ROS has its own topic-based mechanism, called rosout for recording log messages from nodes. These log messages are human-readable string messages that convey the status of a node.
Viewing these statements in real-time is best done through the rqt_console GUI application (former rxconsole).
Log Statements
roscpp uses the rosconsole package to provide its client-side API. That API takes the form of a number of ROS_ macros:
rosconsole provides eight different types of logging statements, at 5 different verbosity levels, with both printf- and stream-style formatting. Their name syntax is: ROS_<verbosity level>[_STREAM][_<other>]. For example, there are 5 versions of base printf- macro: ROS_DEBUG, ROS_INFO, ROS_WARN, ROS_ERROR and ROS_FATAL.
Note: the sections below only show examples for the DEBUG verbosity. Macros for the other verbosity levels follow the same pattern, just replace DEBUG with the appropriate level (ie: replace DEBUG with INFO for the INFO-level, etc).
Base
ROS_DEBUG(...)
ROS_DEBUG_STREAM(args)
The base versions output to a logger named "ros.<your_package_name>".
Named
ROS_DEBUG_NAMED(name, ...)
ROS_DEBUG_STREAM_NAMED(name, args)
This will output to a logger named "ros.<your_package_name>.test_only". You can see the loggers using rqt_logger_level. More information about this is available in the configuration file section.
Do not use a variable with changing value as the name
Each named logger is stored in a static variable which is initialized on the use of the macro. Either use a string or a variable which string value is not going to change for future invocations since they won't be affecting the logger anymore.
Conditional
ROS_DEBUG_COND(cond, ...)
ROS_DEBUG_STREAM_COND(cond, args)
Conditional Named
ROS_DEBUG_COND_NAMED(cond, name, ...)
ROS_DEBUG_STREAM_COND_NAMED(cond, name, args)
Once [1.1+]
ROS_DEBUG_ONCE(...)
ROS_DEBUG_STREAM_ONCE(args)
ROS_DEBUG_ONCE_NAMED(name, ...)
ROS_DEBUG_STREAM_ONCE_NAMED(name, args)
Throttle [1.1+]
ROS_DEBUG_THROTTLE(period, ...)
ROS_DEBUG_STREAM_THROTTLE(period, args)
ROS_DEBUG_THROTTLE_NAMED(period, name, ...)
ROS_DEBUG_STREAM_THROTTLE_NAMED(period, name, args)
Delayed throttle (added in Indigo as of rosconsole version 1.11.11)
ROS_DEBUG_DELAYED_THROTTLE(period, ...)
ROS_DEBUG_STREAM_DELAYED_THROTTLE(period, args)
ROS_DEBUG_DELAYED_THROTTLE_NAMED(period, name, ...)
ROS_DEBUG_STREAM_DELAYED_THROTTLE_NAMED(period, name, args)
1 while (!ros::service::waitForService("add_two_ints", ros::Duration(0.1)) && ros::ok()) 2 { 3 // This message will print every 10 seconds. 4 // The macro will have no effect the first 10 seconds. 5 // In other words, if the service is not available, the message will be 6 // printed at times 10, 20, 30, ... 7 ROS_DEBUG_DELAYED_THROTTLE(10, "Waiting for service 'add_two_ints'"); 8 }
Filter [1.1+]
ROS_DEBUG_FILTER(filter, ...)
ROS_DEBUG_STREAM_FILTER(filter, args)
ROS_DEBUG_FILTER_NAMED(filter, name, ...)
ROS_DEBUG_STREAM_FILTER_NAMED(filter, name, args)
Filtered output allows you to specify a user-defined filter that extends the ros::console::FilterBase class. Your filter must be a pointer type.
The five different verbosity levels are, in order:
- DEBUG
- INFO
- WARN
- ERROR
- FATAL
rosconsole lets you disable or enable verbosity levels for specific packages and named loggers. For more information on the specifics of rosconsole, please see the rosconsole page.
The default verbosity level is INFO, so DEBUG statements will not be seen by default.
Output
There are four potential places a log message may end up, depending on the verbosity level:
stdout
DEBUG and INFO messages arrive on stdout if they are enabled. Note that this may not be sent to the screen depending on the value of the roslaunch/XML/node output parameter.
stderr
WARN, ERROR and FATAL messages arrive on stderr if they are enabled.
Node log file
Everything enabled goes into the log file. Your node's log file will be in ~/.ros/log unless you override it with the ROS_HOME or ROS_LOG_DIR environment variables. If you are using roslaunch, you can use the roslaunch-logs command to tell you the location of the log directory.
/rosout topic
Everything enabled is sent to the /rosout topic. Note that until the node is fully started, messages will not be sent, so you may not see initial messages.
Here is a table summarizing the above:
|
Debug |
Info |
Warn |
Error |
Fatal |
stdout |
X |
X |
|
|
|
stderr |
|
|
X |
X |
X |
log file |
X |
X |
X |
X |
X |
/rosout |
X |
X |
X |
X |
X |
Also note that this table is different for rospy.
Setting Verbosity Levels
There are three ways of setting verbosity levels on a roscpp node. The first is through a configuration file which sets the verbosity level for every node in the system, the second is at runtime through the rqt_logger_level (former rxloggerlevel) or rqt_console (former rxconsole) tools, and the third is programmatically through the rosconsole API:
#include <ros/console.h> if( ros::console::set_logger_level(ROSCONSOLE_DEFAULT_NAME, ros::console::levels::Debug) ) { ros::console::notifyLoggerLevelsChanged(); }
See the rosconsole documentation for details.
Disable logging to /rosout
Broadcasting rosconsole output to the /rosout topic can be disabled with an Initialization Option or since roscpp 1.14.4 with the ROSCPP_NO_ROSOUT environment variable.