Launch file syntax doubt

What do “cat” and “-d” mean in the following code?


Is a UNIX shell command to print the contents of a file. For example:

cat test.txt

This will print the contents of the test.txt file.

As for the


Is a command for rviz that indicates RVIZ to load from a certain previously saved .rviz file. This allows it to open with laser elements, camera or certain tfs selected. Is the default way of laoding rviz with a file.