Apache – Are square brackets permitted in URLs

apachehttpsquare-bracketsyntaxurl

Are square brackets in URLs allowed?

I noticed that Apache commons HttpClient (3.0.1) throws an IOException, wget and Firefox however accept square brackets.

URL example:

http://example.com/path/to/file[3].html

My HTTP client encounters such URLs but I'm not sure whether to patch the code or to throw an exception (as it actually should be).

Best Answer

RFC 3986 states

A host identified by an Internet Protocol literal address, version 6 [RFC3513] or later, is distinguished by enclosing the IP literal within square brackets ("[" and "]"). This is the only place where square bracket characters are allowed in the URI syntax.

So you should not be seeing such URI's in the wild in theory, as they should arrive encoded.

Related Solutions

C# – Path.Combine for URLs

Uri has a constructor that should do this for you: new Uri(Uri baseUri, string relativeUri)

Here's an example:

Uri baseUri = new Uri("http://www.contoso.com");
Uri myUri = new Uri(baseUri, "catalog/shownew.htm");

Note from editor: Beware, this method does not work as expected. It can cut part of baseUri in some cases. See comments and other answers.

Bash – Is double square brackets [[ ]] preferable over single square brackets [ ] in Bash

[[ has fewer surprises and is generally safer to use. But it is not portable - POSIX doesn't specify what it does and only some shells support it (beside bash, I heard ksh supports it too). For example, you can do

[[ -e $b ]]

to test whether a file exists. But with [, you have to quote $b, because it splits the argument and expands things like "a*" (where [[ takes it literally). That has also to do with how [ can be an external program and receives its argument just normally like every other program (although it can also be a builtin, but then it still has not this special handling).

[[ also has some other nice features, like regular expression matching with =~ along with operators like they are known in C-like languages. Here is a good page about it: What is the difference between test, [ and [[ ? and Bash Tests

Best Answer

Related Solutions

C# – Path.Combine for URLs

Bash – Is double square brackets [[ ]] preferable over single square brackets [ ] in Bash

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