1) To fetch selected columns from a command using AWK
e.g.,
>> ls -l
-rw-r----- 1 kotaprax users 203 Nov 22 12:51 new.txt
-rw-r----- 1 kotaprax users 100 Nov 22 12:51 new1.txt
-rw-r----- 1 kotaprax users 126 Nov 23 12:57 output.txt
-rw-r----- 1 kotaprax users 282 Nov 23 10:18 test.txt
-rw-r----- 1 kotaprax users 17 Nov 16 15:25 test1.txt
From the abvoe command, we are deriving some columns
>> ls -l | awk '{print $3 "\t" $8 "\t" $9}'
kotaprax 12:51 new.txt
kotaprax 12:51 new1.txt
kotaprax 12:57 output.txt
kotaprax 10:18 test.txt
kotaprax 15:25 test1.txt
2) How to print first column from the file using AWK
e.g.,
>> cat test.txt
prabhath kota
lakshmi muvvala
PRABHATH KOTA
LAKSHMI MUVVALA
>>awk '{print $1}' test.txt
(or)
>>awk < test.txt '{ print $1 }'
o/p:
>>cat test.txt
prabhath
lakshmi
PRABHATH
LAKSHMI
3) How to copy the files using AWK
>> ls
a.txt
b.txt
c.txt
It will copy file.txt to file.txt.new for all the txt files
>>ls *.txt | awk '{print "cp "$1" "$1".new"}' | sh
o/p:
>> ls
a.txt
b.txt
c.txt
a.txt.new
b.txt.new
c.txt.new
4) How to list only directories using awk
>>ls
a.txt
b.txt
c.txt
prabhath_test
o/p:
>> ls -l | grep '^d'
#Lists only directories, since directories start with
drwxr-x--- 2 kotaprax users 1024 Nov 23 13:57 prabhath_test
>>ls -l | grep -v '^d' #Lists only files but not directories
-rw-r----- 1 kotaprax users 203 Nov 22 12:51 a.txt
-rw-r----- 1 kotaprax users 282 Nov 23 10:18 b.txt
-rw-r----- 1 kotaprax users 17 Nov 16 15:25 c.txt
5) Remove files using AWK
>>ls
a.txt
b.txt
c.txt
prabhath_test
a.tt
b.tt
>> ls -l *.tt | awk '{print "rm -r "$9}' | sh
#"rm" is a command, in order to execute, "sh" is used
o/p:
>>ls
a.txt
b.txt
c.txt
prabhath_test
6) AWK - Difference between $0 and $1
>> echo "hello1 hello2 hello3" | awk ' {print $0} ' #$0 prints the whole
hello1 hello2 hello3
>> echo "hello1 hello2 hello3" | awk ' {print $3} ' #$1 prints 1st column
hello3
7) How to print 1st column of a file into another file ?
>>cat test.txt
prabhath kota
lakshmi muvvala
PRABHATH KOTA
LAKSHMI MUVVALA
>> awk '{print $1}' test.txt > output.txt
o/p:
>>cat test.txt
prabhath
lakshmi
PRABHATH
LAKSHMI
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