使用此bash的文件名萃取技术？ [英] Uses for this bash filename extraction technique?

问题描述

我有一个是得到一个文件名没有扩展名bash脚本的一部分，但我想知道究竟怎么回事就在这里。什么是%%的呢？谁能细说什么bash的是做幕后？如何解决这个技术来一般的基础上使用？

 ＃！/斌/庆典在* .TIF SRC
    做
    TXT = $ {SRC %%。*}
    的tesseract $ {SRC} $ {} TXT
    DONE
 

解决方案

它摆脱了文件的扩展名（这里的的.tif ） ，样本：

  $对于A在test.py test.sh的test.xml test.xsl;做回声$ A：$ {A %%。*}; DONE
test.py：测试
test.sh：测试
的test.xml：测试
test.xsl：测试
 

从bash的手册：

  $ {参数%%词}
          word被扩展为一个模式，就像路径扩展。如果
          模式参数扩展后的值的尾部相匹配，那么，
          扩张的结果是参数的最短扩展值
          匹配（``％''的情况）或者最长的匹配（``%%''
          情况）删除。如果参数是@或*，模式删除应用
          要依次在每个位置参数，最后扩展为结果的列表。
          如果参数是@或*，模式删除下标数组变量
          操作应用于反过来阵列的每个成员，并且膨胀是
          结果的列表。
 

I have a portion of a bash script that is getting a filename without extension, but I'm trying to understand what is really going on here. What are the "%%"'s for? Can someone elaborate on what bash is doing behind the scenes? How can this technique be used on a general basis?

#!/bin/bash

for src in *.tif
    do
    txt=${src%%.*}
    tesseract ${src} ${txt}
    done

解决方案

It gets rid of the filename extension (here: .tif), sample:

$ 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

from bash manual:

   ${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.

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