参考书目：鸟哥的LINUX私房菜基础学习篇（第三版）
Linux Shell Scripting Cookbook

本节主要内容

1. 基础正则表达式

1. 基础正则表达式

(1)^行开始符

^匹配一行的开始，例如’^Spark’ 匹配所有Spark开始的行

//grep -n表示查找到的结果显示行号
root@sparkslave02:~/ShellLearning# grep -n '^Spark' /hadoopLearning/spark-1.5.0-bin-hadoop2.4/README.md 
3:Spark is a fast and general cluster computing system for Big Data. It provides
22:Spark is built using [Apache Maven](http://maven.apache.org/).
53:Spark also comes with several sample programs in the `examples` directory.
83:Spark uses the Hadoop core library to talk to HDFS and other Hadoop-supported

(2)$行结束符

匹配一行的结束，例如′Spark’ 匹配所有以Spark结束的行

root@sparkslave02:~/ShellLearning# grep -n 'Spark$' /hadoopLearning/spark-1.5.0-bin-hadoop2.4/README.md 
1:# Apache Spark
20:## Building Spark

(3).匹配任意一个字符

例如 Spa.k可以匹配Spark、Spaak等

root@sparkslave02:~/ShellLearning# grep -n 'Spa.k' /hadoopLearning/spark-1.5.0-bin-hadoop2.4/README.md 
1:# Apache Spark
3:Spark is a fast and general cluster computing system for Big Data. It provides
6:rich set of higher-level tools including Spark SQL for SQL and 
//其它省略

上面没有匹配小写spark，要匹配可以采用

//-i选项表示忽略大小写
root@sparkslave02:~/ShellLearning# grep -in 'Spa.k' /hadoopLearning/spark-1.5.0-bin-hadoop2.4/README.md 

(4)[]匹配其中一个

[Ss]park只匹配Spark和spark

root@sparkslave02:~/ShellLearning# grep -n '[Ss]park' /hadoopLearning/spark-1.5.0-bin-hadoop2.4/README.md 
1:# Apache Spark
3:Spark is a fast and general cluster computing system for Big Data. It provides
6:rich set of higher-level tools including Spark SQL for SQL and DataFrames,
8:and Spark Streaming for stream processing.
10:<http://spark.apache.org/>
//其它省略

(5) [^]不匹配[]中的任何一个字符

例如 ‘[^T]he’ ，不匹配The，但可匹配 the、che等

root@sparkslave02:~/ShellLearning# grep -n '[^T]he' /hadoopLearning/spark-1.5.0-bin-hadoop2.4/README.md 

(6) [-]匹配固定范围的字符

例如[a-h]he，只匹配ahe、bhe、che…hhe，不匹配ihe、the等

root@sparkslave02:~/ShellLearning# grep -n '[a-h]he' /hadoopLearning/spark-1.5.0-bin-hadoop2.4/README.md 
1:# Apache Spark
6:rich set of higher-level tools including Spark SQL for SQL and DataFrames,
10:<http://spark.apache.org/>
16:guide, on the [project web page](http://spark.apache.org/documentation.html)

(7)? 匹配0次或1次

例如t?he只匹配he和the，不匹配tthe

//?属于特殊符号，需要\进行转义
root@sparkslave02:~/ShellLearning# grep -n 't\?he' /hadoopLearning/spark-1.5.0-bin-hadoop2.4/README.md 
1:# Apache Spark
6:rich set of higher-level tools including Spark SQL for SQL and DataFrames,
10:<http://spark.apache.org/>
15:You can find the latest Spark documentation, including a programming
16:guide, on the [project web page](http://spark.apache.org/documentation.html)
//其它省略

(8)+ 至少匹配一次

‘S+park’可以匹配Spark、SSpark、SSSpark等

root@sparkslave02:~/ShellLearning# grep -n 'S\+park' /hadoopLearning/spark-1.5.0-bin-hadoop2.4/README.md 

(9) * 匹配零次或多少

‘S*park’可匹配park、Spark、SSpark、SSSpark等

root@sparkslave02:~/ShellLearning# grep -n 'S*park' /hadoopLearning/spark-1.5.0-bin-hadoop2.4/README.md 
1:# Apache Spark
3:Spark is a fast and general cluster computing system for Big Data. It provides
6:rich set of higher-level tools including Spark SQL for SQL and DataFrames,
8:and Spark Streaming for stream processing.
10:<http://spark.apache.org/>
15:You can find the latest Spark documentation, including a programming
//其它省略

(10) {n}，匹配n次

例如[a-z]{3}，匹配任意3个小写字母，等同于[a-z][a-z][a-z]

root@sparkslave02:~/ShellLearning# grep -n '[a-z]\{3\}' /hadoopLearning/spark-1.5.0-bin-hadoop2.4/README.md 
1:# Apache Spark
3:Spark is a fast and general cluster computing system for Big Data. It provides

(11) 其它限定次数匹配

{n, }至少匹配n次
{n, m}至少匹配n次，最多匹配m次

(13) 转义字符\

Ubuntu Linux ?,+,(,), {,}是特殊字符，在使用正则表达式时，如果不加转义符，会匹配将其视为一般字符，如果要设置为正则表达式式符，需要使用\进行转义，前面的例子已经给出示例。

(14) ()匹配一组字符

例如Sp(ar)\?k 匹配Spark和Spk，

root@sparkslave02:~/ShellLearning# echo "Spark Spk Spak" | grep -n 'Sp\(ar\)\?k'
1:Spark Spk Spak

(15) URL匹配实战

root@sparkslave02:~/ShellLearning/Chapter15# grep -n '[A-Za-z]*://[A-Za-z]*\.\(\([A-Za-z]*\)\.\?\)*' /hadoopLearning/spark-1.5.0-bin-hadoop2.4/README.md 

上面整个例子可以分下列步骤完成：
(1)匹配http://

root@sparkslave02:~/ShellLearning/Chapter15# grep -n '[A-Za-z]*://' /hadoopLearning/spark-1.5.0-bin-hadoop2.4/README.md 

(2)匹配域名

root@sparkslave02:~/ShellLearning/Chapter15# grep -n '[A-Za-z]*://[A-Za-z]*\.[A-Za-z]*' /hadoopLearning/spark-1.5.0-bin-hadoop2.4/README.md

(3)处理重复部分

root@sparkslave02:~/ShellLearning/Chapter15# grep -n '[A-Za-z]*://[A-Za-z]*\.\(\([A-Za-z]*\)\.\?\)*' /hadoopLearning/spark-1.5.0-bin-hadoop2.4/README.md