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https://issues.apache.org/jira/browse/IO-860?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17892624#comment-17892624
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Stefan Feenstra commented on IO-860:
------------------------------------
Also not sure about one further discrepancy.
According to the same documentation a filename should not end with a dot.
In practice, it appears that applications like Java, windows file explorer etc
will allow you to open or save a file with a dot at the end - however the
created/read file will not contain the dot at the end of the filename,
In fact, if a file is present on the disk ending with a dot (This can be done
by using the \\?\ prefix) most APIs will say the file does not exist when
trying to open it.
I am not sure if Commons IO should mark these filenames as invalid? This could
potentially cause problems in applications?
Example code:
{code:java}
System.out.println("test.txt. exists: " + new
File("test.txt.").exists());
System.out.println("test.txt exists: " + new File("test.txt").exists());
try (FileOutputStream fos = new FileOutputStream("test.txt.")) {
fos.write("test".getBytes());
}
System.out.println("test.txt. exists: " + new
File("test.txt.").exists());
System.out.println("test.txt exists: " + new File("test.txt").exists());
{code}
One would expect only the first file to exist after the code is ran, the actual
output is however:
{code}
test.txt. exists: false
test.txt exists: false
test.txt. exists: true
test.txt exists: true
{code}
> Missing reserved filenames for Windows in FileSystem.java (superscript digits
> for COM and LPT)
> -----------------------------------------------------------------------------------------------
>
> Key: IO-860
> URL: https://issues.apache.org/jira/browse/IO-860
> Project: Commons IO
> Issue Type: Bug
> Components: Utilities
> Affects Versions: 2.17.0
> Reporter: Stefan Feenstra
> Priority: Major
>
> Per Microsoft documentation, the following filenames are also reserved
> filenames: LPT¹, LPT², LPT³, COM¹, COM² and COM³.
> As far as I can tell, only the non-superscript filenames are marked as
> illegal in the FileSystem.WINDOWS enum. These six filenames should also be
> added as reserved filenames, as they can not be used for regular files. (e.g.
> trying to create a file called COM³ will fail).
>
> Quote from the [microsoft
> documentation|https://learn.microsoft.com/en-us/windows/win32/fileio/naming-a-file#file-and-directory-names]:
> {code:java}
> Windows recognizes the 8-bit ISO/IEC 8859-1
> superscript digits ¹, ², and ³ as digits and treats them as valid parts
> of COM# and LPT# device names, making them reserved in every directory.
> {code}
> Testing code to reproduce: (there should be no output)
> {code:java}
> import org.apache.commons.io.FileSystem;
> public class FilenameTest {
> public static void main(String[] args) {
> char[] digitsWithSuperScript = {'1', '2', '3', '4', '5', '6', '7',
> '8', '9', '¹', '²', '³'};
> for (String filenamesPrefix : new String[]{"LPT", "COM"}) {
> for (char digit : digitsWithSuperScript) {
> final String filename = filenamesPrefix + digit;
> checkFilename(filename, true);
> // Base filename should be reserved
> checkFilename(filename + ".tar.gz", true);
> // Extensions should be ignored
> checkFilename(filename + ".txt", true);
> // Non-extension suffixes are ok.
> checkFilename(filename + "additional_text", false);
> }
> }
> for (String reservedFileName : new String[]{"CON", "PRN", "AUX",
> "NUL", "CONIN$", "CONOUT$"}) {
> // Base filename should be reserved
> checkFilename(reservedFileName, true);
> // Extensions should be ignored
> checkFilename(reservedFileName + ".tar.gz", true);
> // Non-extension suffixes are ok.
> checkFilename(reservedFileName + "additional_text", false);
> }
> }
> static void checkFilename(String filename, boolean isReserved) {
> boolean isReservedAccordingToAPI =
> FileSystem.WINDOWS.isReservedFileName(filename);
> if (isReserved != isReservedAccordingToAPI) {
> if (isReserved) {
> System.out.printf("'%s' is reserved according to the spec but
> not according to FileSystem.isReservedFileName%n", filename);
> } else {
> System.out.printf("'%s' is not reserved according to the spec
> but is according to FileSystem.isReservedFileName%n", filename);
> }
> } else {
> // Spec and API match
> }
> }
> }{code}
>
> Link to relevant code:
> [https://github.com/apache/commons-io/blob/ec0fd2c98f0bf94d6d87c6adf237430e606e2e23/src/main/java/org/apache/commons/io/FileSystem.java#L91C16-L92C116]
>
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