Emacs正则表达式中的字符串的开头和结尾 [英] Beginning and end of the string in Emacs regexps

问题描述

我正在编写一个修剪函数：

What is the characters that indicate the beginning and the end of the string with newlines in it? I'm writing a trim function:

(defun trim (str)
  (if (string-match "^[[:space:]]*\\(.+?\\)[[:space:]]*$" str)
      (match-string 1 str)
      str))

但是使用first / nnext（从 shell获取） -command-to-string ）它只返回第一个。参考手册说：

But with a string like "first/nnext" (got from shell-command-to-string) it returns only the "first". Reference manual says:

当匹配字符串而不是缓冲区时，'^'在
字符串的开头匹配，或在换行符后。

When matching a string instead of a buffer, ‘^’ matches at the beginning of the string or after a newline character.

\\'而左侧是用于缓冲区的开始/结束，所以它只是从字符串返回任何东西。因此，如果可能，如何指示字符串的绝对开始？

\\' and the left one are for beginning/end of a buffer, so it simply returns nothing from a string. Therefore, how to indicate the 'absolute' beginning of a string, if possible?

推荐答案

它是 \\\` 用于开始缓冲区或字符串。而 \\'为结束。请参阅手册

It's \\` for beginning of buffer or string. And \\' for end. See manual

但是，我认为你的耻辱的根源不是锚点。 char类根据当前语法表匹配不同的字符， [：space：] 要可靠地匹配非打印或打印字符，请使用 [：graph：] 。请参阅 char class

However, I think the root of your confustion isn't the anchor. The [:space:] char class matches different characters based on the current syntax table. To reliably match a non-printing or printing character use [:graph:]. See char class

另外。不会匹配换行符。

例如$（$）

E.g.

(let ((str " \n a\nbc \n "))
  (string-match "\\`[^[:graph:]]*\\(\\(?:.\\|\n\\)+?\\)[^[:graph:]]*\\'" str)
  (match-string 1 str))

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