zsh - Zsh - 什么是 $~variable 扩展，它与 $~==variable 有什么不同？

Question

我从Zsh 邮件列表中找到了这个 sudo 包装器：

alias sudo='noglob do_sudo '
function do_sudo
{
    integer glob=1
    local -a run
    run=( command sudo )
    if [[ $# -gt 1 && $1 = -u ]]; then
        run+=($1 $2)
        shift ; shift
    fi
    (($# == 0)) && 1=/bin/zsh
    while (($#)); do
        case "$1" in
        command|exec|-) shift; break ;;
        nocorrect) shift ;;
        noglob) glob=0; shift ;;
        *) break ;;
        esac
    done
    if ((glob)); then
        PATH="/sbin:/usr/sbin:/usr/local/sbin:$PATH" $run $~==*
    else
        PATH="/sbin:/usr/sbin:/usr/local/sbin:$PATH" $run $==*
    fi
}

它用于$~==*扩展文件模式。这种扩展叫什么？它记录在哪里？（真的不知道如何搜索这个，'美元波浪号扩展'，'文件名扩展'，'波浪号扩展'都给了我一些不相关的结果......）

我注意到这实际上$~var也有效，例如

$ touch foo bar
$ t1='fo*'
$ echo $~t1
foo
$ t2=('fo*' 'ba*')
$ echo $~t2
foo bar

和 有什么不同$~==t1吗？顺便说一句，变量名和变量名之间似乎可以有任意数量的=s ，看起来都一样。$$~=t1 $=~t1 $~=====t1

标签： zsh

Answer 1

感谢@chepner 的提示。这是我在zshexpn手册中找到的：

${=spec}
      Perform  word  splitting  using  the rules for SH_WORD_SPLIT during the evaluation of spec, but regardless of whether the parameter appears in double quotes; if the `=' is
      doubled, turn it off.  This forces parameter expansions to be split into separate words before substitution, using IFS as a delimiter.  This is done  by  default  in  most
      other shells.

      Note that splitting is applied to word in the assignment forms of spec before the assignment to name is performed.  This affects the result of array assignments with the A
      flag.

${~spec}
      Turn on the GLOB_SUBST option for the evaluation of spec; if the `~' is doubled, turn it off.  When this option is set, the string resulting from the expansion will be in‐
      terpreted  as  a pattern anywhere that is possible, such as in filename expansion and filename generation and pattern-matching contexts like the right hand side of the `='
      and `!=' operators in conditions.

      In nested substitutions, note that the effect of the ~ applies to the result of the current level of substitution.  A surrounding pattern operation on the result may  can‐
      cel  it.   Hence,  for  example,  if  the  parameter  foo is set to *, ${~foo//\*/*.c} is substituted by the pattern *.c, which may be expanded by filename generation, but
      ${${~foo}//\*/*.c} substitutes to the string *.c, which will not be further expanded.

因此，~启用将模式（规范）替换为文件名的 globbing。==确保对引号中的字符串禁用分词。

例如：

$ touch foo bar
$ spec='fo* ba*'
$ echo $~spec
zsh: no matches found: fo* ba*
$ echo $~=spec
foo bar
$ echo $~==spec
zsh: no matches found: fo* ba*
$ function test1() { printf '1=%s 2=%s\n' $1 $2; }
$ test1 $spec
1=fo* ba* 2=
$ test1 $~spec
zsh: no matches found: fo* ba*
$ test1 $~=spec
1=foo 2=bar
$ test1 $~==spec
zsh: no matches found: fo* ba*
$ test1 $=spec
1=fo* 2=ba*