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c#windowscommand-prompt
John Hodge
John Hodge

Reputation: 1715

What are the consequences, if any, of multiple backslashes in Windows paths?

In my programs I frequently have file names and/or paths that are configured in my app.config file. This will usually be something like:

<add key="LogFileDirectory" value="C:\Logs" />
<add key="SaveLogFileTo" value="MyLogFile.txt" />

In my actual application code, I'll frequently concatenate these together with code similar to this:

var logFile = ConfigurationManager.AppSettings["LogFileDirectory"]
+ @"\" +
ConfigurationManager.AppSettings["SaveLogFileTo"];

Now, the result of the above code would give a log file path of C:\Logs\MyLogFile.txt, however, if the end-user specifies the log file directory in the configuration file as C:\Logs\ with a trailing backslash, my code results in an actual path of C:\Logs\\MyLogFile.txt with a double backslash between the directory and the file.

In my experience, this works just fine in practice. As a matter of fact, even dropping to a command prompt and executing cd c:\\\\\\windows\\\ works in practice.

My question is, what, if any, are the consequences of having paths like this? I don't want to be using this "feature" in production code if it is something that is undocumented and subject to be broken at some point in the future with a new release of Windows.

Upvotes: 3

Views: 2476

Answers (2)

Jari Kulmala
Jari Kulmala

Reputation: 69

At least these kind of consequences there are:

del command cannot delete the file if you provide two backslashes after the drive letter and colon:

C:\>del c:\\foo.txt
The filename, directory name, or volume label syntax is incorrect.

C:\>del c:\\bar\foo.txt
The network path was not found.

I mean, according to my experiments, the cmd.exe built in "del" command has a bug that tries to access a network share instead.

The bug is dangerous actually. The del command believes that c:\\bar\foo\zap.txt means \\bar\foo\zap.txt and if there really is a server "bar" that has share "foo" that has file "zap.txt", an incorrect file will be deleted if you meant a local file c:\bar\foo\zap.txt instead.

I do not know that other commands would behave this way. For example the built in type and copy commands ignore the duplicate backslash and refer to local file.

Upvotes: 0

Blorgbeard
Blorgbeard

Reputation: 103467

There are no consequences that I know of, and it's not likely to be broken in future versions, because a lot of people will be doing the same as you.

However, the correct way to combine paths in C# is to use Path.Combine, which will remove any extra backslashes for you:

var logFile = Path.Combine(
    ConfigurationManager.AppSettings["LogFileDirectory"],
    ConfigurationManager.AppSettings["SaveLogFileTo"]);

Upvotes: 3

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