rosparam

Access ROS parameter server values

Syntax

list = rosparam("list")

list = rosparam("list",namespace)

pvalOut = rosparam("get",pname)

pvalOut = rosparam("get",namespace)

rosparam("set",pname,pval)

rosparam("delete",pname)

rosparam("delete",namespace)

ptree = rosparam

Description

list = rosparam("list") returns the list of all ROS parameter names from the ROS master.

Simplified form: rosparam list

list = rosparam("list",namespace) returns the list of all parameter names under the specified ROS namespace.

Simplified form: rosparam list namespace

pvalOut = rosparam("get",pname) retrieves the value of the specified parameter.

Simplified form: rosparam get pname

pvalOut = rosparam("get",namespace) retrieves the values of all parameters under the specified namespace as a structure.

Simplified form: rosparam get namespace

rosparam("set",pname,pval) sets a value for a specified parameter name. If the parameter name does not exist, the function adds a new parameter in the parameter tree.

Simplified form: rosparam set pname pval

See Limitations for limitations on pval.

rosparam("delete",pname) deletes a parameter from the parameter tree. If the parameter does not exist, the function displays an error.

Simplified form: rosparam delete pname

rosparam("delete",namespace) deletes all parameters under the given namespace from the parameter tree.

Simplified form: rosparam delete namespace

ptree = rosparam creates a parameter tree object, ptree. After ptree is created, the connection to the parameter server remains persistent until the object is deleted or the ROS master becomes unavailable.

A ROS parameter tree communicates with the ROS parameter server. The ROS parameter server can store strings, integers, doubles, Booleans and cell arrays. The parameters are accessible by every node in the ROS network. Use the parameters to store static data such as configuration parameters. Use the get, set, has, search, and del functions to manipulate and view parameter values.

The following ROS data types are supported as values of parameters. For each ROS data type, the corresponding MATLAB^® data type is also listed.

• 32-bit integer — int32

• Boolean — logical

• double — double

• string — character vector (char)

• list — cell array (cell)

• dictionary — structure (struct)

Examples

Get and Set Parameter Values

Connect to a ROS network to set and get ROS parameter values on the ROS parameter tree. You can get lists of parameters in their given namespaces as well. This example uses the simplified form that mimics the ROS command-line interface.

Connect to a ROS network.

rosinit

Launching ROS Core...
Done in 0.78686 seconds.
Initializing ROS master on http://172.20.219.203:51493.
Initializing global node /matlab_global_node_34580 with NodeURI http://dcc422351glnxa64:37301/ and MasterURI http://localhost:51493.

Set parameter values.

rosparam set /string_param 'param_value'
rosparam set /double_param 1.2

To set a list parameter, use the functional form.

rosparam('set', '/list_param', {int32(5), 124.1, -20, 'some_string'});

Get the list of parameters using the command-line form.

rosparam list

/double_param
/list_param  
/string_param

List parameters in a specific namespace.

rosparam list /double

/double_param

Get the value of a specific parameter.

rosparam get /list_param

{5, 124.1, -20, some_string}

Delete a parameter. List the parameters to verify it was deleted.

rosparam delete /double_param
rosparam list

/list_param  
/string_param

Shut down the ROS network.

rosshutdown

Shutting down global node /matlab_global_node_34580 with NodeURI http://dcc422351glnxa64:37301/ and MasterURI http://localhost:51493.
Shutting down ROS master on http://172.20.219.203:51493.

Create Parameter Tree Object and View Parameters

Connect to the ROS network. ROS parameters should already be available on the ROS master.

rosinit('192.168.17.128')

Initializing global node /matlab_global_node_91663 with NodeURI http://192.168.17.1:52951/

Create a ParameterTree object using rosparam.

ptree = rosparam;

List the available parameters on the ROS master.

ptree.AvailableParameters

ans = 33×1 cell array
    {'/bumper2pointcloud/pointcloud_radius'         }
    {'/camera/imager_rate'                          }
    {'/camera/rgb/image_raw/compressed/format'      }
    {'/camera/rgb/image_raw/compressed/jpeg_quality'}
    {'/camera/rgb/image_raw/compressed/png_level'   }
    {'/cmd_vel_mux/yaml_cfg_file'                   }
    {'/depthimage_to_laserscan/output_frame_id'     }
    {'/depthimage_to_laserscan/range_max'           }
    {'/depthimage_to_laserscan/range_min'           }
    {'/depthimage_to_laserscan/scan_height'         }
    {'/depthimage_to_laserscan/scan_time'           }
    {'/gazebo/auto_disable_bodies'                  }
    {'/gazebo/cfm'                                  }
    {'/gazebo/contact_max_correcting_vel'           }
    {'/gazebo/contact_surface_layer'                }
    {'/gazebo/erp'                                  }
    {'/gazebo/gravity_x'                            }
    {'/gazebo/gravity_y'                            }
    {'/gazebo/gravity_z'                            }
    {'/gazebo/max_contacts'                         }
    {'/gazebo/max_update_rate'                      }
    {'/gazebo/sor_pgs_iters'                        }
    {'/gazebo/sor_pgs_precon_iters'                 }
    {'/gazebo/sor_pgs_rms_error_tol'                }
    {'/gazebo/sor_pgs_w'                            }
    {'/gazebo/time_step'                            }
    {'/robot_description'                           }
    {'/robot_state_publisher/publish_frequency'     }
    {'/rosdistro'                                   }
    {'/roslaunch/uris/host_192_168_17_128__34863'   }
    {'/rosversion'                                  }
    {'/run_id'                                      }
    {'/use_sim_time'                                }

Shut down the ROS network.

rosshutdown

Shutting down global node /matlab_global_node_91663 with NodeURI http://192.168.17.1:52951/

Set A Dictionary Of Parameter Values

Use structures to specify a dictionary of ROS parameters under a specific namespace.

Connect to a ROS network.

rosinit

Launching ROS Core...
Done in 0.66963 seconds.
Initializing ROS master on http://172.30.144.24:59754.
Initializing global node /matlab_global_node_57799 with NodeURI http://dcc796195glnxa64:46883/ and MasterURI http://localhost:59754.

Create a dictionary of parameter values. This dictionary contains the information relevant to an image. Display the structure to verify values.

image = imread('peppers.png');

pval.ImageWidth = size(image,1);
pval.ImageHeight = size(image,2);
pval.ImageTitle = 'peppers.png';
disp(pval)

     ImageWidth: 384
    ImageHeight: 512
     ImageTitle: 'peppers.png'

Set the dictionary of values using the desired namespace.

rosparam('set','ImageParam',pval)

Get the parameters using the namespace. Verify the parameter values.

pval2 = rosparam('get','ImageParam')

pval2 = struct with fields:
    ImageHeight: 512
     ImageTitle: 'peppers.png'
     ImageWidth: 384

Shut down ROS network.

rosshutdown

Shutting down global node /matlab_global_node_57799 with NodeURI http://dcc796195glnxa64:46883/ and MasterURI http://localhost:59754.
Shutting down ROS master on http://172.30.144.24:59754.

Input Arguments

namespace — ROS parameter namespace

string scalar | character vector

ROS parameter namespace, specified as a string scalar or character vector. All parameter names starting with this string are listed when calling rosparam("list",namespace).

pname — ROS parameter name

string scalar | character vector

ROS parameter name, specified as a string scalar or character vector.

pval — ROS parameter value or dictionary of values

int32 | logical | double | string scalar | character vector | cell array | structure

ROS parameter value or dictionary of values, specified as a supported data type.

The following ROS data types are supported as values of parameters. For each ROS data type, the corresponding MATLAB data type is also listed:

• 32-bit integers — int32

• Booleans — logical

• doubles — double

• strings — string scalar, string, or character vector, char

• lists — cell array

• dictionaries — structure

Output Arguments

list — Parameter list

cell array of character vectors

Parameter list, returned as a cell array of character vectors. This is a list of all parameters available on the ROS master.

ptree — Parameter tree

ParameterTree object handle

Parameter tree, returned as a ParameterTree object handle. Use this object to reference parameter information, for example, ptree.AvailableFrames.

pvalOut — ROS parameter value or dictionary of values

int32 | logical | double | character vector | cell array | structure

ROS parameter value, specified as a supported MATLAB data type. When specifying the namespace input argument, pvalOut is returned as a structure of parameter value under the given namespace.

The following ROS data types are supported as values of parameters. For each ROS data type, the corresponding MATLAB data type is also listed.

ROS Data Type	MATLAB Data Type
32-bit integer	int32
Boolean	logical
double	double
string	character vector (char)
list	cell array (cell)
dictionary	structure (struct)

Limitations

• Unsupported Data Types: Base64-encoded binary data and iso8601 data from ROS are not supported.

• Simplified Commands: When using the simplified command rosparam set pname pval, the parameter value is interpreted as:

  • logical — If pval is "true" or "false"

  • int32 — If pval is an integer, for example, 5

  • double — If pval is a fractional number, for example, 1.256

  • character vector — If pval is any other value

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

For code generation, only the following ROS data types are supported as values of parameters,

• 32-bit integer — int32

• Boolean — logical

• double — double

• strings — string scalar, string, or character vector, char

Version History

Introduced in R2019b