Bash =〜在cmd提示符OS X上丢失BASH_REMATCH内容 [英] Bash =~ loosing BASH_REMATCH contents at the cmd prompt OS X

问题描述

假设我有一个(愚蠢的示例)脚本:

Suppose I have a (silly example) script:

#!/bin/bash
st="one two three"
[[ $st =~ ^([[:alpha:]]+)[[:space:]]([[:alpha:]]+)[[:space:]]([[:alpha:]]+) ]]
for i in "${BASH_REMATCH[@]}"
do
    echo "$i"
done    

它按预期方式工作-打印:

It works as expected -- it prints:

one two three
one
two
three

然后是每个比赛组的整体比赛.但是，如果我进入shell并输入:

Which is the overall match then each match group. HOWEVER, if I go to the shell and type:

$ st="one two three"
$ [[ $st =~ ^([[:alpha:]]+)[[:space:]]([[:alpha:]]+)[[:space:]]([[:alpha:]]+) ]]
$ for i in "${BASH_REMATCH[@]}"
> do
>    echo "$i"
> done

它打印:

w

如果我这样做

$ [[ $st =~ ^([[:alpha:]]+)[[:space:]]([[:alpha:]]+)[[:space:]]([[:alpha:]]+) ]] && arr=( "${BASH_REMATCH[@]}" )

然后，我可以遍历 arr 中的 BASH_REMATCH 的副本，显示匹配正常.但是在Bash 3.2上使用交互式shell时， BASH_REMATCH 似乎发生了某些事情.比赛成功后.

I can then loop through the copy of BASH_REMATCH in arr showing that the match works OK. But something seems to happen to BASH_REMATCH in the interactive shell use on Bash 3.2. right after a successful match.

这是macOS Sierra 10.12.1上的默认 3.2.57(1)-发行版

This is the default 3.2.57(1)-release on macOS Sierra 10.12.1

如果我启动Bash 4.4，一切正常.

If I fire up Bash 4.4, it all works OK.

想法?

编辑

戈登·戴维斯是正确的:它与使用"$ {BASH_REMATCH [@]}" 的Apple实用程序有关，作为显示提示的一部分.

Gordon Davis is correct: it has to do with an Apple utility using "${BASH_REMATCH[@]}" as part of displaying the prompt.

易于演示:

$ cd ~
$ pwd && echo "${BASH_REMATCH[@]}"
/Users/andrew
w
$ cd /tmp
$ pwd && echo "${BASH_REMATCH[@]}"
/tmp
p

然后，如果我运行的苹果bash没有 rc 文件:

Then if I run Apple's bash with no rc file:

$ /bin/bash  --norc
bash-3.2$ pwd && echo "${BASH_REMATCH[@]}"
/tmp

bash-3.2$ 

(那里"$ {BASH_REMATCH [@]}" 的空白行...)

(There is a blank line for "${BASH_REMATCH[@]}" there...)

推荐答案

之所以会发生这种情况，是因为Apple的默认bash初始化文件具有精美的功能来定义提示，并且每次需要显示提示时都会重新计算该提示，并且该函数使用 =〜，因此替换了 BASH_REMATCH 的先前内容.参见/etc/bashrc_Apple_Terminal(由/etc/bashrc派生)中的 update_terminal_cwd 的定义.

This happens because Apple's default bash init file has a fancy function to define the prompt, and it recomputes it every time the prompt needs to be displayed, and that function uses =~ and therefore replaces the previous contents of BASH_REMATCH. See the definition of update_terminal_cwd in /etc/bashrc_Apple_Terminal (which is sourced by /etc/bashrc).

如果这给您带来麻烦，我认为使用 unset PROMPT_COMMAND 取消定义该函数是安全的(该函数保留了定义，但未使用).

If this is causing you trouble, I think it's safe to undefine the function with unset PROMPT_COMMAND (that leaves the function defined, but it is not used).

BTW， BASH_REMATCH 最终被设置为"w"，因为该功能逐个字符地遍历您的工作目录，并对它们进行URL编码."w"显然是您工作目录中的最后一个字符.

BTW, BASH_REMATCH wound up being set to "w" because the function steps through your working directory character by character, URL-encoding them as it goes. "w" is apparently the last character in your working directory.

查看该函数，它实际上对提示没有任何作用；它设置终端"窗口标题栏中的文件夹部分.如果您取消设置PROMPT_COMMAND，它将停止更新窗口标题.

looking at the function, it doesn't actually do anything with the prompt; it sets the folder section of the Terminal window title bar. If you unset PROMPT_COMMAND, it'll stop updating the window title.

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