What parameter parser libraries are there for C++?

Question

I'd like to pass parameters to my C++ program in the following manner:

./myprog --setting=value

Are there any libraries which will help me to do this easily?

See also Argument-parsing helpers for C and Unix

Answer 1

Boost.Program_options

Answer 2

GNU GetOpt.

A simple example using GetOpt:

// C/C++ Libraries:
#include <string>
#include <iostream>
#include <unistd.h>

// Namespaces:
using namespace std;

int main(int argc, char** argv) {
    int opt;
    bool flagA = false;
    bool flagB = false;

    // Shut GetOpt error messages down (return '?'): 
    opterr = 0;

    // Retrieve the options:
    while ( (opt = getopt(argc, argv, "ab")) != -1 ) {  // for each option...
        switch ( opt ) {
            case 'a':
                    flagA = true;
                break;
            case 'b':
                    flagB = true;
                break;
            case '?':  // unknown option...
                    cerr << "Unknown option: '" << char(optopt) << "'!" << endl;
                break;
        }
    }

    // Debug:
    cout << "flagA = " << flagA << endl;
    cout << "flagB = " << flagB << endl;

    return 0;
}

You can also use optarg if you have options that accept arguments.

Answer 3

There are these tools in the GNU C Library, which includes GetOpt.

If you are using Qt and like the GetOpt interface, froglogic has published a nice interface here.

Answer 4

Tooting my own horn if I may, I'd also like to suggest taking a look at an option parsing library that I've written: dropt.

• It's a C library (with a C++ wrapper if desired).
• It's lightweight.
• It's extensible (custom argument types can be easily added and have equal footing with built-in argument types).
• It should be very portable (it's written in standard C) with no dependencies (other than the C standard library).
• It has a very unrestrictive license (zlib/libpng).

One feature that it offers that many others don't is the ability to override earlier options. For example, if you have a shell alias:

alias bar="foo --flag1 --flag2 --flag3"

and you want to use bar but with--flag1 disabled, it allows you to do:

bar --flag1=0

Answer 5

Try CLPP library. It's simple and flexible library for command line parameters parsing. Header-only and cross-platform. Uses ISO C++ and Boost C++ libraries only. IMHO it is easier than Boost.Program_options.

Library: http://sourceforge.net/projects/clp-parser/

26 October 2010 - new release 2.0rc. Many bugs fixed, full refactoring of the source code, documentation, examples and comments have been corrected.

Answer 6

I think that GNU GetOpt is not too immediate to use.

Qt and Boost could be a solution, but you need to download and compile a lot of code.

So I implemented a parser by myself that produces a std::map<std::string, std::string> of parameters.

For example, calling:

 ./myProgram -v -p 1234

map will be:

 ["-v"][""]
 ["-p"]["1234"]

Usage is:

int main(int argc, char *argv[]) {
    MainOptions mo(argc, argv);
    MainOptions::Option* opt = mo.getParamFromKey("-p");
    const string type = opt ? (*opt).second : "";
    cout << type << endl; /* Prints 1234 */
    /* Your check code */
}

MainOptions.h

#ifndef MAINOPTIONS_H_
#define MAINOPTIONS_H_

#include <map>
#include <string>

class MainOptions {
public:
    typedef std::pair<std::string, std::string> Option;
    MainOptions(int argc, char *argv[]);
    virtual ~MainOptions();
    std::string getAppName() const;
    bool hasKey(const std::string&) const;
    Option* getParamFromKey(const std::string&) const;
    void printOptions() const;
private:
    typedef std::map<std::string, std::string> Options;
    void parse();
    const char* const *begin() const;
    const char* const *end() const;
    const char* const *last() const;
    Options options_;
    int argc_;
    char** argv_;
    std::string appName_;
};

MainOptions.cpp

#include "MainOptions.h"

#include <iostream>

using namespace std;

MainOptions::MainOptions(int argc, char* argv[]) :
        argc_(argc),
        argv_(argv) {
    appName_ = argv_[0];
    this->parse();
}

MainOptions::~MainOptions() {
}

std::string MainOptions::getAppName() const {
    return appName_;
}

void MainOptions::parse() {
    typedef pair<string, string> Option;
    Option* option = new pair<string, string>();
    for (const char* const * i = this->begin() + 1; i != this->end(); i++) {
        const string p = *i;
        if (option->first == "" && p[0] == '-') {
            option->first = p;
            if (i == this->last()) {
                options_.insert(Option(option->first, option->second));
            }
            continue;
        } else if (option->first != "" && p[0] == '-') {
            option->second = "null"; /* or leave empty? */
            options_.insert(Option(option->first, option->second));
            option->first = p;
            option->second = "";
            if (i == this->last()) {
                options_.insert(Option(option->first, option->second));
            }
            continue;
        } else if (option->first != "") {
            option->second = p;
            options_.insert(Option(option->first, option->second));
            option->first = "";
            option->second = "";
            continue;
        }
    }
}

void MainOptions::printOptions() const {
    std::map<std::string, std::string>::const_iterator m = options_.begin();
    int i = 0;
    if (options_.empty()) {
        cout << "No parameters\n";
    }
    for (; m != options_.end(); m++, ++i) {
        cout << "Parameter [" << i << "] [" << (*m).first << " " << (*m).second
                << "]\n";
    }
}

const char* const *MainOptions::begin() const {
    return argv_;
}

const char* const *MainOptions::end() const {
    return argv_ + argc_;
}

const char* const *MainOptions::last() const {
    return argv_ + argc_ - 1;
}

bool MainOptions::hasKey(const std::string& key) const {
    return options_.find(key) != options_.end();
}

MainOptions::Option* MainOptions::getParamFromKey(
        const std::string& key) const {
    const Options::const_iterator i = options_.find(key);
    MainOptions::Option* o = 0;
    if (i != options_.end()) {
        o = new MainOptions::Option((*i).first, (*i).second);
    }
    return o;
}