1、IP地址的正则表达式： [0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}

2、grep用法

//在多级目录中对文本进行递归检索

[root@localhost program_test]# grep "yang" ./ -Rn

./test.txt:6:laoyang

./right.txt:1:1 yang man

//忽略大小写匹配

[root@localhost program_test]# echo hello world | grep -i "HELLO"

hello world

//递归搜索所有.c和.cpp文件

[root@localhost program_test]# grep "main()" . -r --include *.{c,cpp}

./hello.c:int main()
sin.c:int main()
hello.cpp:int main()

 

//匹配某个结果之后的几行

[root@localhost program_test]# echo -e "a\nb\nc\na\nb\nc"| grep a -A 1

a
b
--
a
b

 

3、cut命令

cut,将文本按照列进行切割的小工具。

//-d分界符; -f要提取的列

[root@localhost program_test]# cut -d ":" -f5 --complement passwd_yang

root:x:0:0:/root:/bin/bash
bin:x:1:1:/bin:/sbin/nologin

 

[root@localhost program_test]# cut -c1-5 passwd_yang 

root:
bin:x
daemo
adm:x

 

//统计特定文件中的词频

[root@localhost program_test]# cat word_freq.sh

#!/bin/bash

 

if [ $# -ne 1 ];

then

echo "Usage: $0 filename"

exit -1

fi

 

filename=$1

 

egrep -o "\b[[:alpha:]]+\b" $filename | \

awk '{ count[$0]++ } \

END { printf("%-14s%s\n","word","Count");\

for(ind in count) \

{ printf("%-14s%d\n",ind,count[ind]); } }'

4、sed命令（stream editor 流编辑器)

适用文本处理.

//1.替换,从第3个开始替换

[root@localhost program_test]# echo this thisthisthis | sed 's/this/THIS/3g'

this thisTHISTHIS

//2.删掉空白行

[root@localhost program_test]# sed '/^$/d' choice.sh

 

//3.已匹配的字符串标记&

[root@localhost program_test]# echo this is an example | sed 's/\w\+/[&]/g'

[this] [is] [an] [example]

 

//4.替换举例.

[root@localhost program_test]# cat sed_data.txt 

11 abc 111 this 9 file contains 111 11 88 numbers 0000
[root@localhost program_test]# cat sed_data.txt | sed 's/\b[0-9]\{3\}\b/NUMBER3/g'
11 abc NUMBER3 this 9 file contains NUMBER3 11 88 numbers 0000