Behavior of this task depends upon the value of the PFILES environment variable, which is used to specify the location of parameter files. The PFILES variable uses a semicolon delimiter to separate two types of parameter directories:
<user>;<system>
The first path ("user") is one or more "local" (writeable) parameter
directories (typically $HOME/pfiles for a default HEASoft setup),
and the second path ("system") is one or more read-only parameter
directories (typically $HEADAS/syspfiles). When both paths are
equivalent, one may omit the semicolon and duplicate path (for
example, when developing a new task, one might set PFILES="." to
use only the current working directory). Multiple colon-delimited
directories are allowed in both portions of the PFILES variable:
<user1>:<user2>;<system1>:<system2>
The default values from the first "system" path are used the first
time a task is run, or whenever the default values have been updated
more recently than the user's copy of the parameters. The user's
copy is created when a task terminates, and retains any learned
changes to the parameters.
This task will look for a copy of the specified parameter file (or parameter file for the specified task) in the first "system" parameter directory; if the file does not exist there, it will then search all subsequent "system" directories listed in PFILES.
The "-f" flag may be used to disable searching of directories listed in the PFILES variable, allowing instead for specification of a particular parameter file (with a preceding directory path if the file is not in the current working directory).
% punlearn ftverifyor
% punlearn ftverify.par2. Unlearn the parameters for ftverify, disabling the default search of system directories listed in PFILES and instead providing the path to a specific parameter file:
% punlearn -f /local/data/test/ftverify.par