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2.16.4 Search Lists

Search lists are an extension to Common Lisp pathnames. They serve a function somewhat similar to Common Lisp logical pathnames, but work more like Unix PATH variables. Search lists are used for two purposes:

• They provide a convenient shorthand for commonly used directory names, and
• They allow the abstract (directory structure independent) specification of file locations in program pathname constants (similar to logical pathnames.)

Each search list has an associated list of directories (represented as pathnames with no name or type component.) The namestring for any relative pathname may be prefixed with “slist:”, indicating that the pathname is relative to the search list slist (instead of to the current working directory.) Once qualified with a search list, the pathname is no longer considered to be relative.

When a search list qualified pathname is passed to a file-system operation such as open, load or truename, each directory in the search list is successively used as the root of the pathname until the file is located. When a file is written to a search list directory, the file is always written to the first directory in the list.