Arg< T > Class Template Reference

#include <Pt/Arg.h>

Read and extract command-line options. More...

Inherits ArgBaseT< T >.

Public Member Functions
	Arg (const T &def=T())
	Constructor with initial value.
	Arg (int &argc, char *argv[], char ch, const T &def=T())
	Extract short option. More...
	Arg (int &argc, char *argv[], const char *str, const T &def=T())
	Extract long option. More...
	Arg (int &argc, char *argv[])
	Extracts the next parameter.
const T &	get () const
	Returns the value.
bool	isSet () const
	Returns true if the option is set, false if default is used.
bool	set (int &argc, char *argv[], char ch)
	Extract short option. More...
bool	set (int &argc, char *argv[], const char *str)
	Extract long option. More...
bool	set (int &argc, char *argv[])
	Reads next parameter and removes it.

Related Functions
template<typename T >
std::ostream &	operator<< (std::ostream &out, const Arg< T > &arg)
	Write Arg to an std::ostream.

Detailed Description

template<typename T>
class Pt::Arg< T >

Arg objects can be used to process command line options passed to the main function of the program. A syntax for short-named and long-named options is supported. Short-named options start with a single hypen followd by a character (-O). Optionally, a value follows directly (-Ofoo) or separated by whitespace(-O foo). Alternatively, option names can be consist of any character sequence to support unix style options(–option) and windows style options (/OPTION). An optional value follows either separated by whitespace (–option yes) or an equal character (/OPTION=yes). Note that constructing an Arg from with the character 'n' or with the string "-n" are equivalent.

The template parameter of the Arg class is the argument value type, which must be streamable, i.e. the operator >> (std::istream&, T&) must be defined for the type T. When an Arg is constructed, the operator will be used to extract the value from the command-line string. the next example demonstrates this:

int main(int argc, char* argv[])
{
    Pt::Arg<int> option_n(argc, argv, 'n', 0);
    std::cout << "value for -n: " << option_n << endl;
}

Options are removed from the option-list, so programs can easily check, if there are parameters left, after all options were extracted. A specialization exists for boolean parameters. This implements a switch, which is on, if the option is present and off, if it is missing. The option consists, in this case, only of a command line flag without a value. Boolean parameters can also be grouped, so -abc is processed like -a -b -c.

Pt::Arg<bool> debug(argc, argv, "--debug");
if (debug)
    std::cout << "debug flag is set" << std::endl;

The example shown above not only shows a boolean parameter, but also how long-named options are handled, in this case "--debug".

Constructor & Destructor Documentation

Arg	(	int &	argc,
		char *	argv[],
		char	ch,
		const T &	def = T()
	)

Parameters

argc	1. parameter of main
argv	2. of main
ch	optioncharacter
def	default-value

Example:

Pt::Arg<unsigned> offset(argc, argv, 'o', 0);
unsigned value = offset.getValue();

Arg	(	int &	argc,
		char *	argv[],
		const char *	str,
		const T &	def = T()
	)

Long option names starting with "--". This (and more) is supported here. Instead of giving a single option-character, you specify a string.

Example:

Pt::Arg<int> option_number(argc, argv, "--number", 0);
std::cout << "number =" << option_number.getValue() << std::endl;

Member Function Documentation

bool set	(	int &	argc,
		char *	argv[],
		char	ch
	)

Parameters

argc	1. parameter of main
argv	2. of main
ch	optioncharacter

Example:

Pt::Arg<unsigned> offset;
offset.set(argc, argv, 'o');
unsigned value = offset.getValue();

bool set	(	int &	argc,
		char *	argv[],
		const char *	str
	)

GNU defines long options starting with "--". This (and more) is supported here. Instead of giving a single option-character, you specify a string.

Example:

Pt::Arg<int> option_number;
number.set(argc, argv, "--number");
std::cout << "number =" << option_number.getValue() << std::endl;