bag-cat¶

Introduction¶

Like UNIX cat, the bag-cat program makes a stream of data available on its standard output stream. Unlike UNIX cat, the data is obtained by processing log files.

See bag-record for recording and bag-play for replaying events from log files.

Obtaining bag-cat¶

Binaries of the bag-cat program can be downloaded from the continuous integration server for versions 0.4 and 0.5 of the Robotics Service Bus:

• 0.4 Linux i686
• 0.4 Linux x86_64

• 0.5 Linux i686
• 0.5 Linux x86_64
• 0.5 MacOS x86_64

After the download, the bag-cat file has to be made executable in most cases. This can be done for example by executing

chmod +x bag-cat

in the download directory.

Checking Versions and Displaying Help¶

Version and help information is displayed when the --version and --help[-all] commandline options are specified:

./bag-cat --version
./bag-cat --help
./bag-cat --help-all

The output of --help[-all] includes a list of supported file formats.

Printing the Contents of Log Files¶

When invoked with a log file, bag-cat prints the contents of one or more channels to its standard output stream. This is probably most useful for channels containing textual data, since binary content usually requires a form of decoding.

Example:

./bag-cat isr.tide | head
<sr db_start="80" db_utt="80" />
<sr db_start="45" db_utt="46" />
<?xml version="1.0" encoding="UTF-8" standalone="no" ?><speech_hyp [...]
<?xml version="1.0" encoding="UTF-8" standalone="no" ?><speech_hyp [...]
<?xml version="1.0" encoding="UTF-8" standalone="no" ?><speech_hyp [...]
<?xml version="1.0" encoding="UTF-8" standalone="no" ?><speech_hyp [...]
<?xml version="1.0" encoding="UTF-8" standalone="no" ?><speech_hyp [...]
<speech_hyp xmlns:bxml="http://www.sleepycat.com/2002/dbxml" [...]
<TIMESTAMP>1290275288296</TIMESTAMP>

Selecting Channels for Playback¶

The default behavior of bag-cat is to print the contents of all channels found in the given file. However, when only a subset of the recorded channels should be printed, the --channel (-c) commandline option can be used to select channels. The following example prints the contents all channels matching one of the regular expressions "hyp" and "param".

./bag-cat -c 'hyp' -c 'param' /tmp/nao.tide

Caveats¶

• Individual entries can no longer be distinguished (unless some in-band properties permit this)
• If multiple channels are printed, the channel from which a given part of the output originated is no longer apparent (unless some in-band properties allow determining this)
• Printing channels which contain binary to a terminal content may mess up the terminal and cause all sorts of mayhem