Question

我找到了如下语法。

${VARIABLE##*/}

##*/的含义是什么？

我知道*/中ls */的含义，但不知道上面的语法是什么。

Answer 1

来自man bash：

   ${parameter#word}
   ${parameter##word}
          Remove matching prefix pattern.  The word is expanded to produce
          a pattern just as in pathname expansion.  If the pattern matches
          the beginning of the value of parameter, then the result of  the
          expansion  is  the expanded value of parameter with the shortest
          matching pattern (the ``#'' case) or the longest  matching  pat‐
          tern  (the  ``##''  case)  deleted.  If parameter is @ or *, the
          pattern removal operation is applied to each positional  parame‐
          ter in turn, and the expansion is the resultant list.  If param‐
          eter is an array variable subscripted with @ or *,  the  pattern
          removal  operation  is  applied  to  each member of the array in
          turn, and the expansion is the resultant list.

Answer 2

这个例子将说清楚：

VARIABLE='abcd/def/123'

echo "${VARIABLE#*/}"
def/123

echo "${VARIABLE##*/}"
123

##*/正在从输入开始中删除 /的最长匹配。

#*/正在从输入开始中删除 /之后的最短匹配。

PS：在Unix shell中使用所有大写变量名称并不是很好的做法。最好使用variable代替VARIABLE。

unix中## * /的含义是什么？

2 个答案: