Shell script (vi)

Shell script (vi)

(2) awk

A, awk programming mode

#awk编程模式分三个阶段: Execute code Snippet before reading input file (identified by the BEGIN keyword)

Execute code snippet after #读取输入文件时执行代码段, reading input file (identified by end keyword)

B, pattern matching

#awk语句由模式 (pattern) and action composition (action).

#匹配空白行

awk '/^$/{print ' a blank line '} ' bkname.txt

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c, records, and domains

#awk将每个输入文件定义为记录, each string in the row is defined as a field, with spaces between fields, tab

#键或其他符号进行分隔, the symbol for a delimited field is called a delimiter. $ is the domain operator, performing actions on the specified domain

The #$1 represents the 1th field, the $ $ = 2nd field, the $ $ represents the 3rd field, and so on, and the $

#如文件num. txt content, delimited by ":", is divided into 4 domains: num, 123, name1, and Test1

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#分隔符也可以使用BEGIN标识中的FS变量来改变

awk ' BEGIN {fs= ': '} {print $ ', ' $ num.txt} '

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d, Relationships, and Boolean operators

#关系运行符 <, <=, >, >=, = =,! =, ~,!~: Less than, less than or equal to, greater than, greater than or equal to

#等于, not equals, matches regular expressions, does not match regular expressions

awk ' BEGIN {fs= ': '} {if ($3<1) print '} '/etc/passwd

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#匹配正则表达式和不匹配正则表达式

awk ' BEGIN {fs= ': '} $2~/123/' Num.txt

awk ' BEGIN {fs= ': '} $2!~/123/' Num.txt

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#布尔运算符 | |, && and!: respectively, for or, with, non-

awk ' BEGIN {fs= ': '} {if ($2==123 | | $4== "Test2") print $} ' Num.txt

awk ' BEGIN {fs= ': '} {if ($1== "num" && $2==122) print $} ' Num.txt

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#算术运算 + 、-、 *,/,%, ^ or * *, ++x, x + + 、--x and x--: Add, subtract, multiply, divide, modulo,

#返回x值前自增1和返回x值之后自增1, returns the X minus 1 and the 1 after the X value is returned

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Awk-f: '/num/{print $5+$2} ' num.txt

Awk-f: '/num/{print $5-$2} ' num.txt

Awk-f: '/num/{print $5*$2} ' num.txt

Awk-f: '/num/{print $5/$2} ' num.txt

Awk-f: '/num/{print $5%$2} ' num.txt

Awk-f: '/num/{print $2^2} ' num.txt

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e, System variables

# $n: Nth field of the current record, divided by FS between domains

#$0: The domain of the record

#ARGC: Number of command-line arguments

#ARGING: The location of the current file in the command line (identified as 0)

#ARGV: Array of command-line arguments

#CONVFMT: Digital Conversion format

#ENVIRON环境变量关联数组

#ERRNO: Description of the last system error

#FIELDWIDTHS: List of field widths, separated by spaces

#FILENAME: Current file name

#FNR: The number of records in a file, that is, how many records (lines) are in the file

#FS: Specify the domain delimiter, which is the default space

#IGNORECASE: Boolean variable, if straight, ignores case matching

#NF: The number of fields in the current record, that is, the current record, the number of fields separated by delimiters

#NR: Current record number, which is currently read to the first record

#OFMT: The output format of a number

#OFS: Output field delimiter, default to Space

#ORS: Output record delimiter, default is line feed

#RLENGTH: The length of the string matched by the match function

#RS: Record delimiter, default to Space

#RSTART: The 1th position of a string matched by the match function

#SUBSEP: Array subscript delimiter, default value is \034

#以 ":" is a delimiter that prints the number of fields in the current record, the number of records, all fields, and the number of file names and records

Awkl ' BEGIN {fs= ': '} {print nf,nr,$0} END {print Filename,fnr} ' Bkname.txt

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F, formatted output

#printf (formatting controls, parameters), the controls start with%, and the parameters are generally domain

#修饰符 "-", "width", and ". Prec", respectively: left-justified, field-step, and multiples to the right of the decimal point

#格式符 "%c", "%d", "%e", "%f", "%o", "%s", and "%x", respectively: ASCII characters, number of shaping

#浮点数, scientific notation, floating point number, octal, string, and hexadecimal

#以 ":" As a delimiter, format the output num.txt 1th and 4th fields

Awk-f: ' {printf (%s\t%f\n,$1,$4)} ' Num.txt

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2 digits after #浮点数长度控制在5位, decimal point

awk ' BEGIN {printf ("%5.2f\n", 20150506.2101)} '

#小浮点数小数点保留3位, and Align Left

Awkl ' BEGIN {printf ("%-.3f\n", 20150506.2101)} '

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g, built-in string functions

#gsub (r,s): replace R with s in the input file

#gsub (r,s,t): replace R with S in T

#index (S,T): Returns the 1th t position of a string in S

#length (s): return s length

#match (S,T): Tests if S contains a string that matches T

#split (r,s,t): R is divided into sequence s on t

#sub (R,S,T): Replaces the 1th occurrence of R in T with the S

#substr (R,s): Returns the suffix part of the string R starting from S, which intercepts the string from S start to end

#substr (R,S,T): Returns the suffix part of the string r from the beginning of the s length to T,

#即截取从s开始长度为t的字符串

#gsub ("name", "*"): Replace name with * in the input file

awk ' BEGIN {fs= ': '} gsub (/name/, ' * ') {print $} ' Num.txt

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#index ("Get_string_index", "string"): Returns the 1th "string" position, starting with 1

awk ' BEGIN {print index ("Get_string_index", "string")} '

#length ("Get_string_length"): Gets the string length

awk ' BEGIN {print length ("Get_string_length")} '

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#match ("Test_string_exist", "string"): Tests whether string strings are contained in Test_string_exist

awk ' BEGIN {print match ("Test_string_exist", "string")} '

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#sub ("Name2", "rep", $): Replace the 1th occurrence of name2 with rep

awk ' BEGIN {fs= ': '} $2~122 sub ("Name2", "Rep", $ $);p rint $} ' Num.txt

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#substr ("Get_string_test", 5): Gets the string starting from 5 characters to the end of the line

#substr ("Get_string_test", 5,6): Gets a string starting from 5 characters with a length of 6 characters

awk ' BEGIN {print substr ("Get_string_test", 5)} '

awk ' BEGIN {print substr ("Get_string_test", 5,6)} '

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H. Passing parameters to the awk script

I, conditional statements and loop statements

#if条件语句.

if (conditional expression)

{

Action

}

Else

{

Action

}

#for循环语句

for (n=0;n<=10;i++)

{

Action

}

#while循环语句, the 1th while executes at least 1 times,

#第2个while可能1次都没有执行 (conditions not met)

Do

{

Action

}

while (conditional expression)

while (conditional expression)

{

Action

}

This article is from the "Love On Action" blog, please be sure to keep this source http://1055745601.blog.51cto.com/5003160/1660417

Shell script (vi)