awk学习笔记

#vi employees

Tom Jones    4424    5/12/66    553354

Mary Adams   5346    11/4/63    28765

Sally Chang  1654    7/22/54    650000

Billy Black  1683    9/23/44    336500

 

#sed 's/\t/:/g' employees > employees2

 

#more employees2

Tom Jones:4424:5/12/66:553354

Mary Adams:5346:11/4/63:28765

Sally Chang:1654:7/22/54:650000

Billy Black:1683:9/23/44:336500

 

#awk -F: 'Tom Jones/{print $1,$2}' employees2

Tom Jones   4424

 

#awk -F'[ :\t] 'Tom Jones/{print $1,$2,$3}' employees2

Tom Jones    4424

Mary Adams   5346

Sally Chang  1654

Billy Black  1683    

 

#awk -F: '/Tom Jones/{print $1,$2,$3,$4}' employees2
Tom JOnes 4424 5/12/66 543354

#awk -F: '/Tom Jones/{print $0}' employees2
Tom Jones:4424:5/12/66:543354

#awk '/Tom Jones/{print $0}' employees2
Tom Jones:4424:5/12/66:543354

 

模式与操作

1）模式

awk模式用来控制awk对输入的文本行执行什么操作。操作由正则表达式，判别条件真伪的表达式或两者的组合构成。awk的默认操作是打印所有使表达式结果为真的文本行。

注意：模式表达式中暗含着if语句。如果模式表达式含有if的意思，就不必用花括号把它括起来。当if是显式

     的给出时，这个表达式就成了操作语句。语法将不同。

 

#cat employees

Tom Jones    4424    5/12/66    553354

Mary Adams   5346    11/4/63    28765

Sally Chang  1654    7/22/54    650000

Billy Black  1683    9/23/44    336500

 

#awk '/Tom/' employees

Tom Jones    4424    5/12/66    543354

注：如果输入文件中匹配到模式Tom，则打印Tom所在的记录。如果没有显式的指定操作，默认操作是打印文本

   行，等价于命令

   awk '$0 ~ /Tom/{print $0}' employees

   而awk '$0 !~ /Tom/{print $0}' employees

   则打印除Tom Jones以外的其他记录

   Mary Adams   5346    11/4/63    28765

   Sally Chang  1654    7/22/54    650000

   Billy Black  1683    9/23/44    336500

 

#awk '$3<4000' employees

Sally Chang  1654    7/22/54    650000

Billy Black  1683    9/23/44    336500

注：如果第3个字段的值小于4000，则打印该记录

 

2）操作

操作是以{}分隔的语句。如果操作前面有个模式，则模式控制着操作的范围。同一行内的多条语句由分号分隔，独占一行的语句则以换行符分隔

 

模式{操作语句；操作语句；。。。}

或

模式{

操作语句

操作语句

}

注：操作如果紧跟在某个模式后面，它的第一个左花括号就必须与该模式同处一行。模式永远不会出现在花括

   号中。

 

#awk ’/Tom/{print "Hello there, " $1}' employees

Hello there,Tom

注：如果没有为模式指定操作，就会打印所有匹配该模式的文本行。

 

# awk '/^Mary/' employees                    
Mary Adama      5346    11/4/63 28765

 

# awk '/^[A-Z][a-z]+ /' employees
Tom Jones       4424    5/12/66 543354
Mary Adama      5346    11/4/63 28765
Sally chang     1654    7/22/54 650000
Billy Black     1683    9/23/44 336500

 

匹配操作符(~)用于对记录或字段的表达式进行匹配
# cat employees
Tom Jones       4424    5/12/66 543354
Mary Adama      5346    11/4/63 28765
Sally chang     1654    7/22/54 650000
Billy Black     1683    9/23/44 336500

# awk '$1 ~ /[Bb]ill/' employees
Billy Black     1683    9/23/44 336500

# awk '$1 !~ /ly$/' employees      
Tom Jones       4424    5/12/66 543354
Mary Adama      5346    11/4/63 28765

# more employees2
Tom Jones:4424:5/12/66:543354
Mary Adama:5346:11/4/63:28765
Sally chang:1654:7/22/54:650000
Billy Black:1683:9/23/44:336500

# more info
/Tom/{print "Tom's birthday is" $3}
/Mary/{print NR,$0}
/^Sally/{print "Hi Sally." $1 "has a salary of $"$4 "."}

# cat info
/Tom/{print "Tom's birthday is" $3}
/Mary/{print NR,$0}
/^Sally/{print "Hi Sally." $1 "has a salary of $"$4 "."}

# awk -F: -f info employees2
Tom's birthday is5/12/66
2 Mary Adama:5346:11/4/63:28765
Hi Sally.Sally changhas a salary of $650000.

复习
# awk '/west/' datafile
northwest       NW      Charles Main    3.0     .98     3       34
western         WE      Sharon Gray     5.3     .97     5       23
southwest       SW      Lewis Dalsass   2.7     .8      2       18

# awk '/^north/' datafile
northwest       NW      Charles Main    3.0     .98     3       34
northeast       NE      AM Main Jr.     5.1     .94     3       13
north           NO      Margot Weber    4.5     .89     5       9

# awk '/^(no|so)/' datafile
northwest       NW      Charles Main    3.0     .98     3       34
southwest       SW      Lewis Dalsass   2.7     .8      2       18
southern        SO      Suan Chin       5.1     .95     4       15
southeast       SE      Patricia Hemenway       4.0     .7      4       17
northeast       NE      AM Main Jr.     5.1     .94     3       13
north           NO      Margot Weber    4.5     .89     5       9

# awk '{print $3,$2}' datafile
Charles NW
Sharon WE
 
Lewis SW
Suan SO
Patricia SE
TB EA
AM NE
Margot NO
Ann CT

# awk 'print S1' datafile
 syntax error The source line is 1.
 The error context is
                 >>> print <<<  S1
 awk: Quitting
 The source line is 1.

# awk '{print $1}' datafile  
northwest
western
southwest
southern
southeast
eastern
northeast
north
central

# awk '{print $0}' datafile
northwest       NW      Charles Main    3.0     .98     3       34
western         WE      Sharon Gray     5.3     .97     5       23

southwest       SW      Lewis Dalsass   2.7     .8      2       18
southern        SO      Suan Chin       5.1     .95     4       15
southeast       SE      Patricia Hemenway       4.0     .7      4       17
eastern         EA      TB Savage       4.4     .84     5       20
northeast       NE      AM Main Jr.     5.1     .94     3       13
north           NO      Margot Weber    4.5     .89     5       9
central         CT      Ann Stephens    5.7     .94     5       13

# awk '{print "Number of fields: " NF}' datafile
Number of fields: 8
Number of fields: 8
Number of fields: 0
Number of fields: 8
Number of fields: 8
Number of fields: 8
Number of fields: 8
Number of fields: 9
Number of fields: 8
Number of fields: 8
Number of fields: 0

# awk '/northeast/{print $3,$2}' datafile
AM NE

# awk '/E/' datafile
western         WE      Sharon Gray     5.3     .97     5       23
southeast       SE      Patricia Hemenway       4.0     .7      4       17
eastern         EA      TB Savage       4.4     .84     5       20
northeast       NE      AM Main Jr.     5.1     .94     3       13

# awk '/^[ns]/{print $1}' datafile
northwest
southwest
southern
southeast
northeast
north

# awk '$5 ~/\.[7-9]+/' datafile
southwest       SW      Lewis Dalsass   2.7     .8      2       18
central         CT      Ann Stephens    5.7     .94     5       13

# awk '$2 !~ /E/{print $1,$2}' datafile
northwest NW
 
southwest SW
southern SO
north NO
central CT

# awk '$3 ~/^Suan/{print $3 "is a nice girl."}' datafile
Suanis a nice girl.

# awk '$8 ~ /[0-9][0-9]$/{print $8}' datafile
34
23
18
15
17
20
13

# awk '$4 ~ /Chin$/{printf "The price is $" $8 ".\n"}' datafile
The price is $15.

# awk '/NO/{print $0}' datafile
north           NO      Margot Weber    4.5     .89     5       9

# cp datafile datafile.test
# vi datafile.test
"datafile.test" 11 lines, 346 characters
northwest       NW      Charles Main    3.0     .98     3       34
western         WE      Sharon Gray     5.3     .97     5       23

southwest       SW      Lewis Dalsass   2.7     .8      2       18
southern        SO      Suan Chin       5.1     .95     4       15
southeast       SE      Patricia Hemenway       4.0     .7      4       17
eastern         EA      TB Savage       4.4     .84     5       20
northeast       NE      AM Main Jr.     5.1     .94     3       13
north           NO      Margot Weber    4.5     .89     5       9
central         CT      Ann Stephens    5.7     .94     5       13
通过vi修改此文件，获得所需要表现形式
当前字段之间是制表符(除$3,$4之间为空格)，利用vi的：1,$s/\t/:/g替换

# cat datafile.test
northwest:NW:Charles Main:3.0:.98:3:34
western:WE:Sharon Gray:5.3:.97:5:23
southwest:SW:Lewis Dalsass:2.7:.8:2:18
southern:SO:Suan Chin:5.1:.95:4:15
southeast:SE:Patricia Hemenway:4.0:.7:4:17
eastern:EA:TB Savage:4.4:.84:5:20
northeast:NE:AM Main:Jr.:5.1:.94:3
north:NO:Margot Weber:4.5:.89:5:9
central:CT:Ann Stephens:5.7:.94:5:13

#mv datafile.test datafile2

 

# awk -F[:] '{print $3,$1}' datafile2 
Charles Main northwest
Sharon Gray western
Lewis Dalsass southwest
Suan Chin southern
Patricia Hemenway southeast
TB Savage eastern
AM Main northeast
Margot Weber north
Ann Stephens central