在egrep的例行前pression管道bash的输入参数 [英] piping bash input arguments in egrep's regular expression

问题描述

下面是我试图运行脚本

#!/bin/bash

charlist=$1 #possible input:cat
wordlength=$2 #possible input: 3

cat ./nounlist | egrep \b[${charlist}]\b{${wordlength}}

输出：无​​＃应该抓到以下（使用命令行）

output: nothing.# should've caught the following(using command line)

$ cat nounlist | egrep "\b[cat]{3}\b"
act
cat's_cradle
cat
cat-o'-nine-tails
cat's-paw
Sno-cat
act
act
act
act
rat-a-tat-tat
cat
cat's-claw
cat's_foot
cat's-ear
cat's-tail
cat's-ear
cat's_eye

基本上我试图写一个脚本，需要两个参数（词库，字长），并在获取，在词表包括焦炭和具有可变字长的长度nounlist所有单词。我想知道的是如何把bash的变量的egrep的常规前pression为字符串？

basically I am trying to write a script that takes two arguments(wordlist, wordlength) and fetch all the words in the nounlist that consist of the char in the wordlist and has the length of wordlength variable. What I want to know is how to put bash variables in egrep's regular expression as strings?

谢谢！

推荐答案

您需要包装的说法在双引号，这样的Bash不会尝试处理反斜杠，并且移动第二 \\ b 来的之后的的 {$ {}字长} ：

You need to wrap the argument in double-quotes so that Bash doesn't try to handle the backslashes, and move the second \b to after the {${wordlength}}:

cat ./nounlist | egrep "\b[${charlist}]{${wordlength}}\b"

（如果你运行回声\\ b ，你会看到，它只是打印 B ，这是因为巴什假定 \\ 是那里prevent b 的有什么特殊的意义，所以它删除。 ）

(If you run echo \b, you'll see that it just prints b. This is because Bash assumes that the \ is there to prevent b from having any special meaning; so it removes it.)

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