The files in gr-tagutils are useful for experimenting with Stream Tags in GNU Radio (ver 3.7 or later).

Naviagate to your desired install directory. This should be outside of the main GNU Radio source code directory. From the terminal:

git clone https://github.com/adamgann/gr-tagutils.git
cd gr-tagutils
mkdir build
cd build
cmake ..
make
sudo make install
sudo ldconfig

Searches for a stream tag matching the key parameter and gets its value. If the value is above the threshold, copies the input to the 'above' port If the value is above the threshold, copies the input to the 'below' port User can select to which port the input is copied to when value equals threshold

Searches the input stream for a tag with a key matching the Tag Key field. Outputs zeros when input does not contain a tag. Outputs ones when input does contain a tag. Can be followed by a file sink. Useful for offline processing when one wants to know where tags occur relative to data.

Passes data through adding a tag at a certain offset with a value and key set in the block parameters. Useful for debugging a block that relies on its input having a tag at a certain sample.

Similar to tag to byte. Creates a vector of zeros with non-zero elements when the input contains a tag. Instead of simply a value of one, the output when there is a tag will be equal to the tag's value. Useful for offline processing.