Using "path.Base", "path.Dir", and "path.Ext" to examine path and filename components | CUE

Jonathan Matthews

commented cue

This Commented CUE demonstrates how to use the built-in functions path.Base, path.Dir, and path.Ext to access components of a file’s name and its path.

package example

import "path"

[X=string]: {
	_OS: *path.Unix | path.Windows | path.Plan9
	Dir:  path.Dir(X, _OS)
	Base: path.Base(X, _OS)
	Ext:  path.Ext(X, _OS)
}

// Examples of absolute paths.
"/foo/bar/baz.js": _
#"C:\foo\bar\baz.js"#: _OS: path.Windows

// Examples of directory traversal.
"foo/bar/../quux/a.js": _
#"C:\foo\bar\..\quux\a.js"#: _OS: path.Windows

// Examples of empty path components.
"/foo///bar////baz.js": _
#"C:\foo\\bar\\\baz.js"#: _OS: path.Windows

$ cue eval
"/foo/bar/baz.js": {
    Dir:  "/foo/bar"
    Base: "baz.js"
    Ext:  ".js"
}
"C:\\foo\\bar\\baz.js": {
    Dir:  "C:\\foo\\bar"
    Base: "baz.js"
    Ext:  ".js"
}
"foo/bar/../quux/a.js": {
    Dir:  "foo/quux"
    Base: "a.js"
    Ext:  ".js"
}
"C:\\foo\\bar\\..\\quux\\a.js": {
    Dir:  "C:\\foo\\quux"
    Base: "a.js"
    Ext:  ".js"
}
"/foo///bar////baz.js": {
    Dir:  "/foo/bar"
    Base: "baz.js"
    Ext:  ".js"
}
"C:\\foo\\\\bar\\\\\\baz.js": {
    Dir:  "C:\\foo\\bar"
    Base: "baz.js"
    Ext:  ".js"
}

The path built-in package documentation details the rules that each of the functions path.Base, path.Dir, and path.Ext follow as they process their input
Using CUE’s “raw” strings is convenient when writing literal Windows paths. They avoid having to escape every backslash (\\), as is demonstrated in the Windows-related examples above.

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