OpenCV  3.4.0-rc
Open Source Computer Vision
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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 ()
 Destructor. More...
 
void about (const String &message)
 Set the about message. More...
 
bool check () const
 Check for parsing errors. 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...
 
String getPathToApplication () const
 Returns application path. More...
 
bool has (const String &name) const
 Check if field was provided in the command line. More...
 
CommandLineParseroperator= (const CommandLineParser &parser)
 Assignment operator. More...
 
void printErrors () const
 Print list of errors occurred. More...
 
void printMessage () const
 Print help message. More...
 

Protected Member Functions

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
 

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 space-separated list of option synonyms (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.

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]
Examples:
camshiftdemo.cpp, contours2.cpp, convexhull.cpp, cout_mat.cpp, demhist.cpp, distrans.cpp, edge.cpp, facedetect.cpp, ffilldemo.cpp, filestorage.cpp, fitellipse.cpp, fld_lines.cpp, grabcut.cpp, hog.cpp, image_alignment.cpp, laplace.cpp, lkdemo.cpp, lsd_lines.cpp, morphology2.cpp, pca.cpp, peopledetect.cpp, polar_transforms.cpp, segment_objects.cpp, shape_example.cpp, Sobel_Demo.cpp, train_HOG.cpp, warpPerspective_demo.cpp, and watershed.cpp.

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
argcnumber of command line arguments (from main())
argvarray of command line arguments (from main())
keysstring 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 true if error occurred while accessing the parameters (bad conversion, missing arguments, etc.). Call printErrors to print error messages list.

Examples:
facedetect.cpp, laplace.cpp, and shape_example.cpp.

§ 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
namename of the argument
space_deleteremove spaces from the left and right of the string
Template Parameters
Tthe argument will be converted to this type if possible
Note
You can access positional arguments by their @-prefixed name:
parser.get<String>("@image");
Examples:
camshiftdemo.cpp, demhist.cpp, distrans.cpp, edge.cpp, facedetect.cpp, ffilldemo.cpp, filestorage.cpp, fitellipse.cpp, fld_lines.cpp, grabcut.cpp, hog.cpp, laplace.cpp, lkdemo.cpp, lsd_lines.cpp, morphology2.cpp, pca.cpp, peopledetect.cpp, polar_transforms.cpp, segment_objects.cpp, shape_example.cpp, Sobel_Demo.cpp, warpPerspective_demo.cpp, and watershed.cpp.

§ 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
indexindex of the argument
space_deleteremove spaces from the left and right of the string
Template Parameters
Tthe argument will be converted to this type if possible

§ getByIndex()

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

§ getByName()

void cv::CommandLineParser::getByName ( const String name,
bool  space_delete,
int  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

§ operator=()

CommandLineParser& cv::CommandLineParser::operator= ( const CommandLineParser parser)

Assignment operator.

§ printErrors()

void cv::CommandLineParser::printErrors ( ) const

Print list of errors occurred.

See also
check
Examples:
facedetect.cpp, laplace.cpp, and shape_example.cpp.

§ 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
Examples:
camshiftdemo.cpp, ffilldemo.cpp, fld_lines.cpp, hog.cpp, lsd_lines.cpp, pca.cpp, peopledetect.cpp, and Sobel_Demo.cpp.

Member Data Documentation

§ impl

Impl* cv::CommandLineParser::impl
protected

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