On Thu, Feb 26, 2015 at 1:10 AM, jannik laval <jannik.laval@gmail.com> wrote:

Hi Dave,

2015-02-25 17:05 GMT+01:00 David T. Lewis <lewis@mail.msen.com>:

Hi Jannik,

One other thing I just thought of: Check and see if your rostopic program
is actually writing to standard output, as opposed to writing directly to
/dev/tty. From a terminal window, I think you could do this:

$ rostopic > out.txt

Yes, it writes on the file after a ctrl-c.

Is that a hint?�� So if in one terminal you run $ rostopic > out.txt��

then without hitting ctrl-c, in another terminal view the contents of out.txt, is it empty?��

Do you get different behaviour with this between each of these mode [1]?...

• Latching mode

  • rostopic��will publish a message to��/topic_name��and keep it��latched��-- any new subscribers that come online after you start��rostopic��will hear this message. You can stop this at any time by pressing��ctrl-C.

  Once mode

  • If you don't want to have to stop rostopic with��ctrl-C, you can publish in��once mode.��rostopic��will keep the message latched for 3 seconds, then quit.

  Rate mode.

  • In rate mode,��rostopic��will publish your message at a specific rate. For example,��-r��10��will publish at 10hz. For file and piped input, this defaults to 10hz.

Options:

• -l,��--latch��New in Diamondback

  • Enable latch mode. Latching mode is the��default��when using command-line arguments.

  -r��RATE

  • Enable��rate mode. Rate mode is the��default��(10hz) when using piped or file input.

  -1,��--once

• Enable��once mode.

cheers -ben

[1]��http://wiki.ros.org/rostopic#rostopic_pub

[2]��http://answers.ros.org/question/59070/disable-latching-for-rostopic-in-piping-mode/