Shell编程之正则表达式（二）

发布时间：2020-07-31 21:14:25 作者：SiceLc
来源：网络阅读：3498

文本处理器

在 Linux/UNIX 系统中包含很多种文本处理器或文本编辑器,其中包括我们之前学习过的VIM 编辑器与 grep 等。而 grep、sed、awk 更是 shell 编程中经常用到的文本处理工具，被称之为 Shell 编程三剑客。

sed 工具

sed（Stream EDitor）是一个强大而简单的文本解析转换工具，可以读取文本，并根据指定的条件对文本内容进行编辑（删除、替换、添加、移动等），最后输出所有行或者仅输出处理的某些行。sed 也可以在无交互的情况下实现相复杂的文本处理操作，被广泛应用于 Shell脚本中，用以完成各种自动化处理任务。

sed 的工作流程主要包括读取、执行和显示三个过程
- 读取：sed 从输入流（文件、管道、标准输入）中读取一行内容并存储到临时的缓冲区中（又称模式空间，pattern space）
- 执行：默认情况下，所有的 sed 命令都在模式空间中顺序地执行，除非指定了行的地址，否则 sed命令将会在所有的行上依次执行
- 显示：发送修改后的内容到输出流。再发送数据后，模式空间将会被清空
- 在所有的文件内容都被处理完成之前，上述过程将重复执行，直至所有内容被处理完
默认情况下,所有的 sed 命令都是在模式空间内执行的，因此输入的文件并不会发生任何变化，除非是用重定向存储输出

sed 命令常见用法

sed 命令有两种格式：

sed [选项] '操作' 参数        //“参数”是指操作的目标文件，当存在多个操作对象时用，文件之间用逗号“，”分隔
或
sed [选项] -f scriptfile 参数   // scriptfile 表示脚本文件，需要用“-f”选项指定

常见sed命令选项
- -e 或--expression=：表示用指定命令或者脚本来处理输入的文本文件
- -f 或--file=：表示用指定的脚本文件来处理输入的文本文件
- -h 或--help：显示帮助
- -n、--quiet 或silent：表示仅显示处理后的结果
- -i：直接编辑文本文件
“操作”用于指定对文件操作的动作行为，也就是sed 的命令。通常情况下是采用的“[n1[,n2]]”操作参数的格式。n1、n2 是可选的，不一定会存在，代表选择进行操作的行数，如操作需要在 5～20 行之间进行，则表示为“5，20 动作行为”。常见的操作包括以下几种
- a：增加，在当前行下面增加一行指定内容
- c：替换，将选定行替换为指定内容
- d：删除，删除选定的行
- i：插入，在选定行上面插入一行指定内容
- p：打印，如果同时指定行，表示打印指定行；如果不指定行，则表示打印所有内容；如果有非打印字符，则以 ASCII 码输出。其通常与“-n”选项一起使用
- s：替换，替换指定字符
- y：字符转换

示例

1）输出符合条件的文本（p 表示正常输出）

[root@localhost opt]# sed -n 'p' httpd.txt     //输出文件所有内容，等同 cat httpd.txt
#
# This is the main Apache HTTP server configuration file.  It contains the
# configuration directives that give the server its instructions.
# See <URL:http://httpd.apache.org/docs/2.4/> for detailed information.
# In particular, see 
# <URL:http://httpd.apache.org/docs/2.4/mod/directives.html>
# for a discussion of each configuration directive.
#
# Do NOT simply read the instructions in here without understanding
# what they do.  They're here only as hints or reminders.  If you are unsure
# consult the online docs. You have been warned.  
#
# Configuration and logfile names: If the filenames you specify for many
# of the server's control files begin with "/" (or "drive:/" for Win32), the
# server will use that explicit path.  If the filenames do *not* begin
# with "/", the value of ServerRoot is prepended -- so 'log/access_log'
# with ServerRoot set to '/www' will be interpreted by the
# server as '/www/log/access_log', where as '/log/access_log' will be
...//省略部分内容....

[root@localhost opt]# sed -n '3p' httpd.txt     //输出第3行内容
# configuration directives that give the server its instructions.

[root@localhost opt]# sed -n '3,5p' httpd.txt    //输出3~5行内容
# configuration directives that give the server its instructions.
# See <URL:http://httpd.apache.org/docs/2.4/> for detailed information.
# In particular, see

[root@localhost opt]# sed -n 'p;n' httpd.txt      //输出所有奇数行内容，n表示读入下一行资料
#
# configuration directives that give the server its instructions.
# In particular, see 
# for a discussion of each configuration directive.
# Do NOT simply read the instructions in here without understanding
# consult the online docs. You have been warned.  
# Configuration and logfile names: If the filenames you specify for many
# server will use that explicit path.  If the filenames do *not* begin
# with ServerRoot set to '/www' will be interpreted by the
# interpreted as '/log/access_log'.
...//省略部分内容....

[root@localhost opt]# sed -n 'n;p' httpd.txt       //输出所有偶数行
# This is the main Apache HTTP server configuration file.  It contains the
# See <URL:http://httpd.apache.org/docs/2.4/> for detailed information.
# <URL:http://httpd.apache.org/docs/2.4/mod/directives.html>
#
# what they do.  They're here only as hints or reminders.  If you are unsure
#
# of the server's control files begin with "/" (or "drive:/" for Win32), the
...//省略部分内容....

[root@localhost opt]# sed -n '1,5{p;n}' httpd.txt    //输出1~5行之间的奇数行（1、3、5行） 
#
# configuration directives that give the server its instructions.
# In particular, see

[root@localhost opt]# sed -n '350,${n;p}' httpd.txt   //输出第350行至文件尾之间的偶数行
#
IncludeOptional conf.d/*.conf
short
wod
woooood
AxyzxyzC
//在执行此命令时，读取的第1行时第350行，读取的第二行是第351行，依次类推，所以输出的偶数行是文件的第351行、第353行直至文件结尾，其中包括空行

sed 命令结合正则表达式时，格式略有不同，正则表达式以“/”包围

[root@localhost opt]# sed -n '/the/p' httpd.txt        //输出包含the的行
# This is the main Apache HTTP server configuration file.  It contains the
# configuration directives that give the server its instructions.
# Do NOT simply read the instructions in here without understanding
# what they do.  They're here only as hints or reminders.  If you are unsure
# consult the online docs. You have been warned.  
# Configuration and logfile names: If the filenames you specify for many
# of the server's control files begin with "/" (or "drive:/" for Win32), the
# server will use that explicit path.  If the filenames do *not* begin
# with "/", the value of ServerRoot is prepended -- so 'log/access_log'
# with ServerRoot set to '/www' will be interpreted by the

[root@localhost opt]# sed -n '4,/the/p' httpd.txt     //输出从第4行至第一个包含the的行
# See <URL:http://httpd.apache.org/docs/2.4/> for detailed information.
# In particular, see 
# <URL:http://httpd.apache.org/docs/2.4/mod/directives.html>
# for a discussion of each configuration directive.
#
# Do NOT simply read the instructions in here without understanding

[root@localhost opt]# sed -n '/the/=' httpd.txt     //输出包含the的所在行的行号，等号（=）用来输出行号
2
3
9
10
11
13
14
...//省略部分内容...

[root@localhost opt]# sed -n '/^sh/p' httpd.txt    //输出以sh开头的行
shirt
short

[root@localhost opt]# sed -n '/[0-9]$/p' httpd.txt     //输出以数字结尾的行
#Listen 12.34.56.78:80
Listen 80
#ServerName www.example.com:80
AddDefaultCharset UTF-8

[root@localhost opt]# sed -n '/\<wood\>/p' httpd.txt      //输出包含的单词wood的行，\<\>代表单词边界
wood

2）删除符合条件的文本（d）

下面命令中 nl 命令用于计算文件的行数，结合该命令可以更加直观地查看到命令执行的结果。

[root@localhost opt]# nl httpd.txt | sed '3d'      //删除第3行
     1  u
     2  # This is the main Apache HTTP server configuration file.  It contains the
     4  # See <URL:http://httpd.apache.org/docs/2.4/> for detailed information.
     5  # In particular, see 
     6  # <URL:http://httpd.apache.org/docs/2.4/mod/directives.html>
     7  # for a discussion of each configuration directive.
...//省略部分内容...

[root@localhost opt]# nl httpd.txt | sed '3,5d'     //删除3~5行
     1  u
     2  # This is the main Apache HTTP server configuration file.  It contains the
     6  # <URL:http://httpd.apache.org/docs/2.4/mod/directives.html>
     7  # for a discussion of each configuration directive.
     ...//省略部分内容...

[root@localhost opt]# nl httpd.txt | sed '/wood/d'     //删除包含wood的行，原第321行被删除
     1  u                                     //删除不包含cross 的行,用!符号表示取反操作,如'/cross/！d'
     2  # This is the main Apache HTTP server configuration file.  It contains the
     3  # configuration directives that give the server its instructions.
     ...//省略部分内容...
   318  short
   319  wd
   320  wod
   322  woooood
   323  AxyzC
   324  AxyzxyzC

[root@localhost opt]# sed '/^[a-z]/d' httpd.txt     //删除以小写字母开头的行
# This is the main Apache HTTP server configuration file.  It contains the
# configuration directives that give the server its instructions.
...//省略部分内容...
# Load config files in the "/etc/httpd/conf.d" directory, if any.
IncludeOptional conf.d/*.conf
AxyzC
AxyzxyzC

[root@localhost opt]# sed '/\.$/d' httpd.txt    //删除以“.”结尾的行
u
# This is the main Apache HTTP server configuration file.  It contains the
# In particular, see 
# <URL:http://httpd.apache.org/docs/2.4/mod/directives.html>
...//省略部分内容...

[root@localhost opt]# sed '/^$/d' httpd.txt      //删除所有空行
u
# This is the main Apache HTTP server configuration file.  It contains the
# configuration directives that give the server its instructions.
# See <URL:http://httpd.apache.org/docs/2.4/> for detailed information.
# In particular, see 
# <URL:http://httpd.apache.org/docs/2.4/mod/directives.html>
# for a discussion of each configuration directive.
//注意： 若是删除重复的空行，即连续的空行只保留一个， 执行“ sed –e ‘/^$/{n;/^$/d}’ httpd.txt”命令即可实现。其效果与“cat -s test.txt”相同，n 表示读下一行数据。

3）替换符合条件的文本

在使用 sed 命令进行替换操作时需要用到 s（字符串替换）、c（整行/整块替换）、y（字符转换）命令选项

[root@localhost opt]# sed 's/the/THE/' httpd.txt     //将每行中第一个the替换为THE
u
# This is THE main Apache HTTP server configuration file.  It contains the
# configuration directives that give THE server its instructions.
# See <URL:http://httpd.apache.org/docs/2.4/> for detailed information.
# In particular, see 
...//省略部分内容...

[root@localhost opt]# vim aaa.txt       //编辑一个新文件
llllll
llllll
llllll                                  //编辑内容
llllll
llllll
llllll
~                                                                             
~                                                                             
:wq                                     //保存退出
[root@localhost opt]# sed 's/l/L/3' aaa.txt     //将每行中第3个l替换为L
llLlll
llLlll                                           //显示替换后内容
llLlll
llLlll
llLlll
llLlll

[root@localhost opt]# sed 's/the/THE/g' httpd.txt    //将文件中多有的the替换为THE
u
# This is THE main Apache HTTP server configuration file.  It contains THE
# configuration directives that give THE server its instructions.
# See <URL:http://httpd.apache.org/docs/2.4/> for detailed information.
# In particular, see 
...//省略部分内容...

[root@localhost opt]# sed 's/o//g' httpd.txt      //将文件中所有的o删除（替换为空串）
u
# This is the main Apache HTTP server cnfiguratin file.  It cntains the
# cnfiguratin directives that give the server its instructins.
...//省略部分内容...
shirt
shrt
wd
wd
wd
wd
AxyzC
AxyzxyzC

[root@localhost opt]# sed 's/^/#/' aaa.txt     //在每行行首插入#号
#llllll
#llllll
#llllll
#llllll
#llllll
#llllll

[root@localhost opt]# sed 's/$/eof/' aaa.txt     //在每行行尾插入字符串eof
lllllleof
lllllleof
lllllleof
lllllleof
lllllleof
lllllleof

[root@localhost opt]# vim aaa.txt        //编辑文件
llllll
llllll
llllll
llllll
llllll
llllll
aaaaaa
aaaaaa                        //添加内容
aaaaaa
aaaaaa
aaaaaa
~                                                                             
~                                                                             
:wq                            //保存退出
[root@localhost opt]# sed '/a/s/^/#/' aaa.txt         //在包含 a 的每行行首插入#号
llllll
llllll
llllll
llllll
llllll
llllll
#aaaaaa
#aaaaaa
#aaaaaa
#aaaaaa
#aaaaaa

[root@localhost opt]# sed '3,5s/l/L/g' aaa.txt    //将第 3~5 行中的所有 l 替换为 L
llllll
llllll
LLLLLL
LLLLLL
LLLLLL
llllll
aaaaaa
aaaaaa
aaaaaa
aaaaaa
aaaaaa

[root@localhost opt]# vim bbb.txt    //编辑一个新文件
this is
the wood
wood
wod                             //编辑内容
the wood
this is test
~                                                                             
~                                                                             
:wq                               //保存退出
[root@localhost opt]# sed '/the/s/o/O/g' bbb.txt    //将包含 the 的所有行中的 o 都替换为 O
this is
the wOOd
wood
wod
the wOOd
this is test

4）迁移符合条件的文本

H，复制到剪贴板；g、G，将剪贴板中的数据覆盖/追加至指定行；w，保存为文件；r，读取指定文件；a，追加指定内容。

[root@localhost opt]# sed '/the/{H;d};$G' bbb.txt    //将包含the 的行迁移至文件末尾,{;}用于多个操作
this is
wood
wod
this is test

the wood
the wood

[root@localhost opt]# sed '1,3{H;d};8G' aaa.txt     //将1~3行内容迁移到8行之后
llllll
llllll
llllll
aaaaaa
aaaaaa

llllll
llllll
llllll
aaaaaa
aaaaaa
aaaaaa

[root@localhost opt]# sed '/the/w ccc.txt' bbb.txt     //将包含the 的行另存为文件ccc.txt
this is
the wood
wood
wod
the wood
this is test
[root@localhost opt]# cat ccc.txt                  //查看保存的文件内容
the wood
the wood

[root@localhost opt]# sed '/the/r /etc/hostname' bbb.txt   
this is                                  //将文件/etc/hostname 的内容添加到包含the 的每行以后
the wood
localhost.localdomain
wood
wod
the wood
localhost.localdomain
this is test

[root@localhost opt]# sed '3aNEW' bbb.txt   //在第 3 行后插入一个新行,内容为 NEW
this is
the wood
wood
NEW
wod
the wood
this is test

[root@localhost opt]# sed '/the/aNEW' bbb.txt     //在包含the 的每行后插入一个新行,内容为 NEW
this is
the wood
NEW
wood
wod
the wood
NEW
this is test

[root@localhost opt]# sed '3aNEW\nNEW2' bbb.txt  //在第 3 行后插入多行内容,中间的\n 表示换行
this is
the wood
wood
NEW
NEW2
wod
the wood
this is test

5）使用脚本编辑文件

使用 sed 脚本，将多个编辑指令存放到文件中（每行一条编辑指令），通过“-f”选项来调用。

sed '1,3{H;d};6G' bbb.txt    //将1~3行的内容迁移到6行之后

[root@localhost opt]# vim test
1,3H
1,3d
6G
~                                                                            
:wq 
[root@localhost opt]# sed -f test bbb.txt 
wod
the wood
this is test

this is
the wood
wood

6） sed 直接操作文件示例

编写一个脚本，用来调整 vsftpd 服务配置：禁止匿名用户，但允许本地用户（也允许写入）。

[root@localhost ~]# **vim local_only_ftp.sh** 
#!/bin/bash
#指定样本文件路径、配置文件路径
SAMPLE="/usr/share/doc/vsftpd-3.0.2/EXAMPLE/INTERNET_SITE/vsftpd.conf " CONFIG="/etc/vsftpd/vsftpd.conf"
#备份原来的配置文件,检测文件名为/etc/vsftpd/vsftpd.conf.bak 备份文件是否存在, 若不存在则使用 cp 命令进行文件备份
[ ! -e "$CONFIG.bak" ] && cp $CONFIG $CONFIG.bak      //基于样本配置进行调整,覆盖现有文件
sed -e '/^anonymous_enable/s/YES/NO/g' $SAMPLE > $CONFIG
sed -i -e '/^local_enable/s/NO/YES/g' -e '/^write_enable/s/NO/YES/g' $CONFIG grep "listen" $CONFIG || sed -i '$alisten=YES' $CONFIG
# 启动vsftpd 服务,并设为开机后自动运行systemctl restart vsftpd
systemctl enable vsftpd
[root@localhost ~]# **chmod +x local_only_ftp.sh

Shell编程之正则表达式（二）

文本处理器

sed 工具

sed 命令常见用法

示例

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