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== Unit files

This unit contains file- and pathname-oriented procedures. It uses the {{regex}} unit.


=== Pathname operations

==== absolute-pathname?

<procedure>(absolute-pathname? PATHNAME)</procedure>

Returns {{#t}} if the string {{PATHNAME}} names an absolute
pathname, and returns {{#f}} otherwise.

==== decompose-pathname

<procedure>(decompose-pathname PATHNAME)</procedure>

Returns three values: the directory-, filename- and extension-components
of the file named by the string {{PATHNAME}}.
For any component that is not contained in {{PATHNAME}}, {{#f}} is returned.

==== make-pathname
==== make-absolute-pathname

<procedure>(make-pathname DIRECTORY FILENAME [EXTENSION])</procedure><br>
<procedure>(make-absolute-pathname DIRECTORY FILENAME [EXTENSION])</procedure>

Returns a string that names the file with the
components {{DIRECTORY, FILENAME}} and (optionally)
{{EXTENSION}} with {{SEPARATOR}} being the directory separation indicator
(usually {{/}} on UNIX systems and {{\}} on Windows, defaulting to whatever
platform this is running on). 
{{DIRECTORY}} can be {{#f}} (meaning no
directory component), a string or a list of strings. {{FILENAME}}
and {{EXTENSION}} should be strings or {{#f}}.
{{make-absolute-pathname}} returns always an absolute pathname.

==== pathname-directory
==== pathname-file
==== pathname-extension

<procedure>(pathname-directory PATHNAME)</procedure><br>
<procedure>(pathname-file PATHNAME)</procedure><br>
<procedure>(pathname-extension PATHNAME)</procedure>

Accessors for the components of {{PATHNAME}}. If the pathname does
not contain the accessed component, then {{#f}} is returned.

==== pathname-replace-directory
==== pathname-replace-file
==== pathname-replace-extension

<procedure>(pathname-replace-directory PATHNAME DIRECTORY)</procedure><br>
<procedure>(pathname-replace-file PATHNAME FILENAME)</procedure><br>
<procedure>(pathname-replace-extension PATHNAME EXTENSION)</procedure>

Return a new pathname with the specified component of {{PATHNAME}}
replaced by a new value.

==== pathname-strip-directory
==== pathname-strip-extension

<procedure>(pathname-strip-directory PATHNAME)</procedure><br>
<procedure>(pathname-strip-extension PATHNAME)</procedure>

Return a new pathname with the specified component of {{PATHNAME}}
stripped.

==== normalize-pathname

<procedure>(normalize-pathname PATHNAME [PLATFORM])</procedure>

Performs a simple "normalization" on the {{PATHNAME}}, suitably for
{{PLATFORM}}, which should be one of the symbols {{windows}}
or {{unix}} and defaults to on whatever platform is currently
in use. All relative path elements and duplicate separators are processed 
and removed.  If {{NAME}} ends with
a {{/}} or is empty, the appropriate slash is appended to the tail.
Tilde {{~}} and variable {{$<name>/...}} expansion is also done.

No directories or files are actually tested for existence; this 
procedure only canonicalises path syntax.

==== directory-null?

<procedure>(directory-null? DIRECTORY)</procedure>

Does the {{DIRECTORY}} consist only of path separators and the period?

{{DIRECTORY}} may be a string or a list of strings.

==== decompose-directory

<procedure>(decompose-directory DIRECTORY)</procedure>

Returns 3 values: the {{base-origin}}, {{base-directory}}, and the
{{directory-elements}} for the {{DIRECTORY}}.

; {{base-origin}} : a {{string}} or {{#f}}. The drive, if any.
; {{base-directory}} : a {{string}} or {{#f}}. A directory-separator when {{DIRECTORY}} is an {{absolute-pathname}}.
; {{directory-elements}} : a {{list-of string}} or {{#f}}. The non-directory-separator bits.

{{DIRECTORY}} is a {{string}}.

* On Windows {{(decompose-directory "c:foo/bar")}} => {{"c:" #f ("foo" "bar")}}


=== Temporary files and directories

==== create-temporary-file

<procedure>(create-temporary-file [EXTENSION])</procedure>

Creates an empty temporary file and returns its pathname. If
{{EXTENSION}} is not given, then {{.tmp}} is used. If the
environment variable {{TMPDIR, TEMP}} or {{TMP}} is set,
then the pathname names a file in that directory. If none of
the environment variables is given the location of the
temporary file defaults to {{/tmp}} if it exists or the 
current-directory


==== create-temporary-directory

<procedure>(create-temporary-directory)</procedure>

Creates an empty temporary directory and returns its pathname. If the
environment variable {{TMPDIR, TEMP}} or {{TMP}} is set, then the
temporary directory is created at that location.


=== Deleting a file without signalling an error

==== delete-file*

<procedure>(delete-file* FILENAME)</procedure>

If the file {{FILENAME}} exists, it is deleted and {{#t}}
is returned.  If the file does not exist, nothing happens and {{#f}}
is returned.


=== File move/copy

==== file-copy

<procedure>(file-copy ORIGFILE NEWFILE #!optional CLOBBER BLOCKSIZE)</procedure>

Copies {{ORIGFILE}} (a string denoting some filename) to {{NEWFILE}}, 
{{BLOCKSIZE}} bytes at a time.  {{BLOCKSIZE}} defaults to 1024, and must be
a positive integer.  Returns the number of bytes copied on success, or errors
on failure.  {{CLOBBER}} determines the behaviour of {{file-copy}} when
{{NEWFILE}} is already extant.  When set to {{#f}} (default), an error is
signalled.  When set to any other value, {{NEWFILE}} is overwritten.
{{file-copy}} will work across filesystems and devices and is not
platform-dependent.

==== file-move

<procedure>(file-move ORIGFILE NEWFILE #!optional CLOBBER BLOCKSIZE)</procedure>

Moves {{ORIGFILE}} (a string denoting some filename) to {{NEWFILE}}, with
the same semantics as {{file-copy}}, above.  {{file-move}} is safe across
filesystems and devices (unlike {{file-rename}}).  It is possible for an
error to be signalled despite partial success if {{NEWFILE}} could be created
and fully written but removing {{ORIGFILE}} fails.

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