I was thinking about Registering an Application to a URL Protocol and I'd like to know, what characters are allowed in a scheme?
Some examples:
- h323 (has numbers)
h323:[<user>@]<host>[:<port>][;<parameters>]
- z39.50r (has a
.as well)z39.50r://<host>[:<port>]/<database>?<docid>[;esn=<elementset>][;rs=<recordsyntax>]
- paparazzi:http (has a
:)paparazzi:http:[//<host>[:[<port>][<transport>]]/
So, what characters can I fancy using?
Can we have...
@:TwitterUser#:HashTag$:CapitalStock?:ID-10T
...etc., as desired, or characters in the scheme are restricted by standard?
According to RFC 2396, Appendix A:
scheme = alpha *( alpha | digit | "+" | "-" | "." )
Meaning:
The scheme should start with a letter (upper or lower case), and can contains letters (still upper and lower case), number, "+", "-" and ".".
Note: in the case of
paparazzi:http:[//<host>[:[<port>][<transport>]]/
the scheme is only the "paparazzi" part.
The scheme according to RFC 3986 is defined as:
scheme = ALPHA *( ALPHA / DIGIT / "+" / "-" / "." )
So the scheme must begin with an alphabetic character (A–Z, a–z) and may be followed by any number of alphanumeric characters, +, -, or ..
Quoth RFC 2396:
Scheme names consist of a sequence of characters beginning with a lower case letter and followed by any combination of lower case letters, digits, plus ("+"), period ("."), or hyphen ("-").
来源：https://stackoverflow.com/questions/3641722/valid-characters-for-uri-schemes