Awk常用记录

awk 'BEGIN{ commands } pattern{ commands } END{ commands }'

$ echo -e "A line 1\nA line 2" | awk 'BEGIN{ print "Start" } { print } END{ print "End" }'

Start
A line 1
A line 2
End

统计文件中的行数：
 awk 'END{ print NR }' filename 
 
以上命令只使用了END语句块，在读入每一行的时，awk会将NR更新为对应的行号，当到达最后一行NR的值就是最后一行的行号，所以END语句块中的NR就是文件的行数。

1 hello, world
2 this is a test
3 Are you like awk
This's a test
10 There are orange,apple,mongo

$awk '{print $1}' log.txt
1
2
3
this's
10

awk -F, '{print $1}' log.txt
1 hello
2 this is a test
3 Are you like awk
this's  a test
10 There are orange

============或者使用内建变量=================

$ awk 'BEGIN{FS=","} {print $1,$2}'     log.txt
1 hello  world
2 this is a test
3 Are you like awk
this's  a test
10 There are orange apple

$ awk -v a=1 '{print $1,$1+a}' log.txt
1 2
2 3
3 4
this's 1
10 11

$ awk -f cal.awk log.txt

awk '$1>2' log.txt
3 Are you like awk
this's  a test
10 There are orange,apple,mongo

$ awk '{print NR,FNR,$1,$2,$3}' log.txt
1 1 2 this is
2 2 3 Are you
3 3 This's a test
4 4 10 There are

# 指定输出分割符
$  awk '{print $1,$2,$5}' OFS=" $ "  log.txt
2 $ this $ test
3 $ Are $ awk
This's $ a $
10 $ There $

# 输出第二列包含 "th"，并打印第二列与第四列
$ awk '$2 ~ /th/ {print $2,$4}' log.txt
this a

~ 表示模式开始。// 中是模式。
# 输出包含"re" 的行
$ awk '/re/ ' log.txt
---------------------------------------------
3 Are you like awk
10 There are orange,apple,mongo

$ awk 'BEGIN{IGNORECASE=1} /this/' log.txt
---------------------------------------------
2 this is a test
This's a test

$ awk '$2 !~ /th/ {print $2,$4}' log.txt
---------------------------------------------
Are like
a
There orange,apple,mongo
$ awk '!/th/ {print $2,$4}' log.txt
---------------------------------------------
Are like
a
There orange,apple,mongo

关于awk脚本，我们需要注意两个关键词BEGIN和END。
BEGIN{ 这里面放的是执行前的语句 }
END {这里面放的是处理完所有的行后要执行的语句 }
{这里面放的是处理每一行时要执行的语句}

$ cat score.txt
Marry   2143 78 84 77
Jack    2321 66 78 45
Tom     2122 48 77 71
Mike    2537 87 97 95
Bob     2415 40 57 62

$ cat cal.awk
#!/bin/awk -f
#运行前
BEGIN {
    math = 0
    english = 0
    computer = 0
 
    printf "NAME    NO.   MATH  ENGLISH  COMPUTER   TOTAL\n"
    printf "---------------------------------------------\n"
}
#运行中
{
    math+=$3
    english+=$4
    computer+=$5
    printf "%-6s %-6s %4d %8d %8d %8d\n", $1, $2, $3,$4,$5, $3+$4+$5
}
#运行后
END {
    printf "---------------------------------------------\n"
    printf "  TOTAL:%10d %8d %8d \n", math, english, computer
    printf "AVERAGE:%10.2f %8.2f %8.2f\n", math/NR, english/NR, computer/NR
}

$ awk -f cal.awk score.txt
NAME    NO.   MATH  ENGLISH  COMPUTER   TOTAL
---------------------------------------------
Marry  2143     78       84       77      239
Jack   2321     66       78       45      189
Tom    2122     48       77       71      196
Mike   2537     87       97       95      279
Bob    2415     40       57       62      159
---------------------------------------------
  TOTAL:       319      393      350
AVERAGE:     63.80    78.60    70.00