用于这种bash文件名提取技术？
我有一个bash脚本的一部分，它获得了一个没有扩展名的文件名，但我试图理解这里发生了什么。 什么是“%%”？ 有人可以详细说明bash在后台做什么吗？ 这种技术如何在一般基础上使用？
#!/bin/bash
for src in *.tif
do
txt=${src%%.*}
tesseract ${src} ${txt}
done
它取消了文件扩展名（这里是： .tif ），示例：
$ for A in test.py test.sh test.xml test.xsl; do echo "$A: ${A%%.*}"; done
test.py: test
test.sh: test
test.xml: test
test.xsl: test
来自bash手册：
${parameter%%word}
The word is expanded to produce a pattern just as in pathname expansion. If the
pattern matches a trailing portion of the expanded 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 pattern (the ``%%''
case) deleted. If parameter is @ or *, the pattern removal operation is applied
to each positional parameter in turn, and the expansion is the resultant list.
If parameter 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.
这里是bash手册页的输出
${parameter%%word}
The word is expanded to produce a pattern just as in pathname
expansion. If the pattern matches a trailing portion of the
expanded value of parameter, then the result of the expansion is
the expanded value of parameter with the shortest matching pat-
tern (the ``%'' case) or the longest matching pattern (the
``%%'' case) deleted. If parameter is @ or *, the pattern
removal operation is applied to each positional parameter in
turn, and the expansion is the resultant list. If parameter 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.
显然bash有几个“ 参数扩展 ”工具，其中包括：
只需替换值...
${parameter}
扩展为子字符串...
${parameter:offset}
${parameter:offset:length}
替换参数值的长度...
${#parameter}
在参数开始时进行扩展...
${parameter#word}
${parameter##word}
在参数结尾处扩展匹配...
${parameter%word}
${parameter%%word}
扩展参数以查找和替换字符串...
${parameter/pattern/string}
这些是我对我认为从手册页的这一部分理解的部分的解释。 如果我错过了重要的事情，请告诉我。
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