Question

我试图在字符串中获取\或/的位置。以下是我尝试的代码：

x <- "<span id=\"ref_12590587_l\">6,803.61</span>_l>"
gregexpr("\\\", x)
which(strsplit(x, "")[[1]]=="\")

我的问题是当我在Rstudio中尝试这些代码时，我得到一个继续提示，REPL提示变为+。这些代码适用于其他角色。

为什么我会收到继续提示，即使引号中引用了\？

编辑：在评论后更正了字符串。

Answer 1

你必须添加另一个斜杠（正如stribizhev在评论中所说）。所以你正在寻找

gregexpr("\\\\", x)

原因是你需要两次逃离\。所以\\只给你1个反斜杠。当你输入3时，第3个反斜杠实际上是在逃避引用！

参见示例：

gregexpr("\"", 'hello, "hello"')

这是在字符串中搜索引号。

Answer 2

Just to formalize my comments:

Your x variable does not contain any backslashes, these are escaping characters that allow us putting literal quotation marks into a string.
gregexpr("\\\", x) contains a non-closed string literal because the quotation mark on the right is escaped, and thus is treated as a literal quotation mark, not the one that is used to "close" a string literal.
To search for a literal \ in gregexpr, we need 4 backslashes \\\\, as gregexpr expects a regular expression. In regular expressions, "\" is a special symbol, thus it must be escaped for the regex engine. But inside gregexpr, we pass a string that itself is using \ for escaping entities like \n. So, we need to escape the backslash for R first, and then for the regex engine.

That said, you can use

gregexpr("\\\\", x)

to get only literal backslashes, or

gregexpr("\\\\|/", x)

to also look for forward slashes.