zsh中的局部变量：zsh中bash的“export -n”相当于什么

Question

我试图在 zsh 中将变量的范围包含在 shell 中，并且没有孩子看到它。例如，我在 .zshrc 中输入：

GREP_OPTIONS=--color=always

但是，如果我使用以下内容运行 shell 脚本：

#!/bin/bash
echo $GREP_OPTIONS

输出是：

--color=always

虽然我希望它为空（上面的 shell 脚本根本不应该看到 GREP_OPTIONS 变量）。

在 bash 中，可以说: export -n GREP_OPTIONS=--color=always，这将防止这种情况发生。我如何在 zsh 中完成此操作？

Answer 1

export在 zsh 中是 的简写typeset -gx，其中属性g表示“全局”（与函数的局部相反），属性x表示“导出”（即在环境中）。因此：

typeset +x GREP_OPTIONS

这也适用于 ksh 和 bash。

如果您一开始从不导出GREP_OPTIONS，则无需取消导出。

您还可以使用间接的、可移植的方式：取消设置变量将其取消导出。在 ksh/bash/zsh 中，如果变量是只读的，这将不起作用。

tmp=$GREP_OPTIONS
unset GREP_OPTIONS
GREP_OPTIONS=$tmp

Answer 2

您可以使用匿名函数为变量提供范围。来自man zshall：

ANONYMOUS FUNCTIONS
       If no name is given for a function, it is `anonymous'  and  is  handled
       specially.  Either form of function definition may be used: a `()' with
       no preceding name, or a `function' with an immediately  following  open
       brace.  The function is executed immediately at the point of definition
       and is not stored  for  future  use.   The  function  name  is  set  to
       `(anon)'.

       Arguments to the function may be specified as words following the clos?
       ing brace defining the function, hence if there are none  no  arguments
       (other than $0) are set.  This is a difference from the way other func?
       tions are parsed: normal function definitions may be followed  by  cer?
       tain  keywords  such  as `else' or `fi', which will be treated as argu?
       ments to anonymous functions, so that a newline or semicolon is  needed
       to force keyword interpretation.

       Note also that the argument list of any enclosing script or function is
       hidden (as would be the case for any  other  function  called  at  this
       point).

       Redirections  may be applied to the anonymous function in the same man?
       ner as to a current-shell structure enclosed in braces.  The  main  use
       of anonymous functions is to provide a scope for local variables.  This
       is particularly convenient in start-up files as these  do  not  provide
       their own local variable scope.

       For example,

              variable=outside
              function {
                local variable=inside
                print "I am $variable with arguments $*"
              } this and that
              print "I am $variable"

       outputs the following:

              I am inside with arguments this and that
              I am outside

       Note  that  function definitions with arguments that expand to nothing,
       for example `name=; function $name { ... }', are not treated as  anony?
       mous  functions.   Instead, they are treated as normal function defini?
       tions where the definition is silently discarded.

但除此之外 - 如果您根本不使用exportin 您.zshrc的变量，则该变量应该只在您当前的交互式会话中可见，并且不应导出到子 shell。

正如 terdon 在他的评论中解释的那样：export -ninbash只会导致从变量中删除“export”属性，因此使用export -n GREP_OPTIONS=--color=always等同于根本不使用 export - GREP_OPTIONS=--color=always。

换句话说，要获得所需的行为，请不要使用export. 相反，在你的.zshrc，你应该有

GREP_OPTIONS=--color=always

这将使该变量可用于您运行的所有（交互式、非登录）shell，就像您希望的那样，但它不会导出到子 shell。