-15- command shell entry study notes explain: One of the Three Musketeers awk- built-in functions and custom functions

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Series catalog References Portal: shell introductory study notes - Prologue

awk built-in functions

function	description
int(expr)	Truncated to an integer
sqrt(expr)	Square root
rand()	Returns a random number N, 0and 1range,0<N<1
srand([expr])	Expr used to generate random numbers, if not specified, the default seed current time, if the previous random number seed is used to generate
asort(a,b)	A value of the array is sorted, the sorted values saved to the new array b, a new array subscripts sorted from 1start
asorti(a,b)	A subscript of the array is sorted, supra
sub(r,s[,t])	By recording the input sAlternatively r, tan optional replacement for a field, but only the replacement of a string
gsub(r,s[,t])	By recording the input sAlternatively r, tan optional replacement for a field, replaces all
match(str, regex)	Test string strcontains the matching regexstring
index(str,sub)	Returns the string str index sub is, 0that there is no
length(str) length(arr)	Returns the length of str; Returns the size of the array arr
split(str, arr,regex)	The separator regexwill be strdivided into an arrayarr
substr(s,i[,n])	String taken sfrom ithe start to the length n, if nnot specified, the remaining portion
tolower(str)	strAll uppercase converted to lowercase
toupper(str)	strAll lowercase to uppercase
systime()	The current time in seconds
mktime()	Converting the formatted time to time in seconds
strftime([format[,timestamp[,utc-flag]]])	Formatted output time, a time stamp to a string

Truncate int (var)

admindeMacBook-Pro:myshell admin$ echo "111 11.1 11a 11a1" |awk '{for(i=1;i<=NF;i++) print $i}'
111
11.1
11a
11a1
admindeMacBook-Pro:myshell admin$ echo "111 11.1 11a 11a1" |awk '{for(i=1;i<=NF;i++) print int($i)}'
111
11
11
11
admindeMacBook-Pro:myshell admin$ echo "111 11.1 11a 11a1" |awk '{for(i=1;i<=NF;i++) print +$i}'
111
11.1
11
11

• int(var)Can intercept varthe first appeared in整数
• int(var)It is an integer of interception, and this should be +vardistinguished.

Square root sqrt (expr)

admindeMacBook-Pro:myshell admin$ awk 'BEGIN{print sqrt(9)}'
3

A random number rand () and srand ()

rand()Generated value is fixed, in the range: (0)

admindeMacBook-Pro:~ admin$ awk 'BEGIN{print rand()};'
0.840188
admindeMacBook-Pro:~ admin$ awk 'BEGIN{print rand()};'
0.840188
admindeMacBook-Pro:~ admin$ awk 'BEGIN{print rand();print rand()}'
0.840188
0.394383
admindeMacBook-Pro:~ admin$ awk 'BEGIN{print rand()};'
0.840188

rand()Need to srand()combine in order to make changes in the value of sending generated, can be srand()thought of as a random seed method has changed:

admindeMacBook-Pro:~ admin$ awk 'BEGIN{srand();print rand()};'
0.424539
admindeMacBook-Pro:~ admin$ awk 'BEGIN{srand();print rand()};'
0.780827

By rand()generating a 1~100less random numbers:

admindeMacBook-Pro:~ admin$ awk 'BEGIN{srand();print int(rand()*100)};'
63
admindeMacBook-Pro:~ admin$ awk 'BEGIN{srand();print int(rand()*100)};'
49

Sort Sort standard array values ​​asort (a, b) and a lower array asorti (a, b)

数组值排序asort(a,b)和数组下标排序asorti(a,b)The values ​​are the array after the array is sorted into a b.

# 原始数组
admindeMacBook-Pro:~ admin$ echo 0 |awk 'BEGIN{a[1]="line11";a[3]="line09";a[4]="line12";a[8]="line10"}{for(v in a) print "a["v"]="a[v]}'
a[4]=line12
a[8]=line10
a[1]=line11
a[3]=line09
# asort按照值排序
admindeMacBook-Pro:~ admin$ echo 0 |awk 'BEGIN{a[1]="line11";a[3]="line09";a[4]="line12";a[8]="line10"}{N=asort(a,b);for(j=1;j<=N;j++) print "b["j"]="b[j]}'
b[1]=line09
b[2]=line10
b[3]=line11
b[4]=line12
# asorti按照下标排序
admindeMacBook-Pro:~ admin$ echo 0 |awk 'BEGIN{a[1]="line11";a[3]="line09";a[4]="line12";a[8]="line10"}{N=asorti(a,b);for(j=1;j<=N;j++) print "b["j"]="b[j]}'
b[1]=1
b[2]=3
b[3]=4
b[4]=8

• asortTo 值sort the results into an array b, the array index to abandon the original.
• asortiTo 下标sort the results into an array b, the array abandon the original value.

Alternatively sub field (r, s [, t]) and a global field replacement gsub (r, s [, t])

admindeMacBook-Pro:~ admin$ printf "1 2 3 2 5\n2 5 3 2 1\n1 3 2 1 2\n"
1 2 3 2 5
2 5 3 2 1
1 3 2 1 2
# 替换首个匹配的字段 且 不指定字段
admindeMacBook-Pro:~ admin$ printf "1 2 3 2 5\n2 5 3 2 1\n1 3 2 1 2\n" |awk '{sub(2,0);print $0}'
1 0 3 2 5
0 5 3 2 1
1 3 0 1 2
# 替换全部匹配的字段 且 不指定字段
admindeMacBook-Pro:~ admin$ printf "1 2 3 2 5\n2 5 3 2 1\n1 3 2 1 2\n" |awk '{gsub(2,0);print $0}'
1 0 3 0 5
0 5 3 0 1
1 3 0 1 0
# 替换首个匹配的字段 且 指定字段
admindeMacBook-Pro:~ admin$ printf "1 2 3 2 5\n2 5 3 2 1\n1 3 2 1 2\n" |awk '{sub(2,0,$2);print $0}'
1 0 3 2 5
2 5 3 2 1
1 3 2 1 2
# 替换全部匹配的字段 且 指定字段
admindeMacBook-Pro:~ admin$ printf "1 2 3 2 5\n2 5 3 2 1\n1 3 2 1 2\n" |awk '{gsub(2,0,$2);print $0}'
1 0 3 2 5
2 5 3 2 1
1 3 2 1 2

• sub(r,s)Each row replace only the first matching field.
• gsub(r,s)Replacing all the matching record field of each line.
• sub(r,s)The sub(r,s,t)difference is that the latter only try to match the specified field.

Regular match match (str, regex)

# 存在
admindeMacBook-Pro:~ admin$ awk 'BEGIN{print match("abc123","123")}'
4
# 不存在
admindeMacBook-Pro:~ admin$ awk 'BEGIN{print match("abc123","321")}'
0

String index index (str, sub)

# 单个字符的索引
admindeMacBook-Pro:~ admin$ awk 'BEGIN{print index("hello","h")}'
1
admindeMacBook-Pro:~ admin$ awk 'BEGIN{print index("hello","e")}'
2
# 连续字符的索引
admindeMacBook-Pro:~ admin$ awk 'BEGIN{print index("hello","he")}'
1
admindeMacBook-Pro:~ admin$ awk 'BEGIN{print index("hello","el")}'
2
# 首个匹配的字符
admindeMacBook-Pro:~ admin$ awk 'BEGIN{print index("hello","l")}'
3
# 不存在时，结果为0
admindeMacBook-Pro:~ admin$ awk 'BEGIN{print index("hello","k")}'
0

• From the start index position 1, 0 indicates absence.
• If multiple matches exist, the result shows only the first matching index.

Length of string length ([s])

admindeMacBook-Pro:~ admin$ awk 'BEGIN{a="1111";print length(a)}'
4
admindeMacBook-Pro:~ admin$ awk 'BEGIN{a[1]="1111";a[3]="2222";print length(a)}'
2

• length(var): Length of var
• length(arr): The size of the array arr

Split split (str, arr, regex)

admindeMacBook-Pro:~ admin$ awk 'BEGIN{str="10.20.30.40";split(str,arr,".");for(v in arr) print arr[v]}'
40
10
20
30
admindeMacBook-Pro:~ admin$ awk 'BEGIN{str="10.20.30.40";split(str,arr);for(v in arr) print arr[v]}'
10.20.30.40
admindeMacBook-Pro:~ admin$ awk 'BEGIN{str="10 20 30 40";split(str,arr);for(v in arr) print arr[v]}'
40
10
20
30
admindeMacBook-Pro:~ admin$ awk 'BEGIN{FS=".";str="10.20.30.40";split(str,arr);for(v in arr) print arr[v]}'
40
10
20
30

• If no delimiter regexis used as a delimiter FS.

Interception string substr (s, i [, n])

admindeMacBook-Pro:~ admin$ awk 'BEGIN{str="123haha";print substr(str,3)}'
3haha
admindeMacBook-Pro:~ admin$ awk 'BEGIN{str="123haha";print substr(str,3,2)}'
3h

• substr(s,i): Intercepting string s, starting from all i, until the end.
• substr(s,i,n): Intercepting string s, starting from all i, intercept length is n.

Case conversion tolower (s) and toupper (s)

admindeMacBook-Pro:~ admin$ awk 'BEGIN{s="Hello World";print s;print tolower(s);print toupper(s)}'
Hello World
hello world
HELLO WORLD

System time systime, mktime and strftime

By systimeacquiring the system in seconds:

admindeMacBook-Pro:~ admin$ awk 'BEGIN{print systime()}'
1551088337

By systime("date")acquiring system date:

admindeMacBook-Pro:~ admin$ awk 'BEGIN{system("date");}'
2019年 02月 25日 星期一 17:55:39 CST

By mktime(dataspec)the "YYYY MM DD HH MM SS"the time in seconds date format conversion:

admindeMacBook-Pro:~ admin$ awk 'BEGIN{print systime()}'
1551088808
admindeMacBook-Pro:~ admin$ awk 'BEGIN{print mktime("2019 02 25 17 57 30")}'
1551088650

By strftime([format [, timestamp[, utc-flag]]])time seconds output format:

admindeMacBook-Pro:~ admin$ awk 'BEGIN{print strftime("%Y-%m-%d %H:%M:%S",systime())}'
2019-02-25 18:03:00
admindeMacBook-Pro:~ admin$ awk 'BEGIN{print strftime("%Y-%m-%d %H:%M:%S",mktime("2019 02 25 17 57 30"))}'
2019-02-25 17:57:30

Here is the strftimeformatting characters can be used:

SN	description
%a	The acronym week (Mon-Sun).
%A	Week full name (Monday-Sunday).
%b	Month abbreviation (Jan).
%B	The full name of the month (January).
%c	Local date and time.
%C	Century portion of a year in which the year is divisible by 100.
%d	Decimal date (01-31)
%D	Equivalent to% m /% d /% y.
%e	Date, if there is only one digit is padded with spaces
%F	Equivalent% Y-% m-% d, which is the ISO 8601 standard date format.
%g	Year ISO8610 standard peripheral mold 100 where the addition (00-99). For example, January 1, 1993 belongs to the first 53 weeks of 1992. So, while it was in 1993, Day 1, but its ISO8601 standard year where the week is 1992. Similarly, although the December 31, 1973 belonging to 1973 but it belongs to the first week of 1994. So the standard of ISO8610 Week December 31, 1973 where is 1974 instead of 1973.
%G	The full name of the year where the ISO standard week.
%h	Equivalent% b.
%H	Hours 24 hours format with decimal representation (00-23)
%I	Hour with the 12-hour format decimal representation (00-12)
%j	The first few days (001-366) of the year
%m	Month (01-12)
%M	The number of minutes (00-59)
%n	Newline (ASCII LF)
%p	Duodecimal notation (AM / PM)
%r	Method duodecimal represents time (equivalent to% I:% M:% S% p).
%R	It is equivalent to% H:% M.
%S	Second time value (00-60)
%t	Tabs (tab)
%T	It is equivalent to% H:% M:% S.
in%	Week (1-7) digital representation, 1 for Monday.
% U	The first few weeks of the year (the first Sunday as the start of the first week), 00-53
% V	The first few weeks of the year (the first Monday as the first week of the start), 01-53.
%w	Week (0-6) to a digital representation, 0 represents Sunday.
%W	Decimal representation of the first few weeks (the first Monday as the first week of the beginning) of the year, 00-53.
%x	Local date representation
%X	Local time
%Y	Year mod 100.
%Y	Decimal representation of the full year.
%with	Time zone, represented in the format + HHMM (e.g., format requirements RFC 1036 or RFC 822 header generation time)
%WITH	Time zone name or abbreviation, if no time zone pending output.

awk custom function

grammar

function function_name(param1,param2,...)
{
  body
}

Examples

[worker@c2-a02-126-10-4 hanchao]$ cat func.awk
# sum
function sum(a,b)
{
   return a + b;
}

# avg
function avg(a,b)
{
   return (a + b) / 2;
}

# main
function main(a,b)
{
   print "sum=",sum(a,b);
   print "avg=",avg(a,b);
}

BEGIN{
   main(10,20)
}
[worker@c2-a02-126-10-4 hanchao]$ awk -f func.awk
sum= 30
avg= 15