文本处理三剑客：
grep, egrep, fgrep：文本过滤器
sed：Stream EDitor，流编辑器，行
awk：文本格式化工具，报告生成器
sed [OPTION]... 'script' [input-file] ...
script组成格式：
地址定界编辑命令
OPTION：
-n：不输出模式空间中的内容至屏幕
-e script, --expression=script：多点编辑
-f /PATH/TO/SED_SCRIPT_FILE
SED_SCRIPT：每行一个编辑命令
-r, --regexp-extended：支持使用扩展正则表达式
-i[SUFFIX], --in-place[=SUFFIX]：直接编辑原文件
[root@promote ~]# sed -e 's@^#[[:space:]]*@@' -e '/^UUID/d' /etc/fstab
/etc/fstab
Created by anaconda on Sun Apr 14 09:29:51 2019
Accessible filesystems, by reference, are maintained under '/dev/disk'
See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
/dev/mapper/centos_promote-root / xfs defaults 0 0
/dev/mapper/centos_promote-home /home xfs defaults 0 0
/dev/mapper/centos_promote-swap swap swap defaults 0 0
地址定界：
(1) 空地址：对全文进行处理；
(2) 单地址：
#：指定行；
/pattern/：被此模式所匹配到的每一行；(3) 地址范围
#,#：
#,+#：
#，/pat1/
/pat1/,/pat2/
$：最后一行；(4) 步进：~
1~2：所有奇数行
2~2：所有偶数行
编辑命令：
d：删除
[root@promote ~]# cat /etc/fstab
#
# /etc/fstab
# Created by anaconda on Sun Apr 14 09:29:51 2019
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
/dev/mapper/centos_promote-root / xfs defaults 0 0
UUID=273deb66-d03c-457f-8b29-5df019b3e53a /boot xfs defaults 0 0
/dev/mapper/centos_promote-home /home xfs defaults 0 0
/dev/mapper/centos_promote-swap swap swap defaults 0 0
[root@promote ~]# sed '/^#/d' /etc/fstab
/dev/mapper/centos_promote-root / xfs defaults 0 0
UUID=273deb66-d03c-457f-8b29-5df019b3e53a /boot xfs defaults 0 0
/dev/mapper/centos_promote-home /home xfs defaults 0 0
/dev/mapper/centos_promote-swap swap swap defaults 0 0
p：显示模式空间中的内容
[root@promote ~]# sed '2~2p' /etc/fstab #偶数行会显示两遍
#
#
# /etc/fstab
# Created by anaconda on Sun Apr 14 09:29:51 2019
# Created by anaconda on Sun Apr 14 09:29:51 2019
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
#
/dev/mapper/centos_promote-root / xfs defaults 0 0
UUID=273deb66-d03c-457f-8b29-5df019b3e53a /boot xfs defaults 0 0
UUID=273deb66-d03c-457f-8b29-5df019b3e53a /boot xfs defaults 0 0
/dev/mapper/centos_promote-home /home xfs defaults 0 0
/dev/mapper/centos_promote-swap swap swap defaults 0 0
/dev/mapper/centos_promote-swap swap swap defaults 0 0
[root@promote ~]# sed -n '2~2p' /etc/fstab #显示所有的偶数行
#
# Created by anaconda on Sun Apr 14 09:29:51 2019
# Accessible filesystems, by reference, are maintained under '/dev/disk'
#
UUID=273deb66-d03c-457f-8b29-5df019b3e53a /boot xfs defaults 0 0
/dev/mapper/centos_promote-swap swap swap defaults 0 0
a \text：在行后面追加文本“text”，支持使用\n实现多行追加
[root@promote ~]# sed '3a \new line' /etc/fstab
#
# /etc/fstab
new line
# Created by anaconda on Sun Apr 14 09:29:51 2019
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
/dev/mapper/centos_promote-root / xfs defaults 0 0
UUID=273deb66-d03c-457f-8b29-5df019b3e53a /boot xfs defaults 0 0
/dev/mapper/centos_promote-home /home xfs defaults 0 0
/dev/mapper/centos_promote-swap swap swap defaults 0 0
[root@promote ~]# sed '3a \new line\nanother new line' /etc/fstab
#
# /etc/fstab
new line
another new line
# Created by anaconda on Sun Apr 14 09:29:51 2019
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
/dev/mapper/centos_promote-root / xfs defaults 0 0
UUID=273deb66-d03c-457f-8b29-5df019b3e53a /boot xfs defaults 0 0
/dev/mapper/centos_promote-home /home xfs defaults 0 0
/dev/mapper/centos_promote-swap swap swap defaults 0 0
i \text：在行前面插入文本“text”，支持使用\n实现多行插入
[root@promote ~]# sed '3i \new line' /etc/fstab
#
new line
# /etc/fstab
# Created by anaconda on Sun Apr 14 09:29:51 2019
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
/dev/mapper/centos_promote-root / xfs defaults 0 0
UUID=273deb66-d03c-457f-8b29-5df019b3e53a /boot xfs defaults 0 0
/dev/mapper/centos_promote-home /home xfs defaults 0 0
/dev/mapper/centos_promote-swap swap swap defaults 0 0
c \text：把匹配到的行替换为此处指定的文本“text”
[root@promote ~]# sed '4c \change line' /etc/fstab
#
# /etc/fstab
change line
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
/dev/mapper/centos_promote-root / xfs defaults 0 0
UUID=273deb66-d03c-457f-8b29-5df019b3e53a /boot xfs defaults 0 0
/dev/mapper/centos_promote-home /home xfs defaults 0 0
/dev/mapper/centos_promote-swap swap swap defaults 0 0
w /PATH/TO/SOMEFILE：保存模式空间匹配到的行至指定的文件中
[root@promote ~]# sed -n '/^[^#]/p' /etc/fstab
/dev/mapper/centos_promote-root / xfs defaults 0 0
UUID=273deb66-d03c-457f-8b29-5df019b3e53a /boot xfs defaults 0 0
/dev/mapper/centos_promote-home /home xfs defaults 0 0
/dev/mapper/centos_promote-swap swap swap defaults 0 0
[root@promote ~]# sed '/^[^#]/w /tmp/fstab.new' /etc/fstab
#
# /etc/fstab
# Created by anaconda on Sun Apr 14 09:29:51 2019
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
/dev/mapper/centos_promote-root / xfs defaults 0 0
UUID=273deb66-d03c-457f-8b29-5df019b3e53a /boot xfs defaults 0 0
/dev/mapper/centos_promote-home /home xfs defaults 0 0
/dev/mapper/centos_promote-swap swap swap defaults 0 0
[root@promote ~]# cat /tmp/fstab.new
/dev/mapper/centos_promote-root / xfs defaults 0 0
UUID=273deb66-d03c-457f-8b29-5df019b3e53a /boot xfs defaults 0 0
/dev/mapper/centos_promote-home /home xfs defaults 0 0
/dev/mapper/centos_promote-swap swap swap defaults 0 0
r /PATH/FROM/SOMEFILE：读取指定文件的内容至当前文件被模式匹配到的行后面；文件合并；
[root@promote ~]# sed '3r /etc/issue' /etc/fstab
#
# /etc/fstab
\S
Kernel \r on an \m
# Created by anaconda on Sun Apr 14 09:29:51 2019
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
/dev/mapper/centos_promote-root / xfs defaults 0 0
UUID=273deb66-d03c-457f-8b29-5df019b3e53a /boot xfs defaults 0 0
/dev/mapper/centos_promote-home /home xfs defaults 0 0
/dev/mapper/centos_promote-swap swap swap defaults 0 0
=：为模式匹配到的行打印行号
[root@promote ~]# sed '/^UUID/=' /etc/fstab
#
# /etc/fstab
# Created by anaconda on Sun Apr 14 09:29:51 2019
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
/dev/mapper/centos_promote-root / xfs defaults 0 0
10
/dev/mapper/centos_promote-root / xfs defaults 0 0
11
UUID=273deb66-d03c-457f-8b29-5df019b3e53a /boot xfs defaults 0 0
/dev/mapper/centos_promote-home /home xfs defaults 0 0
/dev/mapper/centos_promote-swap swap swap defaults 0 0
!：条件取反
格式：地址定界!编辑命令
[root@promote ~]# sed '/^#/!d' /etc/fstab
#
# /etc/fstab
# Created by anaconda on Sun Apr 14 09:29:51 2019
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
s///：查找替换，其分隔符可自行指定，常用的有s@@@, s###等
替换标记：
g：全局替换
w /PATH/TO/SOMEFILE：将替换成功的结果保存至指定文件中
p：显示替换成功的行
练习1：删除/boot/grub/grub2.cfg文件中所有以空白字符开头的行的行首的所有空白字符；
[root@promote ~]# sed 's@^[[:space:]]\+@@' /etc/grub2.cfg
练习2：删除/etc/fstab文件中所有以#开头的行的行首的#号及#后面的所有空白字符；
[root@promote ~]# sed 's@^#[[:space:]]*@@' /etc/fstab
练习3：输出一个绝对路径给sed命令，取出其目录，其行为类似于dirname；
[root@promote ~]# echo "/var/log/messages/" | sed 's@[^/]\+/\?$@@'
[root@promote ~]# echo "/var/log/messages" | sed -r 's@[^/]+/?$@@'
高级编辑命令：
h：把模式空间中的内容覆盖至保持空间中；
H：把模式空间中的内容追加至保持空间中；
g：把保持空间中的内容覆盖至模式空间中；
G：把保持空间中的内容追加至模式空间中；
x：把模式空间中的内容与保持空间中的内容互换；
n：覆盖读取匹配到的行的下一行至模式空间中；
N：追加读取匹配到的行的下一行至模式空间中；
d：删除模式空间中的行；
D：删除多行模式空间中的所有行；
示例：
sed -n 'n;p' FILE：显示偶数行；
sed '1!G;h;$!d' FILE：逆序显示文件的内容；
sed ’$!d' FILE：取出最后一行；
sed '$!N;$!D' FILE：取出文件后两行；
sed '/^$/d;G' FILE：删除原有的所有空白行，而后为所有的非空白行后添加一个空白行；
sed 'n;d' FILE：显示奇数行；
sed 'G' FILE：在原有的每行后方添加一个空白行；
练习：用bash实现统计访问日志文件中状态码大于等于400的IP数量并排序
[root@localhost ~]# cat nginx_access_log | cut -d' ' -f1,9 | grep '\<[4-9][0-9][0-9]\>' | cut -d' ' -f1 | sort | uniq -c | sort -r
7 100.109.195.28
4 100.109.195.26
2 100.109.195.27