以各种方式被引用时，如何正确地转义bash变量 [英] How can I properly escape bash variables when being quoted in various ways

问题描述

我有以下代码：

set -o xtrace
openDirectory ()
{
    lxterminal --command="zsh -c 'cd "$1"; zsh -i' "
}

# Handle argument.
if [ "$@" ]
then
  openDirectory ~/Projects/Clients/"@1"
  cd $1
fi

如果传递的参数中有空格，此操作将失败。

This fails if there is a space in the argument passed.

lxterminal '--command=zsh -c '\''cd /home/chris/Projects/Clients/Test' - 'Space; zsh -i'\'' '
cd Test - Space
cd: too many arguments

如何正确地避免这种情况？

How can I properly escape this? Is this even feasible to be done with something like bash?

推荐答案

假设封闭的外壳确实是bash（因为这个问题已被标记），这甚至可行吗？ ），则可以使用 printf -v varname％q $ var 存储值 var 放入名为 varname 的变量中，例如：

Assuming the enclosing shell really is bash (as the question is tagged), you can use printf -v varname %q "$var" to store a safely quoted instance of the value of var into the variable named varname, as such:

openDirectory()
{
    local cd_cmd cmd
    printf -v cd_cmd '%q ' cd "$1"
    printf -v cmd '%q ' zsh -c "$cd_cmd && zsh -i"
    lxterminal --command="$cmd"
}

printf'％q'计算为给定字符串的版本，当bash eval 'ed时，该版本（或具有等效语义的任何外壳程序），求值为原始文字值。

printf '%q' evaluates to a version of the given string which will, when eval'ed by bash (or any shell with equivalent semantics), evaluate to the original literal value.

要解释为什么这样做是这样的：

To explain why this is done that way:

• 在上面，代码本身包含的所有引号字符都是句法而不是文字：取决于 all 引用和转义的 printf％q 。这是一种最佳实践方法：使用文字引号意味着生成的数据中的文字可以转义这些引号。


• 运行shell指令，例如& & 通过外壳引号会将它们转换为文字数据。因此，当我们将&& 作为参数传递给<$ c $时，我们希望是文字数据，而不是语法c> -c ，但不是由远程Shell处理时的文字数据，这就是为什么它仅出现在 last 引用传递中的原因。

• In the above, all quote characters included in the code itself are syntactic rather than literal: We're depending on printf %q for all quoting and escaping. This is a best-practice approach: Using literal quotes means that literals inside the data being generated are able to escape those quotes.
• Running shell directives such as && through shell quoting will make them into literal data. Thus, we want the && to be literal data rather than syntax when we're passing it as an argument to -c, but not literal data when handled by the remote shell -- this is why it's only present in the last quoting pass.

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