TCLAP has a few key classes to be aware of. The first is the CmdLine (command line) class. This class parses the command line passed to it according to the arguments that it contains. Arguments are separate objects that are added to the CmdLine object one at a time. The six argument classes are: ValueArg, UnlabeledValueArg, SwitchArg, MultiSwitchArg, MultiArg and UnlabeledMultiArg. These classes are templatized, which means they can be defined to parse a value of any type. Once you add the arguments to the CmdLine object, it parses the command line and assigns the data it finds to the specific argument objects it contains. Your program accesses the values parsed by calls to the getValue() methods of the argument objects.

Here is a simple example ...

#include <string>
#include <iostream>
#include <algorithm>
#include <tclap/CmdLine.h>

int main(int argc, char** argv)
{

	// Wrap everything in a try block.  Do this every time, 
	// because exceptions will be thrown for problems.
	try {  

	// Define the command line object, and insert a message
	// that describes the program. The "Command description message" 
	// is printed last in the help text. The second argument is the 
	// delimiter (usually space) and the last one is the version number. 
	// The CmdLine object parses the argv array based on the Arg objects
	// that it contains. 
	TCLAP::CmdLine cmd("Command description message", ' ', "0.9");

	// Define a value argument and add it to the command line.
	// A value arg defines a flag and a type of value that it expects,
	// such as "-n Bishop".
	TCLAP::ValueArg<std::string> nameArg("n","name","Name to print",true,"homer","string");

	// Add the argument nameArg to the CmdLine object. The CmdLine object
	// uses this Arg to parse the command line.
	cmd.add( nameArg );

	// Define a switch and add it to the command line.
	// A switch arg is a boolean argument and only defines a flag that
	// indicates true or false.  In this example the SwitchArg adds itself
	// to the CmdLine object as part of the constructor.  This eliminates
	// the need to call the cmd.add() method.  All args have support in
	// their constructors to add themselves directly to the CmdLine object.
	// It doesn't matter which idiom you choose, they accomplish the same thing.
	TCLAP::SwitchArg reverseSwitch("r","reverse","Print name backwards", cmd, false);

	// Parse the argv array.
	cmd.parse( argc, argv );

	// Get the value parsed by each arg. 
	std::string name = nameArg.getValue();
	bool reverseName = reverseSwitch.getValue();

	// Do what you intend. 
	if ( reverseName )
	{
		std::reverse(name.begin(),name.end());
		std::cout << "My name (spelled backwards) is: " << name << std::endl;
	}
	else
		std::cout << "My name is: " << name << std::endl;


	} catch (TCLAP::ArgException &e)  // catch exceptions
	{ std::cerr << "error: " << e.error() << " for arg " << e.argId() << std::endl; }
}

The output should look like:

% test1 -n mike
My name is: mike

% test1 -n mike -r
My name (spelled backwards) is: ekim

% test1 -r -n mike
My name (spelled backwards) is: ekim

% test1 -r
PARSE ERROR:
             One or more required arguments missing!

Brief USAGE:
   test1  [-r] -n <string> [--] [-v] [-h]

For complete USAGE and HELP type:
   test1 --help


% test1 --help

USAGE:

   test1  [-r] -n <string> [--] [-v] [-h]


Where:

   -r,  --reverse
     Print name backwards

   -n <string>  --name <string>
     (required)  (value required)  Name to print

   --,  --ignore_rest
     Ignores the rest of the labeled arguments following this flag.

   -v,  --version
     Displays version information and exits.

   -h,  --help
     Displays usage information and exits.


   Command description message

Each CmdLine owns its delimiter and positional registration checks. Optional positional arguments must be registered last; constructing an unregistered argument does not affect another parser. Use separate argument objects for separate parsers and keep the parser alive while using its registered arguments. Custom argument implementations should use getDelimiter(), which observes their parser's delimiter. The legacy static Arg::delimiter() and Arg::setDelimiter() remain available for unregistered arguments and legacy custom code, but do not select a registered parser's delimiter. The legacy OptionalUnlabeledTracker static helper is no longer used by the built-in arguments.

Failed registration leaves the parser's argument list, required count, positional checks, delimiter bindings and group membership unchanged. A group rejected during attachment can be retried on another parser. Custom addToList() hooks receive a temporary list with the owning delimiter already bound; do not retain that list or re-enter registration. Application side effects in custom hooks are not rolled back. Custom CmdLineInterface implementations retain the legacy attachment default and can override the protected attachGroup() hook for their own transaction handling.

add() borrows its argument; it does not copy it or transfer ownership. Keep caller-owned arguments alive while the parser uses them. Constraints and custom output objects passed to setOutput() are also borrowed and must remain alive while used. Declare dependencies before the objects that refer to them. This example declares the constraint and output first, the argument next, and the parser last, so destruction happens in the reverse order:

#include <tclap/CmdLine.h>
#include <tclap/ValuesConstraint.h>
#include <tclap/StdOutput.h>
#include <vector>

int main(int argc, char **argv) {
    std::vector<int> allowed;
    allowed.push_back(1);
    allowed.push_back(2);
    TCLAP::ValuesConstraint<int> choices(allowed);
    TCLAP::StdOutput output;
    TCLAP::ValueArg<int> count("n", "number", "Choose a number",
                              false, 1, &choices);
    TCLAP::CmdLine cmd("example");
    cmd.setOutput(&output);
    cmd.add(count);
    cmd.parse(argc, argv);
    return 0;
}

Visitor objects supplied to arguments are borrowed and must remain alive when invoked. Groups passed to the parser are also borrowed. Use distinct argument objects for separate live parsers. Keep the parser alive while using registered arguments' delimiter bindings.

An attached delimiter can carry an empty value, for example --name= when the parser delimiter is =. With the default space delimiter, pass an empty argv element (for example, --name "" in a shell). Strings and types with StringLike traits receive the empty string directly. Numeric values reject empty input. Custom stream extractors decide whether empty input is valid through their operator>> implementation; no default-value substitution is performed. Constraints still check explicitly supplied values, including empty strings. These rules apply to both ValueArg and MultiArg. Omitting a value entirely is still an error.

For installed CMake consumers, use find_package(TCLAP CONFIG REQUIRED) and link your application target with target_link_libraries(app PRIVATE TCLAP::TCLAP). Use CMAKE_PREFIX_PATH for a custom installation prefix, or TCLAP_DIR for a nonstandard package metadata directory. See INSTALL in the source root for a complete example. The imported target propagates the C++20 language requirement.

TCLAP is implemented entirely in header files which means you only need to include CmdLine.h to use the library.

        #include <tclap/CmdLine.h>

You'll need to make sure that your compiler can see the header files. If you do the usual "make install" then your compiler should see the files by default. Alternatively, you can use the -I complier argument to specify the exact location of the libraries.

        c++ -std=c++20 -o my_program -I /some/place/tclap-1.6/include my_program.cpp

Where /some/place/tclap-1.6 is the place you have unpacked the distribution.

Finally, if you want to include TCLAP as part of your software (which is perfectly OK, even encouraged) then simply copy the contents of /some/place/tclap-1.6/include (the tclap directory and all of the header files it contains) into your include directory. The necessary m4 macros for proper configuration are included in the config directory.

TCLAP 1.6 requires a C++20 compiler and a C++20 standard library that provides std::format. It retains the 1.4-style API while using C++20 internally. For C++98 projects, use TCLAP 1.4. TCLAP 1.2 remains available for existing integrations that require its legacy API and behavior.

The CmdLine class contains the arguments that define the command line and manages the parsing of the command line. The CmdLine doesn't parse the command line itself it only manages the parsing. The actual parsing of individual arguments occurs within the arguments themselves. The CmdLine keeps track of of the required arguments, relationships between arguments, and output generation.

SwitchArgs are what the name implies: simple, on/off, boolean switches. Use SwitchArgs anytime you want to turn some sort of system property on or off. SwitchArgs don't parse a value. They return TRUE or FALSE, depending on whether the switch has been found on the command line and what the default value was defined as.

ValueArgs are arguments that read a value of some type from the command line. Any time you need a file name, a number, etc. use a ValueArg or one of its variants. All ValueArgs are templatized and will attempt to parse the string its flag matches on the command line as the type it is specified as. ValueArg<int> will attempt to parse an int, ValueArg<float> will attempt to parse a float, etc. If operator>> for the specified type doesn't recognize the string on the command line as its defined type, then an exception will be thrown.

A MultiArg is a ValueArg that can be specified more than once on a command line and instead of returning a single value, returns a vector of values.

Imagine a compiler that allows you to specify multiple directories to search for libraries...

                % fooCompiler -L /dir/num1 -L /dir/num2 file.foo 

Exceptions will occur if you try to do this with a ValueArg or a SwitchArg. In situations like this, you will want to use a MultiArg. A MultiArg is essentially a ValueArg that appends any value that it matches and parses onto a vector of values. When the getValue() method is called, a vector of values, instead of a single value is returned. A MultiArg is declared much like a ValueArg:

                MultiArg<int> itest("i", "intTest", "multi int test", false,"int" );
                cmd.add( itest );

Note that MultiArgs can be added to the CmdLine in any order (unlike UnlabeledMultiArg).

A MultiSwitchArg is a SwitchArg that can be specified more than once on a command line. This can be useful when command lines are constructed automatically from within other applications or when a switch occurring more than once indicates a value (-V means a little verbose -V -V -V means a lot verbose), You can use a MultiSwitchArg. The call to getValue() for a MultiSwitchArg returns the number (int) of times the switch has been found on the command line in addition to the default value. Here is an example using the default initial value of 0:

	MultiSwitchArg quiet("q","quiet","Reduce the volume of output");
	cmd.add( quiet );

Alternatively, you can specify your own initial value:

	MultiSwitchArg quiet("q","quiet","Reduce the volume of output",5);
	cmd.add( quiet );

An UnlabeledValueArg is a ValueArg that is not identified by a flag on the command line. Instead UnlabeledValueArgs are identified by their position in the argv array.

To this point all of our arguments have had labels (flags) identifying them on the command line, but there are some situations where flags are burdensome and not worth the effort. One example might be if you want to implement a magical command we'll call copy. All copy does is copy the file specified in the first argument to the file specified in the second argument. We can do this using UnlabeledValueArgs which are pretty much just ValueArgs without the flag specified, which tells the CmdLine object to treat them accordingly. The code would look like this:

                UnlabeledValueArg<float>  nolabel( "name", "unlabeled test", true, 3.14,
                                                  "nameString"  );
                cmd.add( nolabel );

Everything else is handled identically to what is seen above. The only difference to be aware of, and this is important: the order that UnlabeledValueArgs are added to the CmdLine is the order that they will be parsed!!!! This is not the case for normal SwitchArgs and ValueArgs. What happens internally is the first argument that the CmdLine doesn't recognize is assumed to be the first UnlabeledValueArg and parses it as such. Note that you are allowed to intersperse labeled args (SwitchArgs and ValueArgs) in between UnlabeledValueArgs (either on the command line or in the declaration), but the UnlabeledValueArgs will still be parsed in the order they are added. Just remember that order is important for unlabeled arguments.

An UnlabeledMultiArg is an UnlabeledValueArg that allows more than one value to be specified. Only one UnlabeledMultiArg can be specified per command line. The UnlabeledMultiArg simply reads the remaining unmatched operand values through the end of argv, including values after -- with its normal non-ignoreable setting. The marker itself is consumed by the parser. See end option recognition for the ignoreable policy and branch-specific limitations.

Say you want a strange command that searches each file specified for a given string (let's call it grep), but you don't want to have to type in all of the file names or write a script to do it for you. Say,

                % grep pattern *.txt

First remember that the * is handled by the shell and expanded accordingly, so what the program grep sees is really something like:

                % grep pattern file1.txt file2.txt fileZ.txt

To handle situations where multiple, unlabeled arguments are needed, we provide the UnlabeledMultiArg. UnlabeledMultiArgs take an explicit required constructor boolean; there is no default for that choice. With true, at least one operand must be supplied or parsing fails. With false, omission is allowed and getValue() returns an empty vector. The example below chooses false. The most important thing to remember is, that like UnlabeledValueArgs: order matters! In fact, an UnlabeledMultiArg must be the last argument added to the CmdLine!. Here is what a declaration looks like:

                //
                // UnlabeledMultiArg must be the LAST argument added!
                //
                UnlabeledMultiArg<string> multi("fileNames", "file names", false, "string");
                cmd.add( multi );
                cmd.parse(argc, argv);

                vector<string>  fileNames = multi.getValue();

You must only ever specify one (1) UnlabeledMultiArg. One UnlabeledMultiArg will read every unlabeled Arg that wasn't already processed by a UnlabeledValueArg into a vector of type T. Any UnlabeledValueArg or other UnlabeledMultiArg specified after the first UnlabeledMultiArg will be ignored, and if they are required, exceptions will be thrown. When you call the getValue() method of the UnlabeledValueArg argument, a vector will be returned. If you can imagine a situation where there will be multiple args of multiple types (stings, ints, floats, etc.) then just declare the UnlabeledMultiArg as type string and parse the different values yourself or use several UnlabeledValueArgs.

Multiple SwitchArgs can be combined into a single argument on the command line. If you have switches -a, -b and -c it is valid to do either:

                % command -a -b -c

or

                % command -abc

or

                % command -ba -c

This is to make this library more in line with the POSIX and GNU standards (as I understand them).

Suppose you have a command that must read input from one of two possible locations, either a local file or a URL. The command must read something, so one argument is required, but not both, yet neither argument is strictly necessary by itself. TCLAP can automatically enforce such constraints on a set of arguments using an argument group of type OneOf.

        ValueArg<string>  fileArg("f","file","File name to read",false,"/dev/zero", "filename");
        ValueArg<string>  urlArg("u","url","URL to load",false, "http://example.com", "URL");

        OneOf input;
        input.add(fileArg).add(urlArg);
        cmd.add(input);
        cmd.parse(argc, argv);

If the Arg has been matched on the command line, the isSet() will return TRUE.

        if ( fileArg.isSet() )
                readFile( fileArg.getValue() );
        else if ( urlArg.isSet() )
                readURL( urlArg.getValue() );
        else
                // Should never get here because TCLAP will note that one of the
                // required args above has not been set.
                throw("Very bad things...");

It is helpful to note that Args of any type can be part of the same argument group This means that you can add a SwitchArg and a ValueArg. This is helpful in situations where one of several options is necessary and one of the options requires additional information.

There is also the class EitherOf that works the same way, except it does not require any argument to be set. This can be useful if there is a natural default. For example, selecting the encryption algorithm may default to AES, but there may be flags for choosing another algorithm and they are all mutually exclusive.

AnyOf groups arguments for presentation only. It does not require a member to be selected or make one member depend on another. Each argument's own requirements still apply; check any conditional dependencies in application code after a successful parse.

Some commands have so many options that single flags no longer map sensibly to the available options. In this case, it is desirable to specify Args using only long options. This one is easy to accomplish, just make the flag value blank in the Arg constructor. This will tell the Arg that only the long option should be matched and will force users to specify the long option on the command line. The help output is updated accordingly.

        ValueArg<string>  fileArg("","file","File name",true,"homer","filename");

        SwitchArg  caseSwitch("","upperCase","Print in upper case",false);

Each argument name must be unique within a parser, including names of positional arguments. Nonempty short flags must also be unique. Short flags and long names are separate namespaces: one argument can use -x while another uses --x. Registering the same argument object twice is rejected. Descriptions are presentation text and may be identical or empty without causing a conflict.

These checks also apply when adding arguments to groups and attaching groups to a parser. They do not change the separate rules for positional ordering or exclusive groups. Failed registration leaves the parser and group membership unchanged.

Use arg.conflictsWith(other) to check for conflicting declarations, or compare addresses to check whether two references identify the same object. The legacy virtual equality operator is retained for source compatibility, including its positional description comparisons, but no longer controls registration or exclusive group selection. The conflict rule is nonvirtual and applies to custom arguments through their declared names and flags; additional tokens recognized by a custom processArg() are not inferred by registration. Custom equality overrides that previously changed duplicate detection must adapt to this declared-name-and-flag rule.

Stream-extracted values (ValueLike) reject embedded NUL bytes by default. This includes numeric, boolean and character values, and custom types using operator>>. For example, an integer token containing the bytes 42\0junk is rejected instead of being silently read as 42. This matters when supplying std::string tokens through the vector parsing overload; ordinary C-string command-line arguments cannot carry embedded NUL bytes.

To retain the historical behavior, define TCLAP_ALLOW_NUL_TRUNCATION=1 before including any TCLAP headers. The default is 0. Compatibility mode passes only the prefix before the first NUL to the extractor; it does not accept ordinary trailing junk such as 42junk. For CMake consumers:

        target_compile_definitions(myapp PRIVATE TCLAP_ALLOW_NUL_TRUNCATION=1)

Use the same setting across every translation unit in the program, including libraries that include TCLAP, because it changes header-defined template behavior. StringLike values, including std::string, preserve all bytes under either setting.

Check the result of the entire parse before using any argument values for application work. Parsing is not transactional: an error may leave earlier arguments changed, or even store a value that subsequently fails its constraint. isSet() does not restore old values and cannot substitute for checking the whole parse.

To parse again, call reset() and supply fresh input. The vector overload expects the program name at element 0 and erases that element. Reset restores parser/argument state, not the caller's input vector. Combined switches may also modify characters in that vector.

By default the parser reports input errors and exits. For recovery in an embedding application, use setExceptionHandling(false) and catch ArgException around the entire parse. With automatic help/version enabled, their visitors throw ExitException; handle that requested exit separately and stop normal application work. The following example disables those visitors to focus on error recovery.

#include <tclap/CmdLine.h>
#include <iostream>
#include <string>
#include <vector>

int main() {
    TCLAP::CmdLine cmd("reuse example", ' ', "1", false);
    cmd.setExceptionHandling(false);
    TCLAP::ValueArg<int> number("n", "number", "number", false, 0, "integer");
    cmd.add(number);
    std::vector<std::string> first{"prog", "-n", "7", "--bogus"};
    try {
        cmd.parse(first);
        return 1; // This input should fail.
    } catch (const TCLAP::ArgException &) {
        // A failure may leave number changed. Do no application work here.
    }
    cmd.reset();
    // Build new input, including the program name; do not reuse first.
    std::vector<std::string> second{"prog", "-n", "2"};
    try { cmd.parse(second); }
    catch (const TCLAP::ArgException &) { return 2; }
    std::cout << number.getValue() << '\n';
    return 0;
}

Constraints check values explicitly supplied on the command line. An omitted optional argument has isSet() equal to false, and its default value is intentionally not checked against its constraint. The application decides whether and how to use that default. For example, an optional integer may default to 0 even if its allowed input values are 1 and 2. A required argument must still be supplied: its default does not satisfy the requirement. Read values only after the whole parse succeeds.

For example, one might wish to allow only integers greater than 0. In this case, simply create a class that implements the Constraint<int> interface and checks whether the value parsed is greater than 0 (done in the check() method) and create your Arg with your new Constraint.

TCLAP provides a simple way to constrain the allowed values to a list of values. Simply create a ValuesConstraint object with a vector of values and add that to the Arg.

When the value for the Arg is parsed, it is checked against the list of values specified in the ValuesConstraint. If the value is in the list then it is accepted. If not, then an exception is thrown. Here is a simple example:

		vector<string> allowed;
		allowed.push_back("homer");
		allowed.push_back("marge");
		allowed.push_back("bart");
		allowed.push_back("lisa");
		allowed.push_back("maggie");
		ValuesConstraint<string> allowedVals( allowed );
        
		ValueArg<string> nameArg("n","name","Name to print",true,"homer",&allowedVals);
		cmd.add( nameArg );

When a ValuesConstraint is specified, instead of a type description being specified in the Arg, a type description is created by concatenating the values in the allowed list using operator<< for the specified type. The help/usage for the Arg therefore lists the allowable values. Because of this, you might want to keep the list relatively small, however there is no limit on this.

Each Arg has a constructor that takes a CmdLine object as an argument. Each Arg then adds itself to the CmdLine object. There is no difference in how the Arg is handled between this method and calling the add() method directly. Here is an example:

        // Create the command line.
        CmdLine cmd("this is a message", '=', "0.99" );

        // Note that the following args take the "cmd" object as arguments.
        SwitchArg btest("B","existTestB", "exist Test B", cmd, false );

        ValueArg<string> stest("s", "stringTest", "string test", true, "homer", 
                                               "string", cmd );

        UnlabeledValueArg<string> utest("unTest1","unlabeled test one", 
                                                        "default","string", cmd );
        
        // NO add() calls!

        // Parse the command line.
        cmd.parse(argc,argv);

It is straightforward to change the output generated by TCLAP. Either subclass the StdOutput class and re-implement the methods you choose, or write your own class that implements the CmdLineOutput interface. Once you have done this, then use the CmdLine setOutput method to tell the CmdLine to use your new output class. Here is a simple example:

class MyOutput : public StdOutput
{
	public:
		virtual void failure(CmdLineInterface& c, ArgException& e)
		{ 
			cerr << "My special failure message for: " << endl
				 << e.what() << endl;
			exit(1);
		}

		virtual void usage(CmdLineInterface& c)
		{
			cout << "my usage message:" << endl;
			list<Arg*> args = c.getArgList();
			for (ArgListIterator it = args.begin(); it != args.end(); it++)
				cout << (*it)->longID() 
					 << "  (" << (*it)->getDescription() << ")" << endl;
		}

		virtual void version(CmdLineInterface& c)
		{
			cout << "my version message: 0.1" << endl;
		}
};

int main(int argc, char** argv)
{
		CmdLine cmd("this is a message", ' ', "0.99" );

		// set the output
		MyOutput my;
		cmd.setOutput( &my );

		// proceed normally ...

See test4.cpp in the examples directory for the full example. NOTE: if you supply your own Output object, we will not delete it in the CmdLine destructor. This could lead to a (very small) memory leak if you don't take care of the object yourself. Also note that the failure method is now responsible for exiting the application (assuming that is the desired behavior).

Help and version information is useful for nearly all command line applications and as such we generate flags that provide those options automatically. However, there are situations when these flags are undesirable. For these cases we've added we've added a forth parameter to the CmdLine constructor. Making this boolean parameter false will disable automatic help and version generation.

		CmdLine cmd("this is a message", ' ', "0.99", false );

The automatically registered -- marker ends option recognition. POSIX/GNU conventions treat following tokens as operands, including tokens beginning with a dash; they do not mean that all following input is discarded. TCLAP's ordinary unlabeled arguments consume those tokens in their registered order. The marker itself is not an operand.

For example, with a switch -x and an unlabeled multi argument for files, prog -x before -- -x after sets the switch once and supplies the three operands before, -x and after. The second -x is a file name, not another switch occurrence. Required arguments are still checked after --; the marker does not satisfy missing requirements.

TCLAP implements this through its separate ignoreable policy. Labeled arguments are normally ignoreable, so they stop matching after the marker. Unmatched remaining tokens are not reported as unknown-option errors. Unlabeled arguments are normally not ignoreable and therefore continue consuming input. Passing true for an unlabeled argument's constructor parameter ignoreable makes it stop consuming after the marker as well. This is a TCLAP policy choice, separate from the standard meaning of ending option recognition.

By default, if TCLAP sees an argument that doesn't match a specified Arg, it will produce an exception. This strict handling provides some assurance that all input to a program is controlled. However, there are times when this strict handling of arguments might not be desirable. TCLAP provides two alternatives. The first is to add an UnlabeledMultiArg to the command line. If this is done, all unmatched arguments will get added to this arg. The second option is that that TCLAP can simply ignore any unmatched arguments on the command line. This is accomplished by calling the ignoreUnmatched method with true on the CmdLine object that's been constructed.

    // Define the command line object.
	CmdLine cmd("Command description message", ' ', "0.9");

	// Tell the command line to ignore any unmatched args.
	cmd.ignoreUnmatched(true);

    // Define a value argument and add it to the command line.
	ValueArg<string> nameArg("n","name","Name to print",true,"homer","string");
	cmd.add( nameArg );

    // Parse the args.
    cmd.parse( argc, argv );

Given the program above, if a user were to type:

	% command -n Mike something to ignore

The program would succeed and the name ValueArg would be populated with "Mike" but the strings "something", "to", and "ignore" would simply be ignored by the parser.

NOTE: If both ignoreUnmatched is set to true and an UnlabeledMultiArg is added to the command line, then the UnlabeledMultiArg will "win" and all extra arguments will be added to it rather than be ignored.

Sometimes it's desirable to read integers formatted in decimal, hexadecimal, and octal format. This is now possible by #defining the TCLAP_SETBASE_ZERO directive. Simply define this directive in your code and integer arguments will be parsed in each base.

#define TCLAP_SETBASE_ZERO 1

#include "tclap/CmdLine.h"
#include <iostream>

using namespace TCLAP;
using namespace std;

int main(int argc, char** argv)
{

	try {

	CmdLine cmd("this is a message", ' ', "0.99" );

	ValueArg<int> itest("i", "intTest", "integer test", true, 5, "int");
	cmd.add( itest );

	//
	// Parse the command line.
	//
	cmd.parse(argc,argv);

	//
	// Set variables
	//
	int _intTest = itest.getValue();
	cout << "found int: " << _intTest << endl;

	} catch ( ArgException& e )
	{ cout << "ERROR: " << e.error() << " " << e.argId() << endl; }
}

The reason that this behavior is not the default behavior for TCLAP is that the use of setbase(0) appears to be something of a side effect and is not necessarily how setbase() is meant to be used. So while we're making this functionality available, we're not turning it on by default for fear of bad things happening in different compilers. If you know otherwise, please let us know.

The usual C++ types (int, long, bool, etc.) are supported by TCLAP out of the box. As long as operator>> and operator<< are supported, other types should work fine too, you'll just need to specify the ArgTraits which tells TCLAP how you expect the type to be handled.

For example, assume that you'd like to read one argument on the command line in as a std::pair object. You need to tell TCLAP whether to treat std::pair as a String or Value (default). StringLike means to treat the string on the command line as a string and use it directly (by assignment operator), whereas ValueLike means that a value object should be extracted from the string using operator>>. For std::pair we'll choose ValueLike. Here is an example of how to do this for int,double pair (see test47.cpp):

#include <iostream>
#include <utility>

// We need to tell TCLAP how to parse our pair, we assume it will be
// given as two arguments separated by whitespace.
std::istream &operator>>(std::istream &is, std::pair<int, double> &p) {
  return is >> p.first >> p.second;
}

// Make it easy to print values of our type.
std::ostream &operator<<(std::ostream &os, const std::pair<int, double> &p) {
  return os << p.first << ' ' << p.second;
}

#include "tclap/CmdLine.h"
using namespace TCLAP;

// Our pair can now be used as any other type.
int main(int argc, char **argv) {
  CmdLine cmd("test pair argument");
  ValueArg<std::pair<int, double> > parg("p", "pair", "int,double pair",
                                         true,
                                         std::make_pair(0, 0.0),
                                         "int,double",
                                         cmd);
  cmd.parse(argc, argv);
  std::cout << parg.getValue() << std::endl;
}

Important: When specifying the argument on the command line it needs to be given as a single argument, that is by quoting it. For example, ./test30 -p "1 2.3".

If you do not want to provide operator>>, you can instead use operator= by defining the type as StringLike. A complete example is given in test11.cpp, but the main difference is you need to tell TCLAP to assign to the type using operator=. This is done by defining it as StringLike as shown below:

namespace TCLAP {
template<>
struct ArgTraits<Vect3D> {
    typedef StringLike ValueCategory;
};
}

It is traditional in Posix environments that the "-" and "--" strings are used to signify the beginning of argument flags and long argument names. However, other environments, namely Windows, use different strings. TCLAP allows you to control which strings are used with #define directives. This allows you to use different strings based on your operating environment. Here is an example:

//
// This illustrates how to change the flag and name start strings for 
// Windows, otherwise the defaults are used.
//
// Note that these defines need to happen *before* tclap is included!
//
#ifdef WINDOWS
#define TCLAP_NAMESTARTSTRING "~~"
#define TCLAP_FLAGSTARTSTRING "/"
#endif

#include "tclap/CmdLine.h"

using namespace TCLAP;
using namespace std;

int main(int argc, char** argv)
{
	// Everything else is identical!
	...