cv::CommandLineParser Class Reference

Designed for command line parsing. More...

#include <utility.hpp>

Public Member Functions
	CommandLineParser (int argc, const char *const argv[], const String &keys)
	Constructor. More...
	CommandLineParser (const CommandLineParser &parser)
	Copy constructor. More...
CommandLineParser &	operator= (const CommandLineParser &parser)
	Assignment operator. More...
	~CommandLineParser ()
	Destructor. More...
String	getPathToApplication () const
	Returns application path. More...
template<typename T >
T	get (const String &name, bool space_delete=true) const
	Access arguments by name. More...
template<typename T >
T	get (int index, bool space_delete=true) const
	Access positional arguments by index. More...
bool	has (const String &name) const
	Check if field was provided in the command line. More...
bool	check () const
	Check for parsing errors. More...
void	about (const String &message)
	Set the about message. More...
void	printMessage () const
	Print help message. More...
void	printErrors () const
	Print list of errors occurred. More...

Protected Member Functions
void	getByName (const String &name, bool space_delete, Param type, void *dst) const
void	getByIndex (int index, bool space_delete, Param type, void *dst) const

Protected Attributes
Impl *	impl

Detailed Description

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:

1. argument names is a list of option synonyms separated by standard space characters ' ' (to mark argument as positional, prefix it with the @ symbol)
2. default value will be used if the argument was not provided (can be empty)
3. 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. Note that whitespace characters other than standard spaces are considered part of the string. Additionally, leading and trailing standard spaces around the help messages are ignored.

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]

Constructor & Destructor Documentation

CommandLineParser() [1/2]

cv::CommandLineParser::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() [2/2]

cv::CommandLineParser::CommandLineParser

(

const CommandLineParser &

parser

)

Copy constructor.

~CommandLineParser()

cv::CommandLineParser::~CommandLineParser

(

)

Destructor.

Member Function Documentation

about()

void cv::CommandLineParser::about

(

const String &

message

)

Set the about message.

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

check()

bool cv::CommandLineParser::check

(

)

const

Check for parsing errors.

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

get() [1/2]

template<typename T >

T cv::CommandLineParser::get ( const String &  name, bool  space_delete = true  ) const

inline

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");

Parameters

name	name of the argument
space_delete	remove spaces from the left and right of the string

Template Parameters

T	the argument will be converted to this type if possible

Note

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

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

get() [2/2]

template<typename T >

T cv::CommandLineParser::get ( int  index, bool  space_delete = true  ) const

inline

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

Template Parameters

T	the argument will be converted to this type if possible

getByIndex()

void cv::CommandLineParser::getByIndex ( int  index, bool  space_delete, Param  type, void *  dst  ) const

protected

getByName()

void cv::CommandLineParser::getByName ( const String &  name, bool  space_delete, Param  type, void *  dst  ) const

protected

getPathToApplication()

String cv::CommandLineParser::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 a command:

$ ./bin/my-executable

this method will return ./bin.

has()

bool cv::CommandLineParser::has

(

const String &

name

)

const

Check if field was provided in the command line.

Parameters

name	argument name to check

operator=()

CommandLineParser& cv::CommandLineParser::operator=

(

const CommandLineParser &

parser

)

Assignment operator.

printErrors()

void cv::CommandLineParser::printErrors

(

)

const

Print list of errors occurred.

See also

check

printMessage()

void cv::CommandLineParser::printMessage

(

)

const

Print help message.

This method will print standard help message containing the about message and arguments description.

See also

about

Member Data Documentation

impl

Impl* cv::CommandLineParser::impl

protected

---

The documentation for this class was generated from the following file:

• build/release/_deps/opencv-src/include/opencv4/opencv2/core/utility.hpp