Validate String input COULD be a valid path

Question

I wish to validate a string path. I don't want to check that the path exists or create the path (that includes create + then delete), I simply wish to check that the input string COULD be a validate path on the executing system.

So far I have been messing with the File class with no luck. I would expect the following to fail on my OSX machine but it doesn't:

File f = new File("!@£$%^&*()±§-_=+[{}]:;\"'|>.?/<,~`±");
System.out.println(f.getCanonicalPath());

Is there anything that will do this for me?

`I simply wish to check that the input string COULD be a validate path on the executing system.` What's the end goal? — Sotirios Delimanolis, Jun 27 '14 at 21:26
@SotiriosDelimanolis - to validate the user has actually inputted something which adheres to the operating system's rules of how a path can be constructed. — Cheetah, Jun 27 '14 at 21:28
@SotiriosDelimanolis - oh my, I stand corrected, I thought that would be invalid - its not!! — Cheetah, Jun 27 '14 at 21:41
There's very little that isn't allowed in a file name, on unix systems at least. — Sotirios Delimanolis, Jun 27 '14 at 21:42
@SotiriosDelimanolis - added a definitely invalid example :) — Cheetah, Jun 27 '14 at 21:45

score 0 · Answer 1 · edited May 23 '17 at 12:11

0

You can do it via regex: File path validation in javascript

Or by checking if the parent of the path exists: Is there a way in Java to determine if a path is valid without attempting to create a file?

Just note that the path depends on the OS: https://serverfault.com/questions/150740/linux-windows-unix-file-names-which-characters-are-allowed-which-are-unesc

Also, just because the path is valid, it doesn't mean the file can be written there. For example, in Linux, you need to be a super user to write to /usr/

edited May 23 '17 at 12:11

Community

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answered Jun 27 '14 at 21:30

Alexandre Santos

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Please don't put link only answers. – Sotirios Delimanolis Jun 27 '14 at 21:34

score 0 · Answer 2 · answered Jun 27 '14 at 21:30

You could choose to use regex to check the path. Regex would look like:

^(?:[a-zA-Z]\:|\\\\[\w\.]+\\[\w.$]+)\\(?:[\w]+\\)*\w([\w.])+$

And an example can be seen here at Regexr. You can check this in Java using the String.matches(regex) function. An example below:

public static void main(String[] args) throws Exception {

    String regex = "^(?:[a-zA-Z]\\:|\\\\\\\\[\\w\\.]+\\\\[\\w.$]+)\\\\(?:[\\w]+\\\\)*\\w([\\w.])+$";
    String path = "c:\\folder\\myfile.txt";

    System.out.println(path.matches(regex));

}

(Note that the regex looks significantly longer due to having to escape the \ characters). Just call yourPathString.matches(regex), and it will return true if it is a valid path.

This looks like a windows only solution. I need platform independence. — Cheetah, Jun 27 '14 at 21:55
It matches linux/Mac paths as well. Check the regexr demo and test the paths you are trying to match. — Mike Elofson, Jun 27 '14 at 22:41

martinez314 · Answer 3 · 2014-06-27T21:44:44.893

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If the path is valid, then at least one of the chain of parent files must exist. If no parent exists, then it must be invalid.

public static boolean isValidPath(File file) throws IOException {
    file = file.getCanonicalFile();

    while (file != null) {
        if (file.exists()) {
            return true;
        }

        file = file.getParentFile();
    }

    return false;
}

System.out.println(isValidPath(new File("/Users/something")));  // true (OS X)
System.out.println(isValidPath(new File("asfq34fawrf")));  // false

edited Jun 27 '14 at 21:44

answered Jun 27 '14 at 21:36

martinez314

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What if it's a relative path? – Sotirios Delimanolis Jun 27 '14 at 21:39
@SotiriosDelimanolis I edited the answer. It would need to be converted to an absolute path. – martinez314 Jun 27 '14 at 21:45
With your solution, if it is a relative path, it is resolved against the current working directory. It will then be valid, since the parent file exists, since the pwd exists. Even if the file name is not acceptable. – Sotirios Delimanolis Jun 27 '14 at 21:48
This FAILS on my example in the OP regardless of whether its an absolute or relative path. – Cheetah Jun 27 '14 at 21:54

Validate String input COULD be a valid path

3 Answers3