AWK之随心所欲-基础篇

一、简介

awk 是一个处理文本的编程语言工具，能用简短的程序处理标准输入或文件、数据排序、计算以及 生成报表等等。

在 Linux 系统下默认 awk 是 gawk，它是 awk 的 GNU 版本。可以通过命令查看应用的版本：ls -l /bin/awk

基本的命令语法： awk option 'pattern {action}' file

其中 pattern 表示 AWK 在数据中查找的内容，而 action 是在找到匹配内容时所执行的一系列命令。 花括号用于根据特定的模式对一系列指令进行分组。

awk 处理的工作方式与数据库类似，支持对记录和字段处理，这也是 grep 和 sed 不能实现的。 在 awk 中，缺省的情况下将文本文件中的一行视为一个记录，逐行放到内存中处理，而将一行中的 某一部分作为记录中的一个字段。用 1,2,3...数字的方式顺序的表示行（记录）中的不同字段。用 $后跟数字，引用对应的字段，以逗号分隔，0 表示整个行。

二、OPTION

选项描述

选项	描述
-f	从文件中读取 awk 程序源文件
-F	指定 fs 为输入字段分隔符
-v	var=value 变量赋值
--posix	兼容 POSIX 正则表达式
--dump-variables=[file]	把 awk 命令时的全局变量写入文件， 默认文件是 awkvars.out

三、pattern

模式描述

模式	描述
BEGIN{ }	给程序赋予初始状态，先执行的工作
END{ }	程序结束之后执行的一些扫尾工作
/regular expression/	为每个输入记录匹配正则表达式
pattern && pattern	逻辑 and，满足两个模式
pattern1, pattern2	范围模式，匹配所有模式 1 的记录，直到匹配到模式 2
action	就是print、流程控制。I/O语句

四、案例

1.从文件读取awk的程序

[root@localhost ~]# cat test.awk
{print $2}
[root@localhost ~]# tail -n3 /etc/services |awk -f test.awk
48619/tcp
48619/udp
49000/tcp

2.变量赋值

[root@192 ~]# awk -v a=1 'BEGIN{print a}'
1
[root@192 ~]# a=3
[root@192 ~]# awk -v a=$a 'BEGIN{print a}'
3

[root@192 ~]# awk 'BEGIN{print '$a'}'  单引号调用变量
3

3.全局变量到文件

[root@localhost ~]# seq 5|awk --dump-variables '{print $0}'
1
2
3
4
5

[root@localhost ~]# cat awkvars.out  默认文件
ARGC: 1
ARGIND: 0
ARGV: array, 1 elements
BINMODE: 0
CONVFMT: "%.6g"
ERRNO: ""
FIELDWIDTHS: ""
FILENAME: "-"
FNR: 5
FPAT: "[^[:space:]]+"
FS: " "
IGNORECASE: 0
LINT: 0
NF: 1
NR: 5
OFMT: "%.6g"
OFS: " "
ORS: "\n"
RLENGTH: 0
RS: "\n"
RSTART: 0
RT: "\n"
SUBSEP: "\034"
TEXTDOMAIN: "messages"

4.BEGIN 处理文件前的操作，修改内置变量 变量赋值 页眉和标题

[root@192 ~]# tail /etc/services |awk 'BEGIN{print "Service\t\tTport\t\t\tDescription"}{print $0}'
Service         Tport                   Description
3gpp-cbsp       48049/tcp               # 3GPP Cell Broadcast Service Protocol
isnetserv       48128/tcp               # Image Systems Network Services
isnetserv       48128/udp               # Image Systems Network Services
blp5            48129/tcp               # Bloomberg locator
blp5            48129/udp               # Bloomberg locator
com-bardac-dw   48556/tcp               # com-bardac-dw
com-bardac-dw   48556/udp               # com-bardac-dw
iqobject        48619/tcp               # iqobject
iqobject        48619/udp               # iqobject
matahari        49000/tcp               # Matahari Broker

5.END 程序执行完了 才会执行后面的END的动作

[root@192 ~]# tail /etc/services |awk '{print $0}END{print "====\nEND"}'
3gpp-cbsp       48049/tcp               # 3GPP Cell Broadcast Service Protocol
isnetserv       48128/tcp               # Image Systems Network Services
isnetserv       48128/udp               # Image Systems Network Services
blp5            48129/tcp               # Bloomberg locator
blp5            48129/udp               # Bloomberg locator
com-bardac-dw   48556/tcp               # com-bardac-dw
com-bardac-dw   48556/udp               # com-bardac-dw
iqobject        48619/tcp               # iqobject
iqobject        48619/udp               # iqobject
matahari        49000/tcp               # Matahari Broker
====
END

6. --profile 输出命令到文件

[root@192 ~]# tail /etc/services |awk --profile 'BEGIN{print "service\t\ttport\t\t\tde\n=="}{print $0}END{print"====\nEND...."}'
service         tport                   de
==
3gpp-cbsp       48049/tcp               # 3GPP Cell Broadcast Service Protocol
isnetserv       48128/tcp               # Image Systems Network Services
isnetserv       48128/udp               # Image Systems Network Services
blp5            48129/tcp               # Bloomberg locator
blp5            48129/udp               # Bloomberg locator
com-bardac-dw   48556/tcp               # com-bardac-dw
com-bardac-dw   48556/udp               # com-bardac-dw
iqobject        48619/tcp               # iqobject
iqobject        48619/udp               # iqobject
matahari        49000/tcp               # Matahari Broker
====
END....

[root@localhost ~]# cat awkprof.out
# gawk profile, created Mon Jul 22 17:13:27 2019

# BEGIN block(s)

BEGIN {
print "service\t\ttport\t\t\tde\n=="
}

# Rule(s)

{
print $0
}

# END block(s)

END {
print "====\nEND...."
}

7./re/ 正则匹配

匹配第一个字段是8个字符行的
[root@192 ~]# tail /etc/services |awk '/^[a-z0-9]{8}/{print $0}'
isnetserv       48128/tcp               # Image Systems Network Services
isnetserv       48128/udp               # Image Systems Network Services
iqobject        48619/tcp               # iqobject
iqobject        48619/udp               # iqobject
matahari        49000/tcp               # Matahari Broker

匹配tcp字段的行
[root@192 ~]# tail /etc/services |awk '/tcp/{print $0}'
3gpp-cbsp       48049/tcp               # 3GPP Cell Broadcast Service Protocol
isnetserv       48128/tcp               # Image Systems Network Services
blp5            48129/tcp               # Bloomberg locator
com-bardac-dw   48556/tcp               # com-bardac-dw
iqobject        48619/tcp               # iqobject
matahari        49000/tcp               # Matahari Broker

匹配已blp5开头的行
[root@192 ~]# tail /etc/services |awk '/^blp5/{print $0}'
blp5            48129/tcp               # Bloomberg locator
blp5            48129/udp               # Bloomberg locator

8. 逻辑and or not

匹配blp5和tcp的行
[root@192 ~]# tail /etc/services |awk '/blp5/ && /tcp/{print $0}'
blp5            48129/tcp               # Bloomberg locator

匹配blp5或tcp的行
[root@192 ~]# tail /etc/services |awk '/blp5/ | /tcp/{print $0}'
3gpp-cbsp       48049/tcp               # 3GPP Cell Broadcast Service Protocol
isnetserv       48128/tcp               # Image Systems Network Services
blp5            48129/tcp               # Bloomberg locator
blp5            48129/udp               # Bloomberg locator
com-bardac-dw   48556/tcp               # com-bardac-dw
iqobject        48619/tcp               # iqobject
matahari        49000/tcp               # Matahari Broker
或
[root@192 ~]#  tail /etc/services |awk '/blp5|tcp/{print $0}'
3gpp-cbsp       48049/tcp               # 3GPP Cell Broadcast Service Protocol
isnetserv       48128/tcp               # Image Systems Network Services
blp5            48129/tcp               # Bloomberg locator
blp5            48129/udp               # Bloomberg locator
com-bardac-dw   48556/tcp               # com-bardac-dw
iqobject        48619/tcp               # iqobject
matahari        49000/tcp               # Matahari Broker

不匹配#开头和空行
[root@192 ~]# cat test.txt|awk '!/^#/ && !/^$/{print $0}'
dadadad
111111
[root@192 ~]# cat test.txt
#dasdsdadad

dadadad
111111
#vvvvv
或
[root@192 ~]# cat test.txt  |awk '/^[^#]|"^$"/'      _待解释_
dadadad
111111

9.匹配范围

开始匹配第一个关键字，到匹配第二个关键字结束
[root@192 ~]# tail /etc/services |awk '/^3gp/,/^com/{print $0}'
3gpp-cbsp       48049/tcp               # 3GPP Cell Broadcast Service Protocol
isnetserv       48128/tcp               # Image Systems Network Services
isnetserv       48128/udp               # Image Systems Network Services
blp5            48129/tcp               # Bloomberg locator
blp5            48129/udp               # Bloomberg locator
com-bardac-dw   48556/tcp               # com-bardac-dw