Linux三大剑客之awk

[awk@GeekDevOps ~]$ ls -l /bin/*awk
lrwxrwxrwx. 1 root root      4 11月 20 10:41 /bin/awk -> gawk
-rwxr-xr-x. 1 root root 514136 6月  10 2014 /bin/dgawk
-rwxr-xr-x. 1 root root 428576 6月  10 2014 /bin/gawk
-rwxr-xr-x. 1 root root   3188 6月  10 2014 /bin/igawk
-rwxr-xr-x. 1 root root 428600 6月  10 2014 /bin/pgawk

[awk@GeekDevOps ~]$ whatis awk gawk dgawk pgawk igawk
awk (1)              - pattern scanning and processing language
gawk (1)             - pattern scanning and processing language
dgawk (1)            - pattern scanning and processing language
pgawk (1)            - pattern scanning and processing language
igawk (1)            - gawk with include files

[awk@GeekDevOps ~]$ echo "1)  Amit    Physics  80
> 2)  Rahul   Maths    90
> 3)  Shyam   Biology  87
> 4)  Kedar   English  85
> 5)  Hari    History  89">marks.txt

BEGIN {awk-commands}

/pattern/ {awk-commands}

END {awk-commands}

[awk@GeekDevOps ~]$ awk BEGIN'{printf "Sr NO\tName\tSub\tMarks\n"} {print} END{print "Done!"}' marks.txt
Sr NO   Name    Sub     Marks
1)  Amit    Physics  80
2)  Rahul   Maths    90
3)  Shyam   Biology  87
4)  Kedar   English  85
5)  Hari    History  89
Done!
[awk@GeekDevOps ~]$ awk BEGIN'{printf "Sr NO\tName\tSub\tMarks\n"} END{print "Done!"}' marks.txt
Sr NO   Name    Sub     Marks
Done!

awk 'program' input-file1 input-file2 …

awk -f program-file input-file1 input-file2 …

#!/bin/awk -f
BEGIN{print "My name is Ivan Du！"}

[awk@GeekDevOps ~]$ chmod u+x GeekDevOps.awk
[awk@GeekDevOps ~]$ ./GeekDevOps.awk
My name is Ivan Du！

[awk@GeekDevOps ~]$ cat best.txt
www     CC      ICBC
[awk@GeekDevOps ~]$ awk '{print $1}' best.txt
www
[awk@GeekDevOps ~]$ awk '{print $3}' best.txt
ICBC
[awk@GeekDevOps ~]$ awk -F "\t" '{print $3}' best.txt
ICBC

[awk@GeekDevOps ~]$ awk '/a/ {print $3 " " $4}' marks.txt
Maths 90
Biology 87
English 85
History 89

[awk@GeekDevOps ~]$ awk '/u/ {print $4"\t"$3}' marks.txt
90      Maths

[awk@GeekDevOps ~]$ awk 'BEGIN{ct=0} {++ct} END{print "Count:",ct}' marks.txt
Count: 5

[awk@GeekDevOps ~]$ awk '/a/ {++ct} END{print "Count:",ct}' marks.txt
Count: 4

[awk@GeekDevOps ~]$ awk 'length($0) > 22' marks.txt
1)  Amit    Physics  80
2)  Rahul   Maths    90
3)  Shyam   Biology  87
4)  Kedar   English  85
5)  Hari    History  89

[awk@GeekDevOps ~]$ awk 'BEGIN{print "Arguments=" ARGC}' One Two Three Four
Arguments=5

[awk@GeekDevOps ~]$ awk 'BEGIN{for (i=0 ;i<ARGC-1;++i ){printf "ARGC[%d]=%s\n",i,ARGV[i]}}' One Two Three Four
ARGC[0]=awk
ARGC[1]=One
ARGC[2]=Two
ARGC[3]=Three

[awk@GeekDevOps ~]$ awk 'BEGIN{print ENVIRON["PATH"]}'
/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/home/awk/.local/bin:/home/awk/bin

[awk@GeekDevOps ~]$ awk 'END{print FILENAME}' marks.txt 
marks.txt

[awk@GeekDevOps ~]$ awk -F " " '{print $4}' marks.txt 
80
90
87
85
89
[awk@GeekDevOps ~]$ awk '{print $3}' marks.txt 
Physics
Maths
Biology
English
History
[awk@GeekDevOps ~]$ awk 'BEGIN{FS=" "}{print $3}' marks.txt 
Physics
Maths
Biology
English
History

[awk@GeekDevOps ~]$ ls -al | awk 'BEGIN{size=0}{size+=$5}END{print size/1024/1024 "MB"}'
128.017MB
[awk@GeekDevOps ~]$ ls -al|awk 'NR>1{size+=$5} END{print size/1024/1024 "MB"}'
128.017MB

[awk@GeekDevOps ~]$ ls -al|awk 'NR==1{print $2/1024 "MB"}'
128.035MB

[awk@GeekDevOps ~]$ awk 'BEGIN{print "OFS=" OFS}' marks.txt
OFS=

[awk@GeekDevOps ~]$ awk 'BEGIN{A=2.8;B=7;print A/B}'
0.4

[awk@GeekDevOps ~]$ awk 'BEGIN{A=2.8;A=+A;print A}'
2.8

[awk@GeekDevOps ~]$ awk 'BEGIN{A=2.8;A=A^3;print A}'
21.952
[awk@GeekDevOps ~]$ awk 'BEGIN{A=2.8;A=A**3;print A}'
21.952

[awk@GeekDevOps ~]$ awk 'BEGIN{str1="Hello";str2=",GeekDevOps";str3=str1 str2;print str3}'
Hello,GeekDevOps

[awk@GeekDevOps ~]$ awk 'BEGIN{array[0][0]=2;array[0][1]=3;array[1][0]=4;array[1][1]=8;for(i=0;i<2;i++){for(j=0;j<2;j++){printf "array[%d][%d]=%d\n",i,j, array[i][j]}}delete array[0][0];print array[0][0] "\t" array[0][0]}'
array[0][0]=2
array[0][1]=3
array[1][0]=4
array[1][1]=8

[awk@GeekDevOps ~]$ awk 'NF != 4 {
    printf("%s:%d: skipped: NF != 4\n", FILENAME, FNR) > "/dev/stderr"
    next
}'

-:1: skipped: NF != 4

-:2: skipped: NF != 4
...

[awk@GeekDevOps ~]$ awk 'BEGIN {
    if (("date" | getline date_now) <= 0) {
        print "Can not get system date" > "/dev/stderr"
        exit 1
    }
    print "Current date is", date_now
    close("date")
}'
Current date is 2018年 02月 28日 星期三 23:05:16 CST

Return the arctangent of y / x in radians. You can use ‘pi = atan2(0, -1)’ to retrieve the value of pi.

Return the cosine of x, with x in radians.

Return the exponential of x (e ^ x) or report an error if x is out of range. The range of values x can have depends on your machine’s floating-point representation.

Return the nearest integer to x, located between x and zero and truncated toward zero. For example, int(3) is 3, int(3.9) is 3, int(-3.9) is -3, and int(-3) is -3 as well.

Return the natural logarithm of x, if x is positive; otherwise, return NaN (“not a number”) on IEEE 754 systems. Additionally, gawk prints a warning message when x is negative.

Return a random number. The values of rand() are uniformly distributed between zero and one. The value could be zero but is never one.

Return the sine of x, with x in radians.

Return the positive square root of x. gawk prints a warning message if x is negative. Thus, sqrt(4) is 2.

Set the starting point, or seed, for generating random numbers to the value x. 

asort(arr [, d [, how] ])
asorti(arr [, d [, how] ])
gsub(regex, sub, string)
index(str, sub)
length(str)
match(str, regex)
split(str, arr, regex)
sprintf(format, expr-list)
strtonum(str)
sub(regex, sub, string)
substr(str, start, l)
tolower(str)
toupper(str)

systime
mktime(datespec)
strftime([format [, timestamp[, utc-flag]]])

and
compl
lshift
rshift
or
xor

[awk@GeekDevOps ~]$ echo -e "My name is IVAN DU.\nMy blog is GeekDevOps.\nWelcome to my blog."|awk '/My+/'
My name is IVAN DU.
My blog is GeekDevOps.
[awk@GeekDevOps ~]$ echo -e "My name is IVAN DU.\nMy blog is GeekDevOps.\nWelcome to my blog."|awk '/^W/'
Welcome to my blog.