简述systemd的新特性及unit常见类型分析，能够实现编译安装的如nginx\apache实现通过systemd来管理
systemd是cenos7版本新引入的系统级服务管理工具，其主要的新特性如下：
- 系统引导时实现服务并行启动
- 按需激活进程（默认情况并没有实际启动进程）
- 支持系统状态快照
- 基于依赖关系来自定义服务的控制逻辑
systemd的核心概念就是unit（单元），将不同的管理资源称之为unit。通过配置文件来进行标识，识别和配置，文件包含了系统服务，监听的套接字文件（socket）及init相关的信息等等。配置文件主要有以下几下：
- /usr/lib/systemd/system
- /run/systemd/system
- /etc/systemd/system
- /lib/systemd/system
unit的常见类型：
Service unit：文件扩展名为.service，用于定义系统服务，如：httpd.service
Target unit：文件扩展为.target，用于模拟实现“运行级别”；
Device unit： .device，用于定义内核识别的设备；
Mount unit： .mount，定义文件系统挂载点；
Socket unit： .socket，用于标识进程间通信用到的socket（套接字）文件；
Snapshot unit： .snapshot， 管理系统快照；
Swap unit： .swap, 用于标识swap（交换分区）设备；
Automount unit： .automount，文件系统自动点设备；
Path unit： .path, 用于定义文件系统中的一文件或目录（在某些特殊的情况下使用
[root@zcy520ooooo ~]# ls /usr/lib/systemd/system
arp-ethers.service rhel-autorelabel-mark.service
auditd.service rhel-autorelabel.service
autovt@.service rhel-configure.service
basic.target rhel-dmesg.service
basic.target.wants rhel-domainname.service
blk-availability.service rhel-import-state.service
bluetooth.target rhel-loadmodules.service
brandbot.path rhel-readonly.service
brandbot.service rpcbind.target
......#以下省略
systemd关键特性工作原理：
1.基于sokcet的激活机制：
在系统引导时systemd会为所有支持激活该类型的服务分别创建一个socket，并在系统启动后将这个socket传给该服务，实现系统并行启动，并且可以在服务未启动时用systemd去监听这个socket的状态，当有进程访问这个socket时systemd在启动该服务，实现socket与服务程序的分离。
2. 基于bus的激活机制：
通过监听bus的状态来启动相应服务。
3. 基于device的激活机制：
在某个硬件设备激活或变为可用时，激活相应服务。
4. 基于Path的激活机制：
在文件路径变为可用或有文件时，激活相应服务。
5. 系统快照：
保存各unit的当前状态信息于持久存储设备中，随后服务启动时可用从快照开始继续运行。
6. 向后兼容sysv init脚本：
兼容性有限，不建议centos7中在使用init命令。
7. 不兼容：
systemctl的命令格式是固定不变的，不是由systemd启动的服务，systemd无法与之通信，systemctl不会与任何标准输入流有交流，自行控制其服务的启动。（不能通过交互方式去干涉systemd启动的服务，只能选择用systemd去开启，关闭服务等等。）
管理系统服务：
systemctl命令： Control the systemd system and service manager（控制systemd系统和其服务管理命令）
centos7：service类型的unit文件
systemctl [OPTIONS...] COMMAND [NAME...].service
COMMAND：
启动： service NAME start ==> systemctl start NAME.service
停止： service NAME stop ==> systemctl stop NAME.service
重启： service NAME restart ==> systemctl restart NAME.service
状态： service NAME status ==> systemctl status NAME.service
条件式重启：service NAME condrestart ==> systemctl try-restart NAME.service
重载或重启服务： systemctl reload-or-restart NAME.servcie
重载或条件式重启服务：systemctl reload-or-try-restart NAME.service
查看某服务当前激活与否的状态： systemctl is-active NAME.service
查看所有已激活的服务：systemctl list-units --type service
查看所有服务（已激活及未激活）: chkconfig --lsit ==> systemctl list-units -t service --all
设置服务开机自启： chkconfig NAME on ==> systemctl enable NAME.service
禁止服务开机自启： chkconfig NAME off ==> systemctl disable NAME.service
查看某服务是否能开机自启： chkconfig --list NAME ==> systemctl is-enabled NAME.service
禁止某服务设定为开机自启： systemctl mask NAME.service
取消此禁止： systemctl unmask NAME.servcie
查看服务的依赖关系：systemctl list-dependencies NAME.service
[root@zcy520ooooo ~]# systemctl list-units -t service --all
UNIT LOAD ACTIVE SUB DESCRIPTION
auditd.service loaded active running Security Auditing Service
chronyd.service loaded active running NTP client/server
cpupower.service loaded inactive dead Configure CPU power related settin
crond.service loaded active running Command Scheduler
dbus.service loaded active running D-Bus System Message Bus
● display-manager.service not-found inactive dead display-manager.service
dracut-shutdown.service loaded inactive dead Restore /run/initramfs
ebtables.service loaded inactive dead Ethernet Bridge Filtering tables
emergency.service loaded inactive dead Emergency Shell
● exim.service not-found inactive dead exim.service
firewalld.service loaded active running firewalld - dynamic firewall daemo
getty@tty1.service loaded active running Getty on tty1
httpd.service loaded active running The Apache HTTP Server
● ip6tables.service not-found inactive dead ip6tables.service
● ipset.service not-found inactive dead ipset.service
● iptables.service not-found inactive dead iptables.service
irqbalance.service loaded active running irqbalance daemon
● kdump.service loaded failed failed Crash recovery kernel arming
kmod-static-nodes.service loaded active exited Create list of required static dev
microcode.service loaded inactive dead Load CPU microcode update
network.service loaded active exited LSB: Bring up/down networking
NetworkManager-wait-online.service loaded active exited Network Manager Wait Online
NetworkManager.service loaded active running Network Manager
...#以下很多省略
============================================华丽的分割线===============================================
[root@zcy520ooooo ~]# systemctl status httpd
● httpd.service - The Apache HTTP Server
Loaded: loaded (/usr/lib/systemd/system/httpd.service; disabled; vendor preset: disabled)
Active: active (running) since 四 2018-10-11 13:47:24 CST; 2h 34min ago
Docs: man:httpd(8)
man:apachectl(8)
Main PID: 9184 (httpd)
Status: "Total requests: 0; Current requests/sec: 0; Current traffic: 0 B/sec"
CGroup: /system.slice/httpd.service
├─9184 /usr/sbin/httpd -DFOREGROUND
├─9186 /usr/sbin/httpd -DFOREGROUND
├─9187 /usr/sbin/httpd -DFOREGROUND
├─9188 /usr/sbin/httpd -DFOREGROUND
├─9189 /usr/sbin/httpd -DFOREGROUND
└─9190 /usr/sbin/httpd -DFOREGROUND
10月 11 13:47:23 zcy520ooooo systemd[1]: Starting The Apache HTTP Server...
10月 11 13:47:24 zcy520ooooo httpd[9184]: AH00558: httpd: Could not reliably determine the ser...age
10月 11 13:47:24 zcy520ooooo systemd[1]: Started The Apache HTTP Server.
Hint: Some lines were ellipsized, use -l to show in full.
管理target units：
target units用来模拟实现运行级别，target units与init运行级别的对应关系，级别切换，查看等命令：
0 ==> runlevel0.target, poweroff.target
1 ==> runlevel1.target, rescue.target
2 ==> runlevel2.tartet, multi-user.target
3 ==> runlevel3.tartet, multi-user.target
4 ==> runlevel4.tartet, multi-user.target
5 ==> runlevel5.target, graphical.target
6 ==> runlevel6.target, reboot.target
级别切换： init N ==> systemctl isolate NAME.target
查看级别： runlevel ==> systemctl list-units --type target
查看所有级别： systemctl list-units -t target -a
获取默认运行级别：systemctl get-default
修改默认运行级别： systemctl set-default NAME.target
切换至紧急救援模式： systemctl rescue
切换至emergency模式： systemctl emergency
其它常用命令：
关机： systemctl halt, systemctl poweroff
重启： systemctl reboot
挂起： systemctl suspend
快照： systemctl hibernate
快照并挂起： systemctl hybrid-sleep
[root@zcy520ooooo ~]# systemctl get-default
multi-user.target
service unit file:
文件通常由[Unit],[Service],[Install]三部分组成:
[root@zcy520ooooo ~]# cd /usr/lib/systemd/system
[root@zcy520ooooo system]# cat httpd.service
[Unit]
Description=The Apache HTTP Server
After=network.target remote-fs.target nss-lookup.target
Documentation=man:httpd(8)
Documentation=man:apachectl(8)
[Service]
Type=notify
EnvironmentFile=/etc/sysconfig/httpd
ExecStart=/usr/sbin/httpd $OPTIONS -DFOREGROUND
ExecReload=/usr/sbin/httpd $OPTIONS -k graceful
ExecStop=/bin/kill -WINCH ${MAINPID}
# We want systemd to give httpd some time to finish gracefully, but still want
# it to kill httpd after TimeoutStopSec if something went wrong during the
# graceful stop. Normally, Systemd sends SIGTERM signal right after the
# ExecStop, which would kill httpd. We are sending useless SIGCONT here to give
# httpd time to finish.
KillSignal=SIGCONT
PrivateTmp=true
[Install]
WantedBy=multi-user.target
Unit:定义与Unit类型无关的通用选项；用于提供unit的描述信息、unit行为及依赖关系等
Unit段的常用选项：
Description：描述信息； 意义性描述；
After：定义unit的启动次序；表示当前unit应该晚于哪些unit启动；其功能与Before相反；
Requies：依赖到的其它units；强依赖，被依赖的units无法激活时，当前unit即无法激活；
Wants：依赖到的其它units；弱依赖；
Conflicts：定义units间的冲突关系；
Service：与特定类型相关的专用选项；此处为Service类型
Service段的常用选项：
Type：用于定义影响ExecStart及相关参数的功能的unit进程启动类型；
类型：
simple：由ExecStart启动的进程为该程序的主进程
forking：由ExecStart指明的程序启动的进程的子进程会成为主进程,且生成之后主进程会退出
oneshot：一次性的主进程类似simple,但启动后续unit之前主进程会退出
dbus：类似simple,后续的unit在当前的unit得到dbus名称之后才能启动
notify：类似于simple,后续的unit在通过sdnotify函数发送通知,才能启动
idle：类似simple
EnvironmentFile：环境配置文件；在ExecStart之前读取并为其提供某些变量
ExecStart：指明启动unit要运行命令或脚本；
ExecStartPre：指明启动unit要运行之前命令或脚本
ExecStartPost指明启动unit要运行之后命令或脚本
ExecStop：指明停止unit要运行的命令或脚本；
Restart：指明重启unit要运行的命令或脚本
Install：定义由“systemctl enable”以及"systemctl disable“命令在实现服务启用或禁用时用到的一些选项
Install段的常用选项：
Alias：
RequiredBy：被哪些units所依赖；
WantedBy：被哪些units所依赖
注意：对于新创建的unit文件或，修改了的unit文件，要通知systemd重载此配置文件
systemctl daemon-reload
实现编译安装的如nginx\apache实现通过systemd来管理:
- 安装编译安装依赖的类库和包
[root@zcy520ooooo ~]# yum install gcc gcc-c++ autoconf automake zlib zlib-devel openssl openssl-devel pcre-devel
#安装过程已省略
已安装:
openssl-devel.x86_64 1:1.0.2k-12.el7 pcre-devel.x86_64 0:8.32-17.el7
作为依赖被安装:
keyutils-libs-devel.x86_64 0:1.5.8-3.el7 krb5-devel.x86_64 0:1.15.1-19.el7
libcom_err-devel.x86_64 0:1.42.9-12.el7_5 libselinux-devel.x86_64 0:2.5-12.el7
libsepol-devel.x86_64 0:2.5-8.1.el7 libverto-devel.x86_64 0:0.2.5-4.el7
作为依赖被升级:
e2fsprogs.x86_64 0:1.42.9-12.el7_5 e2fsprogs-libs.x86_64 0:1.42.9-12.el7_5
libcom_err.x86_64 0:1.42.9-12.el7_5 libss.x86_64 0:1.42.9-12.el7_5
完毕！
- 下载并解压nginx
[root@zcy520ooooo ~]# wget http://nginx.org/download/nginx-1.11.10.tar.gz
--2018-10-17 18:01:22-- http://nginx.org/download/nginx-1.11.10.tar.gz
正在解析主机 nginx.org (nginx.org)... 206.251.255.63, 95.211.80.227, 2606:7100:1:69::3f, ...
正在连接 nginx.org (nginx.org)|206.251.255.63|:80... 已连接。
已发出 HTTP 请求，正在等待回应... 200 OK
长度：967773 (945K) [application/octet-stream]
正在保存至: “nginx-1.11.10.tar.gz”
100%[===========================================================>] 967,773 369KB/s 用时 2.6s
2018-10-17 18:01:25 (369 KB/s) - 已保存 “nginx-1.11.10.tar.gz” [967773/967773])
---------------------------------分割线----------------------------------------------------------------
[root@zcy520ooooo ~]# tar xf nginx-1.11.10.tar.gz
[root@zcy520ooooo ~]# ls
nginx-1.11.10.tar.gz nginx-1.11.10
[root@zcy520ooooo ~]# cd nginx-1.11.10
[root@zcy520ooooo nginx-1.11.10]#
- 编译安装Nginx
[root@zcy520ooooo nginx-1.11.10]# ./configure
checking for OS
+ Linux 3.10.0-862.el7.x86_64 x86_64
checking for C compiler ... found
+ using GNU C compiler
+ gcc version: 4.8.5 20150623 (Red Hat 4.8.5-28) (GCC)
checking for gcc -pipe switch ... found
checking for -Wl,-E switch ... found
checking for gcc builtin atomic operations ... found
checking for C99 variadic macros ... found
#中间省略......
creating objs/Makefile
Configuration summary
+ using system PCRE library
+ OpenSSL library is not used
+ using system zlib library
nginx path prefix: "/usr/local/nginx"
nginx binary file: "/usr/local/nginx/sbin/nginx"
nginx modules path: "/usr/local/nginx/modules"
nginx configuration prefix: "/usr/local/nginx/conf"
nginx configuration file: "/usr/local/nginx/conf/nginx.conf"
nginx pid file: "/usr/local/nginx/logs/nginx.pid"
nginx error log file: "/usr/local/nginx/logs/error.log"
nginx http access log file: "/usr/local/nginx/logs/access.log"
nginx http client request body temporary files: "client_body_temp"
nginx http proxy temporary files: "proxy_temp"
nginx http fastcgi temporary files: "fastcgi_temp"
nginx http uwsgi temporary files: "uwsgi_temp"
nginx http scgi temporary files: "scgi_temp
[root@zcy520ooooo nginx-1.11.10]# make && make install
make -f objs/Makefile
make[1]: 进入目录“/root/nginx-1.11.10”
cc -c -pipe -O -W -Wall -Wpointer-arith -Wno-unused-parameter -Werror -g -I src/core -I src/event -I src/event/modules -I src/os/unix -I objs \
-o objs/src/core/nginx.o \
src/core/nginx.c
cc -c -pipe -O -W -Wall -Wpointer-arith -Wno-unused-parameter -Werror -g -I src/core -I src/event -I src/event/modules -I src/os/unix -I objs \
-o objs/src/core/ngx_log.o \
src/core/ngx_log.c
cc -c -pipe -O -W -Wall -Wpointer-arith -Wno-unused-parameter -Werror -g -I src/core -I src/event -I src/event/modules -I src/os/unix -I objs \
-o objs/src/core/ngx_palloc.o \
#......中间过程省略
- 配置systemd Nginx服务和设置Nginx自启动
创建systemd服务文件：/lib/systemd/system/nginx.service内容如下：
[root@zcy520ooooo system]# vim nginx.service
[Unit]
Description=nginx
After=network.target
[Service]
Type=forking
ExecStart=/usr/local/nginx/sbin/nginx
ExecReload=/usr/local/nginx/sbin/nginx -s reload
ExecStop=/usr/local/nginx/sbin/nginx -s stop
PrivateTmp=true
[Install]
WantedBy=multi-user.target
- 重载配置文件并使用systemctl命令启动nginx服务
[root@zcy520ooooo system]# systemctl daemon-reload
[root@zcy520ooooo system]# systemctl start nginx.service
[root@zcy520ooooo system]# systemctl status nginx.service
● nginx.service - nginx
Loaded: loaded (/usr/lib/systemd/system/nginx.service; disabled; vendor preset: disabled)
Active: active (running) since 四 2018-10-18 10:02:50 CST; 1min 15s ago
Main PID: 4853 (nginx)
CGroup: /system.slice/nginx.service
├─4853 nginx: master process /usr/local/nginx/sbin/nginx
└─4854 nginx: worker proces
10月 18 10:02:50 localhost.localdomain systemd[1]: Starting nginx...
10月 18 10:02:50 localhost.localdomain systemd[1]: Started nginx.
提示:本实验只是演示如何用systemctl管理源码包编译的nginx服务,使用默认编译安装,uint配置文件也是相当简单,实际应用还需要做相应的调整
描述awk命令用法及示例(至少3例)
awk是文档的报告生成工具,主要用来格式化文本输出.有awk和gawk两个版本,linux上是gawk版本.awk一次从文本中读取一行,然后对该行按输入分隔符进行切片处理.默认分隔符为空白符.把分出来的每一片到保存到awk内建的变量中,1代表第一块切片....$n.最后对其中的某些片段进行过滤,显示等等其他一些操作.
基本用法：
gawk - pattern scanning and processing language
gawk [options] 'program' FILE ...
program: PATTERN{ACTION STATEMENTS}
语句之间用分号分隔
选项：
-F：指明输入时用到的字段分隔符；
-v var=value: 自定义变量,变量名严格区分字符大小写，并且可以program中直接定义。
[root@zcy520ooooo ~]# tail -4 /etc/fstab | awk ' {print $1,$3}'
UUID=17c90f0e-0bf0-40ea-8a5e-9598aa668053 xfs
UUID=7b58779e-372e-4096-8bbd-625b09e1a14e xfs
UUID=e4af4f09-a39e-4acf-b85d-4d4d9b41f584 xfs
UUID=6206b8c1-adeb-4fef-b197-a97df129e85e swap
1. print
print item1, item2, ...
使用要点：
(1)item之间用逗号分隔符
(2)输出的各item可以字符串，也可以是数值；当前记录的字段、变量或awk的表达式
(3)如省略item，相当于print $0
(4)awk中引用变量一般不用" "双引号或者$来引用
[root@zcy520ooooo ~]# tail -4 /etc/fstab | awk ' {print 123,$2,$3}'
123 / xfs
123 /boot xfs
123 /home xfs
123 swap swap
2. 常用的内建变量:
FS：input field seperator，输入字段分隔符，默认为空白字符
OFS：output field seperator，输出字段分隔符，默认为空白字符
RS：input record seperator，输入时的换行符
ORS：output record seperator，输出时的换行符，默认是回车
NF：number of field，每行的字段数量，{print NF}表示字段数量, {print $NF}代表最后一个字段
NR：number of record, 行数
FNR：各文件分别计数；行数
FILENAME：当前文件名
ARGC：命令行参数的个数
ARGV：数组，保存的是命令行所给定的各参数
[root@zcy520ooooo ~]# awk -v FS=':' -v OFS=':' '{print $2,$4}' /etc/passwd | tail -5
x:983
x:982
x:70
x:16
x:72
[root@zcy520ooooo ~]# awk -v FS=':' '{print $2,$4}' /etc/passwd | tail -5
x 983
x 982
x 70
x 16
x 72
------------------------------------------分割线--------------------------------------------------------
[root@zcy520ooooo ~]# awk '{print NF,$NF}' /etc/fstab
0
1 #
2 /etc/fstab
10 2018
1 #
9 '/dev/disk'
12 info
1 #
6 0
6 0
6 0
6 0
------------------------------------------分割线--------------------------------------------------------
[root@zcy520ooooo ~]# awk 'BEGIN{print ARGV[0]}' /etc/fstab
awk #把awk自身当作一个参数
[root@zcy520ooooo ~]# awk 'BEGIN{print ARGV[1]}' /etc/fstab
/etc/fstab
3. printf命令
格式化输出：printf FORMAT, item1, item2, ...
(1) FORMAT必须给出; FORMAT为每个item提供一种格式,并对应给出一个字段
(2) 不会自动换行，需要显式给出换行控制符，\n
(3) FOMAT中需要分别为后面的每个item指定一个格式化符号
格式符：
%c: 显示字符的ASCII码；
%d, %i: 显示十进制整数；
%e, %E: 科学计数法数值显示；
%f：显示为浮点数；
%g, %G：以科学计数法或浮点形式显示数值；
%s：显示字符串；
%u：无符号整数；
%%: 显示%自身；
修饰符：
#[.#]：第一个数字控制显示的宽度；第二个#表示小数点后的精度；
%3.1f
-: 左对齐
+：显示数值的符号
[root@zcy520ooooo ~]# awk -F: '{printf "%-20s:%3.2f\n", $1,$3}' /etc/passwd
root :0.00
bin :1.00
daemon :2.00
adm :3.00
lp :4.00
sync :5.00
shutdown :6.00
halt :7.00
mail :8.00
operator :11.00
games :12.00
ftp :14.00
nobody :99.00
systemd-network :192.00
dbus :81.00
polkitd :999.00
sshd :74.00
postfix :89.00
chrony :998.00
tss :59.00
apache :48.00
1 :1010.00
geoclue :997.00
logstash :1011.00
unbound :996.00
rpc :32.00
gluster :995.00
setroubleshoot :994.00
libstoragemgmt :993.00
usbmuxd :113.00
qemu :107.00
saslauth :992.00
radvd :75.00
ntp :38.00
rtkit :172.00
abrt :173.00
colord :991.00
pulse :171.00
gdm :42.00
rpcuser :29.00
nfsnobody :65534.00
sssd :990.00
gnome-initial-setup :989.00
pcp :988.00
avahi :70.00
oprofile :16.00
tcpdump :72.00
4. 操作符
awk支持常用的操作符,如:算术操作符,字符串操作符,赋值操作符,比较操作符,模式匹配符,逻辑操作符等等
算术操作符：
x+y, x-y, x*y, x/y, x^y, x%y
-x
+x: 转换为数值
字符串操作符：没有符号的操作符，字符串连接
赋值操作符：
=, +=, -=, *=, /=, %=, ^=
++, --
比较操作符：
>, >=, <, <=, !=, ==
模式匹配符：
~：是否匹配
!~：是否不匹配
逻辑操作符：
&&
||
!
函数调用：
function_name(argu1, argu2, ...)
条件表达式：
selector?if-true-expression:if-false-expression
[root@zcy520ooooo ~]# awk -F: '{print $3,$4}' /etc/passwd | tail -5
989 983
988 982
70 70
16 16
72 72
[root@zcy520ooooo ~]# awk -F: '{print $3+$4}' /etc/passwd | tail -5
1972
1970
140
32
144
------------------------------------------分割线--------------------------------------------------------
[root@zcy520ooooo ~]# awk -F: '{$1~"root"?usertype="root":usertype="common user or sysuser";printf "%
20s:%-s\n",$1,usertype}' /etc/passwd
root:root
bin:common user or sysuser
daemon:common user or sysuser
adm:common user or sysuser
lp:common user or sysuser
sync:common user or sysuser
shutdown:common user or sysuser
halt:common user or sysuser
mail:common user or sysuser
operator:common user or sysuser
games:common user or sysuser
ftp:common user or sysuser
nobody:common user or sysuser
systemd-network:common user or sysuser
dbus:common user or sysuser
polkitd:common user or sysuser
sshd:common user or sysuser
postfix:common user or sysuser
chrony:common user or sysuser
tss:common user or sysuser
apache:common user or sysuser
1:common user or sysuser
geoclue:common user or sysuser
logstash:common user or sysuser
unbound:common user or sysuser
rpc:common user or sysuser
gluster:common user or sysuser
setroubleshoot:common user or sysuser
libstoragemgmt:common user or sysuser
usbmuxd:common user or sysuser
qemu:common user or sysuser
saslauth:common user or sysuser
radvd:common user or sysuser
ntp:common user or sysuser
rtkit:common user or sysuser
abrt:common user or sysuser
colord:common user or sysuser
pulse:common user or sysuser
gdm:common user or sysuser
rpcuser:common user or sysuser
nfsnobody:common user or sysuser
sssd:common user or sysuser
gnome-initial-setup:common user or sysuser
pcp:common user or sysuser
avahi:common user or sysuser
oprofile:common user or sysuser
tcpdump:common user or sysuser
5. PATTERN匹配模式
awk默认匹配每一行,启动地址定界的功能
(1) empty：空模式，匹配每一行；
(2) /regular expression/：仅处理能够被此处的模式匹配到的行；
(3) relational expression: 关系表达式；结果有“真”有“假”；结果为“真”才会被处理；
(真：结果为非0值，非空字符串；)
(4) line ranges：行范围，
startline,endline：/pat1/,/pat2/
注意： 不支持直接给出数字的格式
(5) BEGIN/END模式
BEGIN{}: 仅在开始处理文件中的文本之前执行一次；
END{}：仅在文本处理完成之后执行一次；
[root@zcy520ooooo ~]# awk -F: '$NF~/bash$/ {print $1,$NF}' /etc/passwd
root /bin/bash
1 /bin/bash
logstash /bin/bash
#$NF~/bash$/:判断最后一个字段是否等于bash,等于则输出
------------------------------------------分割线--------------------------------------------------------
[root@zcy520ooooo ~]# awk -F: '/^h/,/^g/{print $1,$3}' /etc/passwd
halt 7
mail 8
operator 11
games 12
#匹配以h或以g开头的行
------------------------------------------分割线-------------------------------------------------------
[root@zcy520ooooo ~]# awk -F: 'BEGIN{print " username uid \n====================="}/^h/,/^g/{print $1,$3}END{print "-----------------------\n end "}' /etc/passwd
username uid
=====================
halt 7
mail 8
operator 11
games 12
-----------------------
end
6. 常用的action
(1) Expressions
(2) Control statements：控制语句,if, while等；
(3) Compound statements：组合语句；
(4) input statements:输入语句
(5) output statements:输出语句(print,printf)
[root@zcy520ooooo ~]# awk -F: '{for(i=1;i<NF;i++) {count[$i]++}}END{for(j in count) {print j,count[j]}}' /etc/passwd
rpc 1
10
adm 2
/var/spool/postfix 1
990 2
/var/ftp 1
991 2
/etc/ntp 1
992 2
993 1
994 1
Privilege-separated SSH 1
/bin 1
65534 2
113 2
995 2
radvd 1
996 2
997 1
/var/lib/chrony 1
sync 2
998 2
mail 2
999 1
daemon account for libstoragemgmt 1
/var/lib/pcp 1
tss 1
/dev/null 1
/var/run/gluster 1
gluster 1
/var/lib/setroubleshoot 1
logstash 1
/var/spool/lpd 1
171 2
172 2
Apache 1
173 2
unbound 1
systemd-network 1
11 1
halt 2
12 2
Performance Co-Pilot 1
/run/gnome-initial-setup/ 1
/proc 1
/usr/games 1
14 1
Unbound DNS resolver 1
192 2
16 2
32 2
/var/lib/nfs 2
postfix 1
System message bus 1
gdm 1
ntp 1
/sbin 4
50 1
38 2
avahi 1
/ 9
daemon 2
colord 1
/var/run/lsm 1
/var/empty/sshd 1
0 6
1 3
70 2
sssd 1
2 2
3 1
72 2
GlusterFS daemons 1
apache 1
59 2
systemd Network Management 1
4 2
/var/run/avahi-daemon 1
User for sssd 1
5 1
usbmuxd user 1
74 2
6 1
radvd user 1
75 2
7 2
shutdown 2
76 1
8 1
libstoragemgmt 1
/var/adm 1
User for geoclue 1
FTP User 1
PulseAudio System Daemon 1
gnome-initial-setup 1
982 1
/var/lib/rpcbind 1
geoclue 1
100 1
Avahi mDNS/DNS-SD Stack 1
983 1
pulse 1
setroubleshoot 1
/usr/share/httpd 1
984 1
99 2
/root 2
operator 2
/run/saslauthd 1
987 1
988 1
Anonymous NFS User 1
rtkit 1
/var/lib/geoclue 1
RealtimeKit 1
107 2
989 2
ftp 1
abrt 1
sshd 1
qemu user 1
qemu 1
oprofile 1
/var/lib/gdm 1
usbmuxd 1
/etc/unbound 1
RPC Service User 1
Account used by the trousers package to sandbox the tcsd daemon 1
/var/spool/mail 1
rpcuser 1
chrony 1
/var/lib/colord 1
dbus 1
saslauth 1
root 2
/etc/abrt 1
1010 2
Special user account to be used by OProfile 1
1011 2
tcpdump 1
pcp 1
nfsnobody 1
29 2
42 2
User for colord 1
games 2
Saslauthd user 1
Rpcbind Daemon 1
Nobody 1
lp 2
bin 2
48 2
User for polkitd 1
/home/logstash 1
/home/1 1
/var/run/pulse 1
81 2
nobody 1
polkitd 1
x 47
/var/lib/oprofile 1
89 2
$i表示该字段的值,如i=1,则$1=rpc,后面的j表示表示如果j在count[j]这个数组中,就打印以索引和对应的索引值,
如:i=1,count[$i]++相当于count[rpc]++,j in count表示j=rpc,并输出count[rpc]的值
7. 控制语句
awk可以在处理动作中加入判断,循环等控制语句,来对匹配到的字段进行处理.常见的控制语句如下:
if(condition) {statments} :对awk取得的整行或某个字段做条件判断
if(condition) {statments} else {statements}同上
语法：if(condition) statement [else statement]
[root@zcy520ooooo ~]# awk -F: '{if($3<=1000) {printf "root or sys user: %10s\n",$1} else {printf "common user: %10s\n",$1}}' /etc/passwd
root or sys user: root
root or sys user: bin
root or sys user: daemon
root or sys user: adm
root or sys user: lp
root or sys user: sync
root or sys user: shutdown
root or sys user: halt
root or sys user: mail
root or sys user: operator
root or sys user: games
root or sys user: ftp
root or sys user: nobody
root or sys user: systemd-network
root or sys user: dbus
root or sys user: polkitd
root or sys user: sshd
root or sys user: postfix
root or sys user: chrony
root or sys user: tss
root or sys user: apache
common user: 1
root or sys user: geoclue
common user: logstash
root or sys user: unbound
root or sys user: rpc
root or sys user: gluster
root or sys user: setroubleshoot
root or sys user: libstoragemgmt
root or sys user: usbmuxd
root or sys user: qemu
root or sys user: saslauth
root or sys user: radvd
root or sys user: ntp
root or sys user: rtkit
root or sys user: abrt
root or sys user: colord
root or sys user: pulse
root or sys user: gdm
root or sys user: rpcuser
common user: nfsnobody
root or sys user: sssd
root or sys user: gnome-initial-setup
root or sys user: pcp
root or sys user: avahi
root or sys user: oprofile
root or sys user: tcpdump
while(conditon) {statments}:对一行内的多个字段逐一类似处理时使用; 对数组中的各元素逐一处理时使用
语法：while(condition) statement
条件“真”，进入循环；条件“假”，退出循环
[root@zcy520ooooo ~]# awk '/^[[:space:]]*linux16/{i=1;while(i<=NF) {print $i,length($i); i++}}' /etc/grub2.cfg
linux16 7
/vmlinuz-3.10.0-862.14.4.el7.x86_64 35
root=UUID=17c90f0e-0bf0-40ea-8a5e-9598aa668053 46
ro 2
crashkernel=auto 16
rhgb 4
quiet 5
LANG=zh_CN.UTF-8 16
linux16 7
/vmlinuz-3.10.0-862.el7.x86_64 30
root=UUID=17c90f0e-0bf0-40ea-8a5e-9598aa668053 46
ro 2
crashkernel=auto 16
rhgb 4
quiet 5
LANG=zh_CN.UTF-8 16
linux16 7
/vmlinuz-0-rescue-d5bf70a4141c42668b79f9b042c2b21e 50
root=UUID=17c90f0e-0bf0-40ea-8a5e-9598aa668053 46
ro 2
crashkernel=auto 16
rhgb 4
quiet 5
do statement while(condition):类似while,但至少执行一次循环体.
语法:do statement while(condition)
[root@zcy520ooooo ~]# awk '/^[[:space:]]*save/{i=1;do {if(length($i)>10) {print $i,length($i)}; i++} while(i<=NF)}' /etc/grub2.cfg
saved_entry 11
prev_saved_entry 16
saved_entry="${chosen}" 23
saved_entry 11
for循环:循环或遍历数组中的元素
语法：for(expr1;expr2;expr3) statement
for(var in array) {for-body} 遍历数组中的元素
[root@zcy520ooooo ~]# awk '/^[[:space:]]*linux16/{for(i=1;i<=NF;i++) {print $i,length($i)}}' /etc/grub2.cfg
linux16 7
/vmlinuz-3.10.0-862.14.4.el7.x86_64 35
root=UUID=17c90f0e-0bf0-40ea-8a5e-9598aa668053 46
ro 2
crashkernel=auto 16
rhgb 4
quiet 5
LANG=zh_CN.UTF-8 16
linux16 7
/vmlinuz-3.10.0-862.el7.x86_64 30
root=UUID=17c90f0e-0bf0-40ea-8a5e-9598aa668053 46
ro 2
crashkernel=auto 16
rhgb 4
quiet 5
LANG=zh_CN.UTF-8 16
linux16 7
/vmlinuz-0-rescue-d5bf70a4141c42668b79f9b042c2b21e 50
root=UUID=17c90f0e-0bf0-40ea-8a5e-9598aa668053 46
ro 2
crashkernel=auto 16
rhgb 4
quiet 5
switch语句:控制开关语句,匹配到的字段符合某项进行处理
语法:switch(expression) {case VALUE1 or /REGEXP/: statement; case VALUE2 or /REGEXP2/: statement; ...; default: statement}
在if,while等控制语句中也可以使用中断,退出等.
break[n]:退出循环,在n退出循环
continue:结束当前循环并跳转到循环开始处
exit:返回状态码并退出循环
next:awk的特殊语句,提前结束对本行的处理而直接进入下一行
[root@zcy520ooooo ~]# awk -F: '{if($3%2!=1) next; print $1,$2,$3}' /etc/passwd
bin x 1
adm x 3
sync x 5
halt x 7
operator x 11
nobody x 99
dbus x 81
polkitd x 999
postfix x 89
tss x 59
geoclue x 997
logstash x 1011
gluster x 995
libstoragemgmt x 993
usbmuxd x 113
qemu x 107
radvd x 75
abrt x 173
colord x 991
pulse x 171
rpcuser x 29
gnome-initial-setup x 989
8. 关联数组:array[index-expression]
awk支持关联数组(自定义的数组)
index-expression:
(1) 可使用任意字符串；字符串要使用双引号；
(2) 如果某数组元素事先不存在，在引用时，awk会自动创建此元素，并将其值初始化为“空串”
若要判断数组中是否存在某元素，要使用"index in array"格式进行;
若要遍历数组中的每个元素，要使用for循环:
for(var in array) {for-body}
[root@zcy520ooooo ~]# awk 'BEGIN{DAY["a"]="10.1";DAY["b"]="10.2";for(i in DAY) {print DAY[i]}}'
10.1
10.2
# 注意这里的i在后面输出是不用双引号或者$符号修饰,直接引用i就可以
注意var会遍历array的每个索引; state["a"]++表示数组索引的值进行自增DAY["a"]=3,DAY[a]++表示3自增
[root@zcy520ooooo ~]# awk '{installed[$5]++}END{for(i in installed) {print i,installed[i]}}' /var/log/yum.log
GConf2-3.2.6-8.el7.x86_64 1
gnome-color-manager-3.22.2-2.el7.x86_64 1
nss-3.36.0-7.el7_5.x86_64 1
gnome-shell-extension-apps-menu-3.26.2-3.el7.noarch 1
sane-backends-1.0.24-11.el7.x86_64 1
1:NetworkManager-libnm-1.10.2-16.el7_5.x86_64 1
colord-libs-1.3.4-1.el7.x86_64 1
unzip-6.0-19.el7.x86_64 1
cdparanoia-libs-10.2-17.el7.x86_64 1
xcb-util-wm-0.4.1-5.el7.x86_64 1
uom-se-1.0.4-3.el7.noarch 1
spice-gtk3-0.34-3.el7_5.2.x86_64 1
1:perl-Log-Message-0.08-3.el7.noarch 1
fontconfig-2.10.95-11.el7.x86_64 1
gcc-gfortran-4.8.5-28.el7_5.1.x86_64 1
httpd-2.4.6-80.el7.centos.1.x86_64 1
dejavu-sans-fonts-2.33-6.el7.noarch 1
freerdp-libs-1.0.2-15.el7.x86_64 1
1:librados2-0.94.5-2.el7.x86_64 1
python-enum34-1.0.4-1.el7.noarch 1
xdg-user-dirs-gtk-0.10-4.el7.x86_64 1
libreport-plugin-ureport-2.1.11-40.el7.centos.x86_64 1
libref_array-0.1.5-29.el7.x86_64 1
gnome-themes-standard-3.22.2-2.el7_5.x86_64 1
lsof-4.87-5.el7.x86_64 1
perl-Pod-Usage-1.63-3.el7.noarch 1
marisa-0.2.4-4.el7.x86_64 1
libvirt-python-3.9.0-1.el7.x86_64 1
libxml2-python-2.9.1-6.el7_2.3.x86_64 1
libwvstreams-4.6.1-11.el7.x86_64 1
scrub-2.5.2-7.el7.x86_64 1
perl-Exporter-5.68-3.el7.noarch 1
colord-1.3.4-1.el7.x86_64 1
perl-Module-Metadata-1.000018-2.el7.noarch 1
lohit-marathi-fonts-2.5.3-2.el7.noarch 1
jsr-311-1.1.1-6.el7.noarch 1
osinfo-db-20170813-6.el7.noarch 1
plymouth-plugin-label-0.8.9-0.31.20140113.el7.centos.x86_64 1
libsoup-2.56.0-6.el7.x86_64 1
qgnomeplatform-0.3-3.el7.x86_64 1
netcf-libs-0.2.8-4.el7.x86_64 1
xorg-x11-xinit-1.3.4-2.el7.x86_64 1
rarian-0.8.1-11.el7.x86_64 1
perl-Scalar-List-Utils-1.27-248.el7.x86_64 1
flatpak-libs-0.8.8-4.el7_5.x86_64 1
evolution-mapi-3.22.6-1.el7.x86_64 1
javassist-3.16.1-10.el7.noarch 1
sssd-ad-1.16.0-19.el7_5.8.x86_64 1
libvirt-client-3.9.0-14.el7_5.8.x86_64 1
firstboot-19.12-1.el7.x86_64 1
1:isomd5sum-1.0.10-5.el7.x86_64 1
libreport-plugin-mantisbt-2.1.11-40.el7.centos.x86_64 1
1:xorg-x11-xauth-1.0.9-1.el7.x86_64 1
xvattr-1.3-27.el7.x86_64 1
grilo-0.3.3-1.el7.x86_64 1
libraw1394-2.1.0-2.el7.x86_64 1
libdhash-0.5.0-29.el7.x86_64 1
lyx-fonts-2.2.3-1.el7.noarch 1
objectweb-asm-3.3.1-9.el7.noarch 1
mpfr-3.1.1-4.el7.x86_64 1
sil-nuosu-fonts-2.1.1-5.el7.noarch 1
pulseaudio-gdm-hooks-10.0-5.el7.x86_64 1
libchamplain-gtk-0.12.15-1.el7.x86_64 1
totem-pl-parser-3.10.7-1.el7.x86_64 1
libchamplain-0.12.15-1.el7.x86_64 1
libsss_autofs-1.16.0-19.el7_5.8.x86_64 1
abrt-libs-2.1.11-50.el7.centos.x86_64 1
plymouth-theme-charge-0.8.9-0.31.20140113.el7.centos.x86_64 1
librsvg2-2.40.16-1.el7.x86_64 1
libsmbclient-4.7.1-9.el7_5.x86_64 1
...#以下省略
描述awk函数示例(至少3例)
awk支持的内置函数主要有3种:算数函数、字符串函数、其他一般函数、时间函数;常用的内置函数如下：
内置函数
数值处理：
rand()：返回0和1之间一个随机数；
字符串处理：
length([s])：返回指定字符串的长度；
sub(r,s,[t])：以r表示的模式来查找t所表示的字符中的匹配的内容，并将其第一次出现替换为s所表示的内容；
gsub(r,s,[t])：以r表示的模式来查找t所表示的字符中的匹配的内容，并将其所有出现均替换为s所表示的内容；
split(s,a[,r])：以r为分隔符切割字符s，并将切割后的结果保存至a所表示的数组中
[root@zcy520ooooo ~]# awk '{for(i=1;i<length(NF);i++) print $1}' /etc/passwd
tss:x:59:59:Account
[root@zcy520ooooo ~]# awk 'BEGIN{rd=int(100*rand());print rd}'
23
[root@zcy520ooooo ~]# awk 'BEGIN{haha="ab cd e f gg ha2 1 23 4 5a SD F V df?";split(haha,line," ");print length(line);for(i in line){print i,line[i]}}'
14
4 f
5 gg
6 ha2
7 1
8 23
9 4
10 5a
11 SD
12 F
13 V
14 df?
1 ab
2 cd
3 e
