为什么＆＃x27;＆＃x27; grep [ff] irst *.txt＆＃x27;＆＃x27;不匹配包含“首先”的文件？

发布于 2025-01-27 15:13:12 字数 552 浏览 4 评论 0原文

孟德尔·库珀（Mendel Cooper）的“高级bash施法指南”中的示例...

$bash --version | head -1
GNU bash, version 5.0.17(1)-release (x86_64-pc-linux-gnu)
$mkdir Quoting_Experimenting
$cd Quoting_Experimenting
$echo This is the first line of file1.txt > file1.txt
$echo This is the First line of file2.txt > file2.txt
$grep [fF]irst *.txt
file1.txt:This is the first line of file1.txt
file2.txt:This is the First line of file2.txt
$touch first
$grep [fF]irst *.txt
file1.txt:This is the first line of file1.txt

为什么GREP首次创建后找不到file2.txt？

原文

Example from Mendel Cooper's "Advanced Bash-Scripting Guide"...

$bash --version | head -1
GNU bash, version 5.0.17(1)-release (x86_64-pc-linux-gnu)
$mkdir Quoting_Experimenting
$cd Quoting_Experimenting
$echo This is the first line of file1.txt > file1.txt
$echo This is the First line of file2.txt > file2.txt
$grep [fF]irst *.txt
file1.txt:This is the first line of file1.txt
file2.txt:This is the First line of file2.txt
$touch first
$grep [fF]irst *.txt
file1.txt:This is the first line of file1.txt

Why does grep not find file2.txt after first has been created?

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小忆控 2025-02-03 15:13:12

您需要在grep命令中引用搜索模式，否则shell扩展了未引用的模式 [ff] irst to holly first仅（由于文件名首先存在于当前目录中）：

请使用：

grep '[fF]irst' *.txt

- 根据该文档的官方狂欢文件

（重点是我的）：

单词拆分后，除非设置了-f选项（请参阅set indendin），请bash扫描每个单词的字符'*'*'，'？'，<代码>'['。如果这些字符之一出现，并且是未引用，则该单词被视为模式，并用字母排序的文件名匹配图案。

You need to quote the search pattern in grep command otherwise shell expands unquoted pattern [fF]irst to first only (due to filename first being present in your current directory):

So use:

grep '[fF]irst' *.txt

- Official BASH documentation on filename expansion

As per this doc (emphasis is mine):

After word splitting, unless the -f option has been set (see The Set Builtin), Bash scans each word for the characters ‘*’, ‘?’, and ‘[’. If one of these characters appears, and is not quoted, then the word is regarded as a pattern, and replaced with an alphabetically sorted list of filenames matching the pattern.

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