问题
I'm currently trying to encode a string for insertion into a URL. My issue is that this seems to fail when my string contains a backslash. I've tried 4 approaches so far using the URLencode, curlEscape (from RCurl), and curlPercentEncode (from RCurl) functions, but none of them have been successful.
> URLencode("hello\hello")
Error: '\h' is an unrecognized escape in character string starting ""hello\h"
> curlEscape("hello\hello")
Error: '\h' is an unrecognized escape in character string starting ""hello\h"
> curlPercentEncode("hello\hello")
Error: '\h' is an unrecognized escape in character string starting ""hello\h"
> curlPercentEncode("hello\hello", amp=TRUE)
Error: '\h' is an unrecognized escape in character string starting ""hello\h"
回答1:
You are looking for
> URLencode("hello\\hello")
[1] "hello%5chello"
The error you're getting is not from any of the functions you tried to call; it didn't get as far as actually calling any of them. The error is from R's parser. Backslash is a special character for string literals themselves, so you need to write a double backslash in your string literal in order to produce a string value containing a backslash. (There are several other things you can usefully put after the backslash; for instance, "\"" is how you write a string value consisting of one double-quote character. Read ?Quotes for further information.)
Since this is an issue with the syntax of string literals, it shouldn't come up if you're reading the "string for insertion into a URL" from a data source; it should only be an issue if you need to write this string directly in your code.
来源：https://stackoverflow.com/questions/26304172/how-to-url-encode-a-backslash-with-r-rcurl