roscpp/Overview/Logging

Contents

Log Statements
Output
Setting Verbosity Levels

ROS has it's 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 rxconsole GUI application.

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 four different types of logging statements, at 5 different verbosity levels, with both printf- and stream-style formatting.

Base
- ROS_DEBUG(...)
- ROS_DEBUG_STREAM(args)
The base versions simply print an output message, ie:
- ```
   1 #include <ros/console.h>
   2 ROS_DEBUG("Hello %s", "World");
   3 ROS_DEBUG_STREAM("Hello " << "World");
```
The base versions output to a logger named "ros.<your_package_name>".
Named
- ROS_DEBUG_NAMED(name, ...)
- ROS_DEBUG_STREAM_NAMED(name, args)
The named versions output to a logger that is a child of the default one. This allows you to configure different logging statements to be enabled/disabled based on their name. For example:
- ```
   1 #include <ros/console.h>
   2 ROS_DEBUG_NAMED("test_only", "Hello %s", "World");
   3 ROS_DEBUG_STREAM_NAMED("test_only", "Hello " << "World");
```
This will output to a logger named "ros.<your_package_name>.test_only". More information about this is available in the configuration file section.
Conditional
- ROS_DEBUG_COND(cond, ...)
- ROS_DEBUG_STREAM_COND(cond, args)
The conditional versions will only output if the condition provided is true. The condition itself will only be evaluated if the logging statement itself is enabled.
- ```
   1 #include <ros/console.h>
   2 ROS_DEBUG_COND(x < 0, "Uh oh, x = %d, this is bad", x);
   3 ROS_DEBUG_STREAM_COND(x < 0, "Uh oh, x = " << x << ", this is bad");
```
Conditional Named
- ROS_DEBUG_COND_NAMED(cond, name, ...)
- ROS_DEBUG_STREAM_COND_NAMED(cond, name, args)
The named conditional versions are just combinations of the above:
- ```
   1 #include <ros/console.h>
   2 ROS_DEBUG_COND_NAMED(x < 0, "test_only", "Uh oh, x = %d, this is bad", x);
   3 ROS_DEBUG_STREAM_COND_NAMED(x < 0, "test_only", "Uh oh, x = " << x << ", this is bad");
```
Once [1.1+]
- ROS_DEBUG_ONCE(...)
- ROS_DEBUG_STREAM_ONCE(args)
- ROS_DEBUG_ONCE_NAMED(name, ...)
- ROS_DEBUG_STREAM_ONCE_NAMED(name, args)
These macros will only every print out a warning the first time the macro is hit and enabled.
- ```
   1 #include <ros/console.h>
   2 for (int i = 0; i < 10; ++i)
   3 {
   4   ROS_DEBUG_ONCE("This message will only print once");
   5 }
```
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)
Throttled output will print a message at most once per "period".
- ```
   1 while (true)
   2 {
   3   ROS_DEBUG_THROTTLE(60, "This message will print every 60 seconds");
   4 }
```
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 two 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 rxloggerlevel or rxconsole tools.

See the rosconsole documentation for details.

Wiki

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User

Log Statements

Output

Setting Verbosity Levels