Wondering what this line meant, especially the 2>&1 and ${RUN_DIR} parts:
${RUN_DIR}/<filename> 2>&1
Where <filename> is the location and name of a file.
${RUN_DIR}
evaluates whatever the variable RUN_DIR is, and translates it
like: RUN_DIR=/my/path
2>&1 dups (duplicates) the output of stderr (2) into stdout (1).
In other words all of the program output is available on just one output file descriptor - the stdout (usually a terminal) device.
And <filename> is probably just that - a file name with no path.