Pathnames are immutable record-style objects of a disjoint type that represent the natural components of (string) filenames in a way that is intended to be system-independent. This design is mostly based on MIT Scheme, which is mostly based on Common Lisp. However, it is extended to accept additional components which are required to represent URIs and IRIs as well as filenames. In addition, given the pervasiveness of Windows and Posix filenames nowadays, specific provisions for them has been made.
The components of a pathname are scheme, host, port, username, password, device, directory, name, type, version, query, and fragment.
Scheme is the scheme part of a URI/IRI. It is a string.
Username is the username associated with a URI/IRI host. It is a string.
Password is the password associated with a username. It is a string.
Host is the host part of a URI/IRI, the server part of a UNC name, or the host part of a Berkeley-style host:pathname. It is a string.
Port is the port part of a URI/IRI. It is an exact integer.
Device is a Windows-style device name without a trailing colon. It is a string, typically but not always a single character.
Directory is a directory path, which is represented as a list. The first element is always a symbol, either absolute or relative, representing pathnames relative to the system root or the current directory respectively. The root directory is represented by the list (absolute). A null directory path is represented by the empty list. The other elements are strings.
Name is a simple file name without the associated file type or extension, if any. It is a string.
Type is the type or extension of the filename, without any leading period. It is a string.
Version specifies the version of a file. It is normally an exact positive integer, where 1 represents the oldest possible version. The symbols oldest and newest represent the oldest and newest existing versions.
Query is the query part of a URI/IRI. It may be an a-list mapping strings to strings, or a simple string.
Fragment is the fragment part of an IRI/URI. It is a string.
All of these components can also be #f to indicate that the component is not present.
The procedures pathname? and pathname=? do what you expect. Note that two pathnames may be different according to pathname=? but still access the same resource. Host components are compared case-insensitively.
There are twelve accessors corresponding to the twelve components of a pathname, which take the form pathname-* where * is one of the components.
(pathname-query-as-string pathname)
Returns the query component as a string. If it is already a string, the string is returned. If it is an a-list, the a-list is converted into a string containing name-value pairs separated by & and with = between the name and the value.
(pathname-directory-as-string pathname options)
Returns the directory component as a string. Options is a list of symbols that may contain windows; if it contains other symbols, the result is implementation-specified. The result consists of the strings in the cdr of the directory component joined using the path separator, with the separator prepended if the car is absolute. If windows is present in options, the path separator is \; otherwise, the path separator is '/'.
It is an error to mutate anything returned by any of these accessors.
(make-pathname components)
Constructs and returns a pathname. Components is an a-list mapping component names to values. Component names not defined in this specification are allowed, but the results are implementation-specific. Any component names not appearing in components are set to #f.
The following procedures accept a string and construct and return a pathname corresponding to that string.
(filename->pathname filename options)
Constructs and returns a pathname. Filename is a string to be converted to a filename. Options is a list of symbols that may include windows, version and/or host. Other symbols may be present, but the result is implementation-dependent.
If version is present in options, then if filename ends in .~n~, where n is a positive integer, then that suffix is stripped off and the version component is set to n. Otherwise, if filename ends in ~, then it is stripped off and the version' component is set to oldest. Otherwise, or if version is not present, then the version component is set to newest.
If windows is not present and host is present, and there is a colon in filename, then the portion before the colon is stripped off and used to populate the host component. If windows is present and filename begins with \\ or //, its first portion is stripped off and used to populate the host component. Otherwise, the host component is set to "localhost".
If windows is not present in options, then filename is parsed using / as the component separator, and the directory, name, and type components are potentially populated from it, and the device component is set to #f. But if windows is present, then filename is parsed using both \ and / as component separators, and the device, directory, name, and type components are potentially populated from it.
Finally, the scheme component is set to "file", and the username, password, port, query, and fragment components are set to #f.
(uri->pathname uri)
Constructs and returns a pathname. Uri is a string to be converted to a pathname. It is parsed according to IRI rules, which are the same as URI rules except that sequences of %-hexdigit-hexdigit escapes that represent UTF-8 byte sequences are parsed into characters, provided the requisite characters are supported by the implementation.
The scheme, host, port, username, password, directory, name, type, query, and fragment components are potentially populated from uri. The device and version components are set to #f. If the query part of the IRI consists of name-value pairs separated by & or ; and with = between the name and the value, then the query component will be an a-list of strings; otherwise, it will just be a string.
The following procedures accept a pathname and construct and return a string corresponding to that pathname.
(pathname->filename pathname options)
Constructs and returns a string from pathname. Options is a list of symbols that may include windows, version and/or host; however, version and host are ignored. Other symbols may be present, but the result is implementation-dependent.
If windows is not present in options, then the result is constructed using / as the component separator from the directory (using directory-as-string), name, and type components of pathname, and if the host component is not #f or "localhost", then its value and a colon are prepended to the result. But if windows is present, then the result is constructed using \ as the component separator from the host, device, directory (using directory-as-string), name, and type components.
If the version component is an exact positive integer n, then .~n~ is appended to the result. Otherwise, if the version component is oldest, then ~ is appended to the result.
It is an error if the scheme component is not set to "file", or the username, password, port, query, and fragment components are not #f.
(pathname->uri pathname)
Constructs and returns a string according to RFC 3986 rules. In addition to required %-escaping, non-ASCII characters are converted to UTF-8 byte strings and %-escaped.
The scheme, host, port, username, password, directory (using directory-as-string), name, type, query (using query-as-string), and fragment components are used to construct the URI. It is an error if the device and version components are not #f.
(pathname->iri pathname)
Constructs and returns a string according to RFC 3987 rules. No escaping of non-ASCII characters is done.
The scheme, host, port, username, password, directory (using directory-as-string), name, type, query (using query-as-string), and fragment components are used to construct the URI. It is an error if the device and version components are not #f.
(merge-pathnames pathname1 pathname2)
Constructs and returns a new pathname with the same components as pathname1. However, if any component of pathname1 is #f, the corresponding component of pathname2 is used instead. The directory component is handled specially; if the pathname1 component begins with relative, the rest of it is appended to the pathname2 component. Similarly, if the query components are both a-lists, the a-list of pathname1 is prepended to the a-list of pathname2.
(pathname-absolute-filename? pathname options)
Returns #t if pathname specifies an absolute filename. If windows is contained in options, that means the device component must be specified.
(pathname-absolute-uri? pathname options)
Returns #t if pathname specifies an absolute URI.
(pathname-uri? pathname options)
Returns #t if pathname specifies a URI/IRI (that is, pathname specifies an absolute URI and the fragment component is #f).