[r6rs-discuss] [Formal] Please give us file-exists? and delete-file.

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Submitter: William D Clinger
Email address: will_at_ccs.neu.edu
Issue type: Enhancement
Priority: Minor
Component: I/O
Report version: 5.91
Summary: Please give us file-exists? and delete-file.
Full description of issue:
Programs often need to determine whether a file exists,
and programs also need to clean up after themselves by
deleting files.
The draft R6RS does not provide any way to delete a file.
The draft R6RS provides facilities that may be adequate
for determining whether a file exists: the program would
establish an exception handler for &i/o-file-exists-not
conditions, try to open the file for input, and conclude
that the file exists if and only no exception is raised.
That technique is inconvenient, might be inefficient, and
might be viewed as misuse of the exception system, whose
stated purpose is to deal with exceptional situations;
when searching several paths for an optional input or
configuration file, the existence of that file is more
exceptional than its non-existence.
Current practice:
Of ten implementations surveyed, nine (Bigloo, Chicken,
Gambit, Kawa, Larceny, MIT Scheme, MzScheme, Petite Chez,
and scm) supply file-exists? and delete-file as part of
their default runtime.  Only one (Scheme 48) does not.
A grep of Larceny's code base found more than a hundred
uses of file-exists?, and more than a hundred uses of
delete-file.  A comparable number of uses were found in
Gambit's code base.
Related issues:
Programs also need to determine whether a directory exists,
and to iterate through the files that are contained within
a directory.  I do not know whether these features are as
ready for standardization as file-exists? and delete-file.
[end of comment]