Execute Perl or Python or PHP online

I come across a very good site where you can run perl online and see the results.

http://www.compileonline.com/execute_perl_online.php

Advantages:
Just write the code (in the left panel) and run on the fly.
If case of any errors, it is shown on the right panel
They also prive an input.txt (in one of the tab) and practice reading/writing files
When you click on Multiple Files, it also gives support.pm, we can practice package concepts.

You can also run online Python/PHP/Java/Shell/JavaScript/HTML etc.,

Python:
http://www.compileonline.com/execute_python3_online.php

PHP:
http://www.compileonline.com/execute_php_online.php

Java:
http://www.compileonline.com/compile_java_online.php

Shell Scripting:
http://www.compileonline.com/execute_ksh_online.php

Java Script:
http://www.compileonline.com/try_javascript_online.php

HTML:
http://www.compileonline.com/try_html5_online.php

and many more on home page

http://www.compileonline.com/

Awk Examples

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