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How to roslaunch a rostopic echo to text file.

asked 2015-01-14 00:32:45 -0600

Orso gravatar image

I would like to do something like this from a launch file:

rostopic echo -p /mytopic > outputfile.txt

I wrote this in the launch file:

<node name="pioneer3at" pkg="rostopic" type="rostopic" output="screen" args="echo -p /tf_P3AT > outputfile.txt">

</node>

However, it doesn't work and I received an error like this:

Usage: rostopic echo [options] /topic

rostopic: error: you may only specify one input topic
[pioneer3at-1] process has died [pid 3482, exit code 2, cmd /opt/ros/indigo/lib/rostopic/rostopic echo -p /tf_P3AT > outputfile.txt __name:=pioneer3at __log:=/home/danieladmin/.ros/log/873003e4c-9bb4-11e4-8a96-08002709c13/pioneer3at-1*.log].

log file: /home/user/.ros/log/edae921e-f970-11e2-be82-14feb5b7467c/output_topic1-8*.log

Similar to as listed in this question:

http://answers.ros.org/question/70009...

If I delete the part that saves to file, specifically:

> outputfile.txt

I am able to print the args to screen. Does xml have another command that I may use for > to save to file? Else do I need some other work around?

Also, I prefer not to use a bag file in this instance for my workflow.

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Why the option parameter -p ? I cannot find it in the echo man page

Andromeda gravatar imageAndromeda ( 2015-01-14 01:14:32 -0600 )edit

-p Displays messages in a matlab/octave-friendly plotting format. Cannot be used with -c. Check here: link text

Orso gravatar imageOrso ( 2015-01-14 01:22:35 -0600 )edit

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answered 2015-01-14 01:46:58 -0600

Wolf gravatar image

It is not possible to do it like this because > outputfile.txt is a bash / shell specific operation. Unlike -p /tf_P3AT which are passed to the executable as argv to its main( int argc, char** argv ) function the part > outputfile.txt is handled by the shell itself. Therefore if used in a launch file roslaunch would have to handle it, which it is not able to.

So you need another solution. Maybe you can ad the node without > outputfile.txt and set output attribute to log. http://wiki.ros.org/roslaunch/XML/nod... Then you should find a log somewhere in $ROS_HOME/log, which defaults to $HOME/.ros/log. However, I am not sure how/if you can specifiy the log name. Maybe run rosclean purge to remove previous log files so it'll be easier to find the log file of you node....

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Another possible solution would be to write a bash script that calls rostopic with the redirection >. Then make this script executable and ensure it has a hash-bang. Then you should be able to run this script using a standard <node> tag.

jarvisschultz gravatar imagejarvisschultz ( 2015-01-14 07:32:49 -0600 )edit
  • I will try your solution @jarvisschultz, then re-post my solution.
  • Writing to a log file works, but I could not specify another log name, unless I edit the default of $ROS_HOME/log. Also, the log file did not store my header or timestamp. Do I need to call this data in my launch file??
Orso gravatar imageOrso ( 2015-01-14 08:39:44 -0600 )edit

Here is my bash script:

#! /usr/bin/env sh
"true" ; exec /usr/bin/env sbcl --script "$0" "$@"
rostopic echo -p /tf_P3AT > test.txt

I receive: Unhandled UNBOUND-VARIABLE in thread #<sb-thread:thread "main="" thread"="" running="" {1002a8c073}&gt;:="" the="" variable="" rostopic="" is="" unbound.="" and="" a="" backtrace.<="" p="">

Orso gravatar imageOrso ( 2015-01-15 12:08:06 -0600 )edit
1

That seems like an error in the way your script is running sbcl (I'm not sure what is wrong). AFAIK, there is nothing wrong with my suggestion. I just tested it, and it worked fine. My script only contained the rostopic part, and it had its own node tag in my launch file.

jarvisschultz gravatar imagejarvisschultz ( 2015-01-15 12:31:30 -0600 )edit

So I changed the bash script as you suggested to:

#! /usr/bin/env sh
rostopic echo -p /tf_P3AT > test.txt

It saves to /.ros/log. Do you know of a way to save to a specified folder? Also, I lose my header and timestamp in the log file. Thanks.

Orso gravatar imageOrso ( 2015-01-15 12:48:02 -0600 )edit

Changed my bash script to:

rostopic echo -p /tf_P3AT > /home/danieladmin/test.txt

This saves to home with timestamp and header. Launched with the following launch file:

<node pkg="pioneer3at" name="foo" type="SensorLaunchBash" />

Thanks @jarvisschultz. Why did I not need a hash-bang?

Orso gravatar imageOrso ( 2015-01-15 13:13:18 -0600 )edit

You could (and probably should) have the hash-bang. If it's not there, many shells will guess that the file is a script and run it with the same shell. For your situation, this happened to work, but likely wouldn't always work. http://stackoverflow.com/a/12296783/1...

jarvisschultz gravatar imagejarvisschultz ( 2015-01-15 13:36:36 -0600 )edit

@Orso this is great! In order to change the name of the test.txt file, I created another python script that is run once my launch file ends. My script looks like this. Call it with:

roslaunch package file.launch && rename_log.py
flurin4 gravatar imageflurin4 ( 2018-01-23 02:53:02 -0600 )edit

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Asked: 2015-01-14 00:32:45 -0600

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Last updated: Jan 14 '15