awk

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awk是一个强大的文本分析工具，awk工作原理：把文件逐行的读入，以空格为默认分隔符将每行切片，切开的部分再进行各种分析处理。

来源

awk是因为其取了三位创始人 Alfred Aho，Peter Weinberger, 和 Brian Kernighan 的 Family Name 的首字符。

awk有3个不同版本: awk、nawk和gawk，未作特别说明，一般指gawk，gawk 是 awk 的 GNU 版本。

安装

yum install -y gawk

Help

# awk --help
Usage: awk [POSIX or GNU style options] -f progfile [--] file ...
Usage: awk [POSIX or GNU style options] [--] 'program' file ...
POSIX options:		GNU long options: (standard)
	-f progfile		--file=progfile
	-F fs			--field-separator=fs
	-v var=val		--assign=var=val
Short options:		GNU long options: (extensions)
	-b			--characters-as-bytes
	-c			--traditional
	-C			--copyright
	-d[file]		--dump-variables[=file]
	-e 'program-text'	--source='program-text'
	-E file			--exec=file
	-g			--gen-pot
	-h			--help
	-L [fatal]		--lint[=fatal]
	-n			--non-decimal-data
	-N			--use-lc-numeric
	-O			--optimize
	-p[file]		--profile[=file]
	-P			--posix
	-r			--re-interval
	-S			--sandbox
	-t			--lint-old
	-V			--version

To report bugs, see node `Bugs' in `gawk.info', which is
section `Reporting Problems and Bugs' in the printed version.

gawk is a pattern scanning and processing language.
By default it reads standard input and writes standard output.

Examples:
	gawk '{ sum += $1 }; END { print sum }' file
	gawk -F: '{ print $1 }' /etc/passwd

内建变量

  • $0 当前记录（这个变量中存放着整个行的内容）
  • $1~$n 前记录的第n个字段，字段间由FS分隔
  • FS 输入字段分隔符 默认是空格或Tab
  • NF 当前记录中的字段个数，就是有多少列
  • NR 已经读出的记录数，就是行号，从1开始，如果有多个文件话，这个值也是不断累加中。
  • FNR 当前记录数，与NR不同的是，这个值会是各个文件自己的行号
  • RS 输入的记录分隔符， 默认为换行符
  • OFS 输出字段分隔符， 默认也是空格
  • ORS 输出的记录分隔符，默认为换行符
  • FILENAME 当前输入文件的名字

示例

# cat netstat.txt
Proto Recv-Q Send-Q Local Address           Foreign Address         State
tcp        0      0 a1.xiexianbin.cn:55536  100.100.15.4:https      TIME_WAIT
tcp        0     36 a1.xiexianbin.cn:ssh    101.226.164.165:53138   ESTABLISHED
tcp        0      0 localhost:36654         localhost:2379          ESTABLISHED
tcp        0      0 localhost:2379          localhost:36654         ESTABLISHED
tcp        0      0 localhost:59236         localhost:2379          ESTABLISHED
tcp        0      0 localhost:2379          localhost:59238         ESTABLISHED
tcp        0      0 localhost:59238         localhost:2379          ESTABLISHED

基本用法

# awk '{print $1, $4}' netstat.txt
Proto Local
tcp a1.xiexianbin.cn:55536
tcp a1.xiexianbin.cn:ssh
tcp localhost:36654
tcp localhost:2379
tcp localhost:59236
tcp localhost:2379
tcp localhost:59238
  • 单引号中的被大括号括着的就是awk的语句
  • 其只能被单引号包含

格式化输出

# awk '{printf "%-8s %-8s %-8s %-18s %-22s %-15s\n",$1,$2,$3,$4,$5,$6}' netstat.txt
Proto    Recv-Q   Send-Q   Local              Address                Foreign
tcp      0        0        a1.xiexianbin.cn:55536 100.100.15.4:https     TIME_WAIT
tcp      0        36       a1.xiexianbin.cn:ssh 101.226.164.165:53138  ESTABLISHED
tcp      0        0        localhost:36654    localhost:2379         ESTABLISHED
tcp      0        0        localhost:2379     localhost:36654        ESTABLISHED
tcp      0        0        localhost:59236    localhost:2379         ESTABLISHED
tcp      0        0        localhost:2379     localhost:59238        ESTABLISHED
tcp      0        0        localhost:59238    localhost:2379         ESTABLISHED
  • awk的格式化输出，和C语言的printf

过滤

# awk '$3==0 && $6=="ESTABLISHED" ' netstat.txt    # 第三列的值为0 && 第6列的值为ESTABLISHED
tcp        0      0 localhost:36654         localhost:2379          ESTABLISHED
tcp        0      0 localhost:2379          localhost:36654         ESTABLISHED
tcp        0      0 localhost:59236         localhost:2379          ESTABLISHED
tcp        0      0 localhost:2379          localhost:59238         ESTABLISHED
tcp        0      0 localhost:59238         localhost:2379          ESTABLISHED
# awk ' $3>0 {print $0}' netstat.txt    # 第三列的值大于0
Proto Recv-Q Send-Q Local Address           Foreign Address         State
tcp        0     36 a1.xiexianbin.cn:ssh    101.226.164.165:53138   ESTABLISHED
# awk '$3==0 && $6=="ESTABLISHED" || NR==1 ' netstat.txt
Proto Recv-Q Send-Q Local Address           Foreign Address         State
tcp        0      0 localhost:36654         localhost:2379          ESTABLISHED
tcp        0      0 localhost:2379          localhost:36654         ESTABLISHED
tcp        0      0 localhost:59236         localhost:2379          ESTABLISHED
tcp        0      0 localhost:2379          localhost:59238         ESTABLISHED
tcp        0      0 localhost:59238         localhost:2379          ESTABLISHED
# awk '$3==0 && $6=="ESTABLISHED" || NR==1 {printf "%-20s %-20s %s\n",$4,$5,$6}' netstat.txt
Local                Address              Foreign
localhost:36654      localhost:2379       ESTABLISHED
localhost:2379       localhost:36654      ESTABLISHED
localhost:59236      localhost:2379       ESTABLISHED
localhost:2379       localhost:59238      ESTABLISHED
localhost:59238      localhost:2379       ESTABLISHED
# awk  'BEGIN{FS=":"} {print $1,$3,$6}' /etc/passwd
root 0 /root
bin 1 /bin
daemon 2 /sbin
# awk  -F: '{print $1,$3,$6}' /etc/passwd
root 0 /root
bin 1 /bin
daemon 2 /sbin
# awk  -F: '{print $1,$3,$6}' OFS="\t" /etc/passwd
root	0	/root
bin	1	/bin
daemon	2	/sbin
# awk '$6 ~ /FIN|TIME/ || NR==1 {print NR,$4,$5,$6}' OFS="\t" netstat.txt
1	Local	Address	Foreign
2	a1.xiexianbin.cn:55536	100.100.15.4:https	TIME_WAIT
# awk '/TIME_WAIT/' netstat.txt
tcp        0      0 a1.xiexianbin.cn:55536  100.100.15.4:https      TIME_WAIT
# awk '$6 !~ /WAIT/ || NR==1 {print NR,$4,$5,$6}' OFS="\t" netstat.txt
1	Local	Address	Foreign
3	a1.xiexianbin.cn:ssh	101.226.164.165:53138	ESTABLISHED
4	localhost:36654	localhost:2379	ESTABLISHED
5	localhost:2379	localhost:36654	ESTABLISHED
6	localhost:59236	localhost:2379	ESTABLISHED
7	localhost:2379	localhost:59238	ESTABLISHED
8	localhost:59238	localhost:2379	ESTABLISHED
# awk '!/WAIT/' netstat.txt
Proto Recv-Q Send-Q Local Address           Foreign Address         State
tcp        0     36 a1.xiexianbin.cn:ssh    101.226.164.165:53138   ESTABLISHED
tcp        0      0 localhost:36654         localhost:2379          ESTABLISHED
tcp        0      0 localhost:2379          localhost:36654         ESTABLISHED
tcp        0      0 localhost:59236         localhost:2379          ESTABLISHED
tcp        0      0 localhost:2379          localhost:59238         ESTABLISHED
tcp        0      0 localhost:59238         localhost:2379          ESTABLISHED
  • 比较运算符：==, !=, >, <, >=, <=
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