class cv::CommandLineParser

Overview

Designed for command line parsing. More…

#include <utility.hpp>

class CommandLineParser
{
public:
    // construction

    CommandLineParser(
        int argc,
        const char*const argv [],
        const String& keys
        );

    CommandLineParser(const CommandLineParser& parser);

    // methods

    void
    about(const String& message);

    bool
    check() const;

    template <typename T>
    T
    get(
        const String& name,
        bool space_delete = true
        ) const;

    template <typename T>
    T
    get(
        int index,
        bool space_delete = true
        ) const;

    String
    getPathToApplication() const;

    bool
    has(const String& name) const;

    CommandLineParser&
    operator=(const CommandLineParser& parser);

    void
    printErrors() const;

    void
    printMessage() const;

protected:
    // fields

    Impl* impl;

    // methods

    void
    getByIndex(
        int index,
        bool space_delete,
        int type,
        void* dst
        ) const;

    void
    getByName(
        const String& name,
        bool space_delete,
        int type,
        void* dst
        ) const;
};

Detailed Documentation

Designed for command line parsing.

The sample below demonstrates how to use CommandLineParser :

CommandLineParser parser(argc, argv, keys);
parser.about("Application name v1.0.0");

if (parser.has("help"))
{
    parser.printMessage();
    return 0;
}

int N = parser.get<int>("N");
double fps = parser.get<double>("fps");
String path = parser.get<String>("path");

use_time_stamp = parser.has("timestamp");

String img1 = parser.get<String>(0);
String img2 = parser.get<String>(1);

int repeat = parser.get<int>(2);

if (!parser.check())
{
    parser.printErrors();
    return 0;
}

Keys syntax

The keys parameter is a string containing several blocks, each one is enclosed in curly braces and describes one argument. Each argument contains three parts separated by the | symbol:

argument names is a space-separated list of option synonyms (to mark argument as positional, prefix it with the @ symbol)
default value will be used if the argument was not provided (can be empty)
help message (can be empty)

For example:

    const String keys =
        "{help h usage ? |      | print this message   }"
        "{@image1        |      | image1 for compare   }"
        "{@image2        |<none>| image2 for compare   }"
        "{@repeat        |1     | number               }"
        "{path           |.     | path to file         }"
        "{fps            | -1.0 | fps for output video }"
        "{N count        |100   | count of objects     }"
        "{ts timestamp   |      | use time stamp       }"
        ;
}

Note that there are no default values for help and timestamp so we can check their presence using the has() method. Arguments with default values are considered to be always present. Use the get() method in these cases to check their actual value instead.

String keys like get<String>("@image1") return the empty string "" by default - even with an empty default value. Use the special <none> default value to enforce that the returned string must not be empty. (like in get<String>("@image2"))

Usage

For the described keys:

# Good call (3 positional parameters: image1, image2 and repeat; N is 200, ts is true)
$ ./app -N=200 1.png 2.jpg 19 -ts

# Bad call
$ ./app -fps=aaa
ERRORS:
Parameter 'fps': can not convert: [aaa] to [double]

Construction

CommandLineParser(
    int argc,
    const char*const argv [],
    const String& keys
    )

Constructor.

Initializes command line parser object

Parameters:

argc	number of command line arguments (from main())
argv	array of command line arguments (from main())
keys	string describing acceptable command line parameters (see class description for syntax)

CommandLineParser(const CommandLineParser& parser)

Copy constructor.

Methods

void
about(const String& message)

Set the about message.

The about message will be shown when printMessage is called, right before arguments table.

bool
check() const

Check for parsing errors.

Returns true if error occurred while accessing the parameters (bad conversion, missing arguments, etc.). Call printErrors to print error messages list.

template <typename T>
T
get(
    const String& name,
    bool space_delete = true
    ) const

Access arguments by name.

Returns argument converted to selected type. If the argument is not known or can not be converted to selected type, the error flag is set (can be checked with check).

For example, define:

String keys = "{N count||}";

Call:

$ ./my-app -N=20
# or
$ ./my-app --count=20

Access:

int N = parser.get<int>("N");

You can access positional arguments by their @ -prefixed name:

parser.get<String>("@image");

Parameters:

name	name of the argument
space_delete	remove spaces from the left and right of the string
T	the argument will be converted to this type if possible

template <typename T>
T
get(
    int index,
    bool space_delete = true
    ) const

Access positional arguments by index.

Returns argument converted to selected type. Indexes are counted from zero.

For example, define:

String keys = "{@arg1||}{@arg2||}"

Call:

./my-app abc qwe

Access arguments:

String val_1 = parser.get<String>(0); // returns "abc", arg1
String val_2 = parser.get<String>(1); // returns "qwe", arg2

Parameters:

index	index of the argument
space_delete	remove spaces from the left and right of the string
T	the argument will be converted to this type if possible

String
getPathToApplication() const

Returns application path.

This method returns the path to the executable from the command line (argv[0]).

For example, if the application has been started with such command:

$ ./bin/my-executable

this method will return ./bin.

bool
has(const String& name) const

Check if field was provided in the command line.

Parameters:

name	argument name to check

CommandLineParser&
operator=(const CommandLineParser& parser)

Assignment operator.

void
printErrors() const

Print list of errors occured.