Pathname expansion

Shell-style homedir expansion in path names.

This egg serves as a partial replacement of the historical expansion behaviour of all file operations in CHICKEN core: strings prefixed with a tilde are expanded into home directories, but strings prefixed with a dollar sign are not expanded into environment variables.

Author

The CHICKEN Team

Requirements

None

Documentation

[procedure] (pathname-expand STRING #!optional BASE)

If STRING is identical to "~" or if it begins with "~/", return the argument with the "~" substituted by the current user's home directory. If the current user cannot be determined or does not exist, a condition of type (exn pathname-expand username) is raised.

If STRING begins with "~USERNAME", return the argument with the "~USERNAME" substituted by the provided user's HOME directory. On Windows, this will be the value of the environment variables USERPROFILE or HOME (or "." if none of the variables is set). On Unix systems, the user database is consulted. If the user does not exist, a condition of type (exn pathname-expand username) is raised.

If STRING is identical to "~~" or if it begins with "~~/", return the argument with the "~~" substituted by (repository-path). If there is no repository path, a condition of type (exn pathname-expand repository-path) is raised.

If STRING doesn't begin with a tilde, and it represents an absolute pathname, then it is returned unchanged. If instead it is a relative pathname the result of (make-pathname STRING BASE) is returned, where BASE defaults to the current working directory.

Known bugs and limitations

The concept of pathname expansion is fuzzy and ill-defined. It boils down to "do what I mean". Because of this, in situations where security is a concern this egg should be used with great care.

Furthermore, the exact expansion rules differ across shells, and it's unclear exactly how it should behave under non-UNIX operating systems.

Changelog

0.1 Initial release

License

 
 Copyright (c) 2014, The CHICKEN Team
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