Prototypes for initialization of directory search path module. Using the
subroutines in this file you can:
. Add the directories of one path to another path.
. Add directories represented by strings to a path.
. Add directories represented by environment variable strings to a path.
. Retrieve the name of the current directory (with respect to an internal
index) in a path.
. Return the number of directories in a path.
. Return the index of the current directory in a path.
. Extract the directories from a path.
. Get the nth (as specified by index) directory from a path.
. Retrieve the name of the previous directory (with respect to an internal
index) in a path.
. Create a path from directories represented by strings.
. Find the first file with a specific name in a path.
. Prepare to index through each directory in a path.