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Given a Java 'File' object, how can I detect whether or not it refers to a symlink?

(If it helps/matters, I know the file refers to a directory, not to a file)

Matt Sheppard
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2 Answers2

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File.getCanonicalPath() resolves symlinks

A canonical pathname is both absolute and unique. The precise definition of canonical form is system-dependent. This method first converts this pathname to absolute form if necessary, as if by invoking the getAbsolutePath() method, and then maps it to its unique form in a system-dependent way. This typically involves removing redundant names such as "." and ".." from the pathname, resolving symbolic links (on UNIX platforms), and converting drive letters to a standard case (on Microsoft Windows platforms).

I assume you can compare the result of getCanonicalPath() and getAbsolutePath().

Update: It appears this question has already been asked - check the answers there

Community
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Bozho
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    Sounds like it might work - I wonder how expensive it is to call on a real file-system object (I assume it's having to check each directory up the tree, where as I only care about the last one)... – Matt Sheppard Mar 22 '10 at 06:46
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    Thanks - Using Apache's commons IO as noted in http://stackoverflow.com/questions/813710/java-1-6-determine-symbolic-links/813730#813730 seems like a good solution. – Matt Sheppard Mar 22 '10 at 23:56
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Also you can use isSymbolicLink(Path path) method. It will be more reliable.

java.io.File file = ...;
boolean isSymbolicLink = Files.isSymbolicLink(file.toPath());

Similar examples from Java Doc 'Detecting a Symbolic Link'.

Wayne
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  • There's a caveat - like `Files.exists`, `Files.isSymbolicLink` can sometimes return a false negative. – Hakanai Jul 29 '21 at 23:34
  • @Hakanai could you provide an example? – auraham Aug 11 '22 at 21:54
  • @auraham if an exception occurs when checking for the information, the method will swallow the exception and return false, regardless of whether the file is a symbolic link. Because of that, in many cases, for `Files.exists()`, what you often really want is `!Files.notExists()`. But it wasn't the case 100% of the time either. This mess caused us to ban usage of the methods in our codebase, redirecting calls to our own versions which throw the exception. – Hakanai Aug 16 '22 at 08:02