= NAME =
set_overlay_vars

= SYNOPSIS =
set_overlay_vars

= DESCRIPTION =
This function implements the overlay system in Fuego.

Specifically, it does some sanity checking to make sure that the requested
overlay files exist (that is, the board file, distribution file, and the testplan file).  the it calls [[ovgen.py]] to generate a shell script based
on these files.

The shell script has the name $NODE_NAME-prolog.sh, and it is placed
in the directory /fuego-rw/work.  This "prolog" shell script is the product
of looking up the testplan, and generating a set of variables based on
the test specs that are listed in it.

The list of variables is from all the different tests and specs related
to that test plan, which may have references to board, distribution and
system variables.

Once this xxx-prolog.sh file is created, it is sourced into the current
shell environment.  It can also be sourced independently of the currently
running script, to get access to all of the same test variables for a 
particular plan, board, and set of tests.

See [[Test Specs and Plans]] for details about how Fuego uses test plans and specs to create test variants.

= EXAMPLES =
Here are some sample invocations:
{{{#!YellowBox
set_overlay_vars
}}}

= ENVIRONMENT and ARGUMENTS =
This function uses the following environment arguments:
 * $NODE_NAME - the name of the board
 * $DISTRIB - the name of the distribution to use
 * $BATCH_TESTPLAN - name of the testplan (with a list of tests and their specs)
 * $TESTPLAN - name of the testplan (with a list of tests and their specs)

Only one of $BATCH_TESTPLAN and $TESTPLAN needs to be defined.

If the output file could not be created, the test is aborted. That is, overlay generation failure is a fatal error.

= RETURN =
Returns non-zero on error.

= SOURCE =
Located in ''scripts/overlays.sh''

= SEE ALSO =
 * [[ovgen.py]], [[functional.sh]], [[benchmark.sh]]