shell编程之sed命令详解
shell 编程之 sed
sed 编辑器介绍
sed（流编辑器）是一种非交互式文本处理工具，基于预设规则逐行处理数据流（文件或管道输入）。它将当前行存入模式空间，按命令处理后输出到标准输出，不修改原始文件。
工作流程
- 读取一行数据到模式空间；
- 按顺序执行编辑命令；
- 输出处理后的行；
- 重复直至所有行处理完毕。
命令格式
sed [options] 'script' [file1 file2...]
- 选项：
-
选项
描述 -e script显式指定编辑命令（可多条，用分号分隔） -f file从文件读取编辑命令 -n禁止默认输出，需配合 p等命令手动输出,默认就是改了也输出，不改原样输出
| 选项 | 正则表达式类型 | 支持的元字符 | 示例 |
|---|---|---|---|
无 -r | 基本正则表达式 | ^、$、.、*、[]、\( \)、|（需转义） | sed 's/[0-9]*/num/' |
-r | 扩展正则表达式 | 所有基本元字符 + 、?、()、|、{}（无需转义） | sed -r 's/[0-9]+/num/' |
命令执行方式
- 命令行直接定义单条命令
echo "This is a test" | sed 's/test/big test/' # 输出：This is a big test - 命令行定义多条命
1、无-e直接分号分隔
[root@free ~]# sed -e 's/brown/green/; s/dog/cat/' data1.txt
The quick green fox jumps over the lazy cat.
The quick green fox jumps over the lazy cat.
The quick green fox jumps over the lazy cat.
The quick green fox jumps over the lazy cat.
The quick green fox jumps over the lazy cat.
[root@free ~]# cat data1.txt
The quick brown fox jumps over the lazy dog.
The quick brown fox jumps over the lazy dog.
The quick brown fox jumps over the lazy dog.
The quick brown fox jumps over the lazy dog.
The quick brown fox jumps over the lazy dog.
2、有-e直接空格分隔
[root@free ~]# sed -e 's/brown/green/' -e 's/dog/cat/' data1.txt
The quick green fox jumps over the lazy cat.
The quick green fox jumps over the lazy cat.
The quick green fox jumps over the lazy cat.
The quick green fox jumps over the lazy cat.
The quick green fox jumps over the lazy cat.3、还可以换行输入
[root@free ~]# sed -e '
s/brown/green/
s/dog/cat/
' data1.txt
The quick green fox jumps over the lazy cat.
The quick green fox jumps over the lazy cat.
The quick green fox jumps over the lazy cat.
The quick green fox jumps over the lazy cat.
The quick green fox jumps over the lazy cat.[root@free ~]# sed '{
> s/brown/green/
> s/dog/cat/
> }' data1.txt
The quick green fox jumps over the lazy cat.
The quick green fox jumps over the lazy cat.
The quick green fox jumps over the lazy cat.
The quick green fox jumps over the lazy cat.
The quick green fox jumps over the lazy cat
sed 编辑器基础
替换命令（s）与高级选项
-
语法：
-
注意：不管后面有没有新加参数都一定要分隔符（一般为/，但是分隔符可以自己定义，改为其他的也行）结尾
s/pattern/replace/[flags]flags替换标记：标记 描述 示例 数字 替换第 n处匹配s/test/trial/2：替换第 2 个testg全局替换所有匹配项 s/test/trial/g：替换所有testp打印匹配行（需 -n）sed -n 's/test/trial/p' data.txtw file将结果写入文件 sed 's/test/trial/w output.txt' data.txt
-
替换分隔符：
当模式含/时，可用其他字符（如!）替代分隔符：sed -n 's!/bin/bash!/bin/csh!p' /etc/passwd
使用地址（行寻址）
- 数字寻址：
- 单一行号：
2s/dog/cat/（修改第 2 行）； - 行区间：
2,3d（删除第 2-3 行）； - 从某行到末尾：
2,$s/old/new/（$代表末行）。
- 单一行号：
- 文本模式寻址：
sed -n '/redhat/s/bash/csh/p' /etc/passwd # 仅处理含"redhat"的行 - 命令组合：
sed '2{ > s/fox/elephant/ > s/dog/cat/ > }' data1.txt # 对第2行执行两条替换命令
删除命令（d）
- 按行号删除：
sed '3d' data4.txt # 删除第3行 - 按模式删除：
sed '/number 1/d' data4.txt # 删除含"number 1"的行 - 区间删除：
sed '/1/,/3/d' data4.txt # 删除包含"1"和"3"的行区间
插入与附加命令（i/a）（\）
- 插入命令（i）：在指定行前添加新行（分隔符用\）
[root@free ~]# sed '3i/hellow' data1.txt The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. /hellow The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog.[root@free ~]# sed '3i\hellow' data1.txt The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. hellow The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. - 附加命令（a）：在指定行后添加新行
[root@free ~]# sed '3a\hellow' data1.txt The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. hellow The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. - 行末附加：
[root@free ~]# sed '$a\hellow' data1.txt The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. hellow
修改命令（c）(\)
data4.txt
This is line number 1.
This is line number 2.
This is line number 3.
This is line number 4.- 按行号修改：
sed '3c\This is a changed line.' data4.txt # 修改第3行 - 按模式修改：
sed '/number 3/c\This is a changed line.' data4.txt
转换命令（y）
data5.txt
This is line number 1.
This is line number 2.
This is line number 3.
This is line number 4.
This is line number 1 again.
This is text you want to keep.
This is the last line in the file.- 字符一对一转换：
sed 'y/123/789/' data5.txt # 将"1"→"7"，"2"→"8"，"3"→"9" - 全局转换：自动转换所有匹配字符，无需指定位置。
打印命令（p、=、l）
p命令：打印匹配行（需-n）sed -n '/number 3/p' data4.txt=命令：打印行号sed '=' data1.txt # 输出行号与内容 [root@free ~]# sed '=' data1.txt 1 The quick brown fox jumps over the lazy dog. 2 The quick brown fox jumps over the lazy dog. 3 The quick brown fox jumps over the lazy dog. 4 The quick brown fox jumps over the lazy dog. 5 The quick brown fox jumps over the lazy dog.l命令：打印行及不可见字符（如制表符\t）
[root@free ~]# cat data6.txt
This line contains tabs.
-
sed -n 'l' data6.txt [root@free ~]# sed -n 'l' data6.txt This line contains tabs.$
文件操作命令（w/r）
- 写入文件（w）：
sed '1,2w test.txt' data4.txt # 将前两行写入test.txt - 读取文件（r）：在指定位置插入外部文件内容
sed '3r data8.txt' data4.txt # 在第3行后插入data8.txt内容
sed 案例
把/etc/passwd 复制到/root/test.txt，用sed打印所有行；
- 打印文件所有行：
sed -n '1,$p' test.txt - 删除含特定字符的行：
sed '/bash/d' test.txt - 替换路径字符串(改变分隔符即可)：
sed 's#/sbin/nologin#/bin/login#' test.txt - 提取目录名与基名：
echo "/etc/sysconfig/network-scripts/" | sed -r 's#^/(.*)/(.*)/#\1#' # 提取目录名 echo "/etc/sysconfig/network-scripts/" |sed -r 's#^/(.*)/(.*)/#\2#' #提取基名 .*是贪婪匹配，一直以匹配到最长，除非像以上后面还是字符限制如果只要取第一个目录名： [root@free ~]# echo "/etc/sysconfig/network-scripts/" | sed -r 's#^/([a-z]+)/(.*)/#\1#' etc（）定义捕获组，\1是将匹配到的内容替换为第一个捕获组所匹配到的内容 提取目录名还能用dirname dirname /etc/httpd/conf.d/host.conf基名能用basename basename /etc/httpd/conf.d/host.conf - 提取 IPv4 地址：
ifconfig | sed -n '2p' | sed -r "s/.*inet[[:space:]]*//; s/[[:space:]]*netmask.*//" 这是先取出第二行，然后将不需要的部分替换为空第二种方法 [root@free ~]# ifconfig | sed -rn 's/.*inet ([0-9.]+).*/\1/p' 192.168.153.135 127.0.0.1定义捕获组为ipv4的格式，也可以使用更具体的匹配格式 [root@free ~]# ifconfig | sed -rn 's/.*inet ([0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}).*/\1/p' 192.168.153.135 127.0.0.1如果想要去掉回环地址 [root@free ~]# ifconfig | sed -rn 's/.*inet ([0-9.]+).*/\1/p' | grep -v '^127' 192.168.153.135-v去掉满足要求的 - 在test.txt 20行到末行最前面加’aaa:’
sed '20,$s/^.*$/aaa:&/g' test.txt^.*$：正则表达式，匹配整行内容（^行首，.*任意字符，$行尾）。
aaa:&：替换文本，&是sed的特殊变量，表示匹配的内容（即整行）。7.复制/etc/grub2.cfg到/root/grub2.cfg,删除文件中所有以空白开头的行行首的空白字符；
sed 's/^\s*//' /etc/grub2.cfg
\s通常可以用来表示空白字符sed 's/^[[:space:]]//' grub2.cfg8.关闭selinux功能
就是用-i将文件直接修改
将SELINUX=.*替换为SELINUX=disabled
它配置文件有将3种不同形式列出来
# enforcing - SELinux security policy is enforced.
# permissive - SELinux prints warnings instead of enforcing.
# disabled - No SELinux policy is loaded.
[root@free ~]# cat /etc/selinux/config ....
SELINUX=enforcing
....[root@free ~]# sed -i 's/SELINUX=.*/SELINUX=disabled/' /etc/selinux/config
[root@free ~]# cat /etc/selinux/config # This file controls the state of SELinux on the system.
# SELINUX=disabled
# SELINUX=disabled
# enforcing - SELinux security policy is enforced.
# permissive - SELinux prints warnings instead of enforcing.
# disabled - No SELinux policy is loaded.
# See also:
# https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/9/html/using_selinux/changing-selinux-states-and-modes_using-selinux#changing-selinux-modes-at-boot-time_changing-selinux-states-and-modes
#
# NOTE: Up to RHEL 8 release included, SELINUX=disabled
# NOTE: Up to RHEL 8 release included, SELINUX=disabled
# fully disable SELinux during boot. If you need a system with SELinux
# fully disabled instead of SELinux running with no policy loaded, you
# need to pass selinux=0 to the kernel command line. You can use grubby
# to persistently set the bootloader to boot with selinux=0:
#
# grubby --update-kernel ALL --args selinux=0
#
# To revert back to SELinux enabled:
#
# grubby --update-kernel ALL --remove-args selinux
#
SELINUX=disabled
SELINUX=disabled
# SELINUXTYPE= can take one of these three values:
# targeted - Targeted processes are protected,
# minimum - Modification of targeted policy. Only selected processes are protected.
# mls - Multi Level Security protection.
SELINUXTYPE=targeted修改完配置文件后要将虚拟机重启才能生效，reboot
getenforce可以查看selinux状态