout << "Option value = " << optval << endl;
    }

    int main(int argc, char **argv)
    try
    {
        ArgConfig::initialize("ov:", lo, lo + 2, argc, argv);

        X x;
        x.function();
    }
    catch (Exception const &err)
    {
        cout << "Terminating " << err.what() << endl;
        return 1;
    }

## FILES

bobcat/argconfig - defines the class interface

## SEE ALSO

arg(3bobcat), configfile(3obcat), bobcat(7)

## BUGS

None Reported.

## BOBCAT PROJECT FILES

- https://fbb-git.gitlab.io/bobcat/: gitlab project page;
- bobcat_5.07.03-x.dsc: detached signature;
- bobcat_5.07.03-x.tar.gz: source archive;
- bobcat_5.07.03-x_i386.changes: change log;
- libbobcat1_5.07.03-x_*.deb: debian package containing the libraries;
- libbobcat1-dev_5.07.03-x_*.deb: debian package containing the libraries, headers and manual pages;

## BOBCAT

Bobcat is an acronym of `Brokken's Own Base Classes And Templates'.

## COPYRIGHT

This is free software, distributed under the terms of the GNU General Public License (GPL).

## AUTHOR

Frank B. Brokken (f.b.brokken@rug.nl).