zsh:检查字符串是否在数组中

Question

例如

foo=(a b c)

现在,我该怎么做一个简单的检查,如果b是$foo？

Answer 1

您可以使用反向订阅:

pax$ foo=(a b c)

pax$ if [[ ${foo[(r)b]} == b ]] ; then ; echo yes ; else ; echo no ; fi
yes

pax$ if [[ ${foo[(r)x]} == x ]] ; then ; echo yes ; else ; echo no ; fi
no

你会发现man zshparam下面的数据Subscript Flags(至少在zsh 4.3.10下面Ubuntu 10.10).

或者(感谢geekosaur),您可以使用:

pax$ if [[ ${foo[(i)b]} -le ${#foo} ]] ; then ; echo yes ; else ; echo no ; fi

您只需执行以下操作即可看到从这两个表达式中获得的内容:

pax$ echo ${foo[(i)a]} ${#foo}
1 3

pax$ echo ${foo[(i)b]} ${#foo}
2 3

pax$ echo ${foo[(i)c]} ${#foo}
3 3

pax$ echo ${foo[(i)d]} ${#foo}
4 3

Answer 2

(( ${foo[(I)b]} )) \
  && echo "it's in" \
  || echo "it's somewhere else maybe"

Answer 3

如果找到匹配项，反向下标将始终返回某些内容，如果找不到匹配项，则不返回任何内容。我们可以使用它来进一步简化答案。

$ foo=(a b c)

$ [[ -n "${foo[(r)b]}" ]] && echo 'b was found.' || echo 'b was not found.'
b was found.

$ [[ -n "${foo[(r)d]}" ]] && echo 'd was found.' || echo 'd was not found.'
d was not found.