library file search order

When searching for a file specified on the libfile option, directories are searched in the following order:

1. Current directory

2. Directories specified by using the libdirectory option

3. default directories

   1. Directory specified by environment variable LNCOP, if it exists

   2. Directory specified by environment variable COP, if it exists

   3. Directory \COP

If the xdirectory option is specified, only directories specified by using the libdirectory option are searched.

Any filename that contains an explicit directory is checked for only in that directory. No other directories are searched.