FBB::Arg(3bobcat)

Command Line Arguments
(libbobcat-dev_4.08.03-x.tar.gz)

2005-2018

NAME

FBB::Arg - A singleton class interfacing command line arguments

SYNOPSIS

#include <bobcat/arg>
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,

NAMESPACE

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

INHERITS FROM

ENUMERATION

The FBB::Arg::Type enumeration is defined by the FBB::Arg class. It has the following values intended for public use: None, Required, Optional. These values are used when constructing objects of the nested class FBB::Arg::LongOption, see below.

CONSTRUCTORS

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

STATIC MEMBERS

FBB::Arg &initialize(char const *optstring, int argc, char **argv):
Initializes the FBB::Arg 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). Returns a reference to the singleton object, allowing code initializing Arg to use the initialized object immediately.
FBB::Arg &initialize(char const *optstring, LongOption const * const begin, LongOption const * const end, int argc, char **argv):
Initializes the FBB::Arg 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). See the description of Arg::LongOption below. Returns a reference to the singleton object, allowing code initializing Arg to use the initialized object immediately.
optstring should consist of letters, possibly postfixed by:
- a colon (:), indicating that the option requires an option value.
- a double colon (::), indicating that the option itself has an optional argument. With short options the option value is considered absent unless it immediately follows the short option (e.g., -tvalue for a short option -t). Long options optionally accepting arguments should always immediately be followed by a = character. Here the option's value must immediately follow the = character, and must start with a non-blank character, or the option's value is considered absent. E.g., --value= indicates an absent option value, --value=text indicates the option's value equals text. If an option value itself contains blanks, it should be surrounded by single or double quotes (e.g., -t'this value', or --text='this value'). The surrounding quotes themselves are not part of the option's value.
FBB::Arg &instance():
Returns the instance of the Arg object, available after calling one of the Arg::initialize() members. If called before initialization, an FBB::Exception exception is thrown.

OVERLOADED OPERATOR

char const *operator[](size_t idx) const:
Returns argument[idx], after having removed all specified options. 0 is returned if no arg[x] is available. The program name (argv[0]) is NOT counted here: index 0 refers to the first ARGUMENT, e.g., the program's argv[1].

NON-STATIC MEMBER FUNCTIONS

char const **argPointers():
Returns argv-like set of pointers to all remaining arguments. The last element is guaranteed to be a 0-pointer. The first nArg() elements point to the respective C-string values of the arguments.
std::string const &basename() const:
Returns the program's basename.
size_t beyondDashes() const:
Returns the index of the first argument after a -- argument or nArgs() if no -- argument was encountered.
A -- argument ends Arg's argument processing, and all arguments beyond the first -- argument are kept `as is'. The beyondDashes member returns the index of the first argument beyond the -- argument, which itself is removed from the remaining set of arguments.
void help() const:
If the member versionHelp (see below) has been called then this member calls the usage function that was passed to versionHelp. If versionHelp has not been called (i.e., if no usage function has been specified) then an exception is thrown.
size_t nArgs() const:
Returns the number of arguments left after option-removal. The program name argv[0] is NOT counted here.
size_t nLongOptions() const:
Returns the number of long options for which no short option synonym exist. If long options are multiply specified, then each specification is counted.
size_t nOptions() const:
Returns the number of specified single character options. If short options have long option synonyms, then these long option synonyms are counted as if they were specified as single character options. If single character options (or their long option synonyms) are multiply specified, then each specification is counted.
size_t option(int option) const:
The number of times `option' (or its long option synonym, if defined) was specified is returned.
size_t option(std::string const &options) const:
The number of times one of the options specified in the `option' argument (or their long option synonyms) were present is returned.
size_t option(string *value, int option) const:
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 first occurrence of this option 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:
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:
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. Its value is then stored in *value, which 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:
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:
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.
void versionHelp(void (*usage)(std::string const &progname), char const *version, size_t minArgs, int helpFlag = 'h', int versionFlag = 'v') const:
If versionFlag was specified, and the helpFlag was not specified the program's name (using basename()) and version is displayed to std::cout. Otherwise, if the helpFlag was provided or if there are fewer arguments than minArgs usage() is called with argument basename(). If either version- or help information is shown, the int value 1 is thrown as an exception.
Note that versionhelp compares minArgs against nArgs. If minArgs should be compaired against the number of arguments up to a possible `--' argument (i.e., beyondDashes' return value), then add nArgs() - beyondDashes() to the minArg argument. E.g.,
```
    arg.versionHelp(usage, version, 2 + arg.nArgs() - arg.beyondDashes());
            
```
The address of the usage() function, the current version and the minimum number of arguments must be specified. Default argument values are provided for the option flags.

THE NESTED CLASS FBB::Arg::LongOption

Long options are defined using objects of the nested class FBB::Arg::LongOption. This class offers the following constructors:

FBB::Arg::LongOption(char const *name, FBB::Arg::Type type = None):
This constructor is used to define a long option for which no corresponding short option is defined. The parameter name is the name of the long option (without prefixing the -- characters, which are required when specifying the long option).
FBB::Arg::LongOption(char const *name, int optionChar):
This constructor is used to define a long option for which a corresponding short option is defined. The parameter name is the name of the long option (without prefixing the -- characters, which are required when specifying the long option).

In a program, long options may be specified as follows:

First, construct an array
```
    FBB::Arg::LongOption longOptions[] = { c1, c2, ... cn }
        
```
Where c1, c2, ..., cn are n constructor invocations of FBB::Arg::LongOption() constructors
Next, pass longOptions, LongOptions + n as 2nd and 3rd arguments to initialize()

EXAMPLE

The following example illustrates defining long options and shows an initialization. It is not a full-fledched example in the sense of a small runnable program.


#include <bobcat/arg>

using namespace FBB;

namespace   // the anonymous namespace can be used here
{
    Arg::LongOption longOptions[] = 
    {
        Arg::LongOption{"debug"},
        Arg::LongOption{"filenames", 'f'},
        Arg::LongOption{"help", 'h'},
        Arg::LongOption{"version", 'v'},
    };
    auto longEnd = longOptions + sizeof(longOptions) / sizeof(longOptions[0]);
}

int main(int argc, char **argv)
try
{
    Arg &arg = Arg::initialize("df:hv", 
                    longOptions, longEnd, argc, argv);

    // code using arg, etc.
}
catch(Exception const &err)     // handle exceptions
{
    cerr << err.what() << endl;
    return err.which();
}
catch(int x)
{
    return x;
}

FILES

bobcat/arg - defines the class interface

BUGS

None Reported.

DISTRIBUTION FILES

bobcat_4.08.03-x.dsc: detached signature;
bobcat_4.08.03-x.tar.gz: source archive;
bobcat_4.08.03-x_i386.changes: change log;
libbobcat1_4.08.03-x_*.deb: debian package holding the libraries;
libbobcat1-dev_4.08.03-x_*.deb: debian package holding the libraries, headers and manual pages;
http://sourceforge.net/projects/bobcat: public archive location;

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).