How to find the size of a directory in linux

We all know "du" command gives the size of the files, but it not convenient to read or understand the size as "du" command gives the size in KB's

In order to  make is human readable format, please follow as mentioned below


du -lsh <directory_name>

du -lsh <file_name>

-h => display the size in human readable format

e.g.,
>> du  -lsh  prabhath_movies
5GB  prabhath_movies

>> du  -lsh  hero.avi
1GB   hero.avi


Thanks for going through this article, Have a good day :-)

Vim Commands

1) How to open file in VI Editor at a specific line

]#  vi  Sample.txt  ++105

ie., From the linux terminal, it will open the Sample.txt  at line 105

2) How can we search word that is under the cursor in VI/VIM

Put the cursor on the word
Press " * " for the next occurrence of the word

3)  a) Replace a pattern with another pattern from line "m" to line "n"

>>cat test.txt

...
49 prabhath kota
50 lakshmi muvvala
51 vamsidar kota
52 prabhath kota
53 prabhath prabhath
54 perl awk
55 prabhath prabhath
56 kota prabhath
...

:50,55s/prabhath/darling/
#It replaces line 50 to line 55, only the first occurance in the line

o/p:

...
49 prabhath kota #49th line
50 lakshmi muvvala
51 vamsidar kota
52 darling kota
53 darling kota
54 perl awk
55 darling kota      //replaced only first occurance
56 kota prabhath #56th line
...


>>cat test.txt

...
49 prabhath kota      #49th line
50 lakshmi muvvala
51 vamsidar kota
52 prabhath kota
53 prabhath prabhath    //replaced all
54 perl awk
55 prabhath prabhath   //replaced all
56 kota prabhath          #56th line
...


:50,55s/prabhath/darling/g
#It replaces line 50 to line 55, all the occurances in the line

o/p:

...
49 prabhath kota #49th line
50 lakshmi muvvala
51 vamsidar kota
52 darling kota
53 darling darling
54 perl awk
55 darling darling
56 kota prabhath #56th line
...


3 b) Replace a pattern with another pattern replacing through out the file

:%s/prabhath/prabhath12345/g


3 c) Replace a pattern with another pattern from the current line to next "n" lines

e.g.,

>> cat test.txt
test test test test
test test test test

#if the cursor is on the 2nd line ("." denotes 2nd line)
#if the cursor is on the 1st line ("." denotes 1st line)

:.,.+2s/test/testabc


o/p:

testabc test test test
testabc test test test


:.,.+2s/test/testabc/g
# "g" is for all the occurances in the current line

o/p:

testabc testabc testabc testabc
testabc testabc testabc testabc


4) To remove the last character from every line in the file. 

Use it if every line in the file ends with ^M as the result of a file transfer.
Execute it when the cursor is on the first line of the file.

:%s/.$//

Note:
$ -> denotes end of the line
^ -> denotes start of the line


5) To remove the first character from every line in the file. 

:%s/^.//

Note:
$ -> denotes end of the line
^ -> denotes start of the line



6) How to search in Vim

" Show all tabs:

/\t


" Show and Replace trailing(ending) whitespace:

:%s/\s\+$//gc


" Show spaces before a tab:

/\+\ze\t



7) Edit new file from the current viewing of the file...

Suppose you already opened test.txt, suppose you are trying to open new.txt now..

gvim test.txt

after that you want to close test.txt and open new.txt, then you can do like...

:e new.txt




8) How to access multiple files from the same window 

]# vim  test_1.txt         #Which opens test_1.txt

After editing this file, without closing or coming out of this file, do you know how to edit another file from the same window

:e test_2.txt      #Which opens test_2.txt

Now you want to go reopen the previous file test_1.txt

:e#                  #Now you have already opened test_2.txt, but this reopens test_1.txt

after this, if you try to give the command again, it reopens previous file test_2.txt

:e#                  ##Now you have already opened test_1.txt, but this reopens test_2.txt


This trick helps you a lot when you have to work switching back to back two files and this way you can easily reopen the previous file without much typing effort



9) How to Split screen

Horizontally:

vi test.txt

:split new.txt


Vertically:

vi test.txt

:vsplit new.txt

Note:
Cntrl + ww //To change the window from one to another


9) Move the cursor to beginning of line in Vim Editor

$ takes you to the end of the line


10) Move the cursor to beginning of line in Vim Editor


^ takes you to the first non-whitespace character in the line, and

0 (zero) takes you to the beginning of the line including whitespace

Cron Job Basics - Crontab

crontab -e      Edit your crontab file, or create one if it doesn’t already exist.
crontab -l      Display your crontab file.
crontab -r      Remove your crontab file.
crontab -v      Display the last time you edited your crontab file. (This option is only available on a few systems.)


min    0-59
hour   0-23
day    1-31
mon    1-12
dow    0-6 (Sunday = 0, Saturday = 6) DOW => Day of Week


min hr day month Week
30 00 01 01,06,12 * –> 00:30 Hrs on 1st of Jan, June & Dec.
00 20 * 10 01-05 –> 8.00 PM every weekday (Mon-Fri) only in Oct
00 00 01,10,15 * * –> midnight on 1st ,10th & 15th of month
05,10 00 10 * 01 –> At 12.05,12.10 every Monday & on 10th of every month
05 00 01 01 * -> 00:05 Hrs on 1st of Januray of each year

The asterisk in the field indicates to cron that any day of the week is acceptable.
However, since an explicit month and day have been specified, the day of the week is effectively ignored.


How to create a cron job that will run on the last day of each month, considering the fact that a month could have 28, 29, 30 or 31 days ?

Ans:
Your script, however, can test for that and exit if it is not the last day.
So - you'd set it in cron to run on the 28, 29, 30 and 31. Your script decides if it really is the last day and exits if it is not.
Or you can put each month into crontab separately and just deal with February in your script.


min hr day month Week
30 20 28,29 02 * /usr/prabhath/run.pl -> 8.30 PM every 28th of Feb
30 20 30 04,06,09,11 * /usr/prabhath/run.pl -> 8.30 PM every 30th of Months having 30 days
30 20 31 01,03,05,07,08,10,12 * /usr/prabhath/run.pl -> 8.30 PM every 31th of Months having 31 days

More Examples:
################
min hr day month Week User Command
01 * * * * root echo "This command is run at one min past every hour"
17 08 * * * root echo "This command is run daily at 8:17 am"
17 20 * * * root echo "This command is run daily at 8:17 pm"
00 04 * * 0 root echo "This command is run at 4 am every Sunday"
42 04 01 * * root echo "This command is run 4:42 am every 1st of the month"
01 * 19 07 * root echo "This command is run hourly on the 19th of July"


Example:
############
min hr day month Week User Command
* 12 16 * Mon root cmd

Will run cmd at midday every Monday and every 16th, and will produce the
same result as both of these entries put together would:
* 12 16 * * root cmd
* 12 * * Mon root cmd

Example:
############

min hr day month Week User Command
59 11 * * 1,2,3,4,5 root backup.sh
equals to
59 11 * * 1-5 root backup.sh


Step Values:
#################
Cron also supports 'step' values.
*/2 in the dom field would mean the command runs every two days and likewise,
*/5 in the hours field would mean the command runs every 5 hours.

Example:
############

min hr day month Week User Command
* 12 10-16/2 * * root backup.sh
is the same as:
* 12 10,12,14,16 * * root backup.sh

E.g.,

min hr day month Week User Command
*/15 9-17 * * * root connection.test
Will run connection.test every 15 mins between the hours or 9am and 5pm


min hr day month Week User Command
* 12 1-15,17,20-25 * * root cmd
Will run cmd every midday between the 1st and the 15th as well as the 20th and 25th (inclusive) and also on the 17th of every month.


O/P from Cron:
###################

min hr day month Week User Command
*/15 9-17 * * * root connection.test | mail -s "Subject" prabhathkota@gmail.com

*/15 9-17 * * * root connection.test >/dev/null 2>&1 #It won't send mail to anyone

*/15 9-17 * * * root connection.test > log.file

*/15 9-17 * * * root connection.test > log.file 2>&1

*/15 9-17 * * * root connection.test > mail -s "logfile for cmd" <log.file

*/15 9-17 * * * root connection.test >


Disable Email in Cronjob
#########################
By default cron jobs sends a email to the user account executing the cronjob. If this is not needed put the following command At the end of the cron job line .
>/dev/null 2>&1

Word Count - Unix

>> wc test.txt

15  43 282 test.txt

ie.,

15 lines
43 words
282 chars


>>wc -l test.txt    #Lines
15 test.txt


>> wc -c test.txt    #Words
282 test.txt


>> wc -w test.txt    #Characters
43 test.txt

How to print first two columns of a file - AWK

1) It will print first line alone

>>awk 'NR==1' test.txt #1st line from the top
>>awk 'NR==7' test.txt #7th line from the top

2) How to print first line/lines of the file

>>head -8 test.txt

How to print last two columns of a file - AWK

1) How to print last two columns of a file?

NF => prints the last line

>>cat test.txt
prabhath   kota   Jan
lakshmi     muvvala   Feb
PRABHATH    KOTA   Mar
LAKSHMI       MUVVALA   Apr

>>awk '{print $(NF-1),"\t",$NF}' test.txt #RIGHT

output:
kota              Jan
muvvala         Feb
KOTA           Mar
MUVVALA  Apr

>>awk '{print $NF-1,"\t",$NF}' test.txt #WRONG


2) How to print last two columns of a command?

>> ls
-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

>>ls -l | awk '{print $(NF-1),"\t",$NF}'

output:
12:51 a.txt
10:18 b.txt
15:25 c.txt


3) How to print the last line/lines of the file

>>tail -f test.txt
>>tail -4 test.txt #Prints Last 4 lines
>>tail -1 test.txt #Prints Last line of the file

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

Unix Grep Examples

Grep
######

1) How to exclude lines in a grep

syntax: grep -v <pattern> <filename>

e.g.,
>> cat test.txt
prabhath
ramesh
vamsi
lakshmi muvvala
PRABHATH
LAKSHMI MUVVALA

>> grep -v "prabhath" test.txt

It will exclude the lines which contain "prabhath"

o/p:
ramesh
vamsi
lakshmi muvvala
PRABHATH
LAKSHMI MUVVALA


2) How to exclude lines in a grep with ignore case

syntax: grep -iv <pattern> <filename>

e.g.,
>> cat test.txt
prabhath
ramesh
vamsi
lakshmi muvvala
PRABHATH
LAKSHMI MUVVALA

>> grep -iv "prabhath" test.txt

It will exclude the lines which contain "prabhath", "Prabhath", "PRABAHTAH" etc.,

o/p:
ramesh
vamsi
lakshmi muvvala
LAKSHMI MUVVALA

3) How to exclude lines which contain multiple patterns at one shot

Syntax: grep -v -e <pattern> -e <pattern> <filename>

e.g.,
>> cat test.txt
prabhath
ramesh
vamsi
lakshmi muvvala
PRABHATH
LAKSHMI MUVVALA


>>grep -v -e "prabhath" -e "lakshmi" test.txt

It will exclude the lines which contains the pattern "prabhath" & pattern "lakshmi"

o/p:
ramesh
vamsi
PRABHATH
LAKSHMI MUVVALA


>>grep -iv -e "prabhath" -e "lakshmi" test.txt

Please note "i" - ignore case
It will exclude the lines which contains the pattern "prabhath", "PRABHATH" & pattern "lakshmi", "LAKSHMI"

o/p:
ramesh
vamsi


4) Counting the number of matches using grep -c

Syntax: grep -c "pattern" filename

e.g.,
>> cat test.txt
prabhath
ramesh
vamsi
lakshmi muvvala
PRABHATH
LAKSHMI MUVVALA

>>grep -c "prabhath" test.txt
1

>>grep -ic "prabhath" test.txt
2


5) Counting the number of lines that does not match the pattern

e.g.,
>> cat test.txt
prabhath
ramesh
vamsi
lakshmi muvvala
PRABHATH
LAKSHMI MUVVALA

>>grep -vc prabhath test.txt
5

(or)

>>grep -v -c prabhath test.txt
5


6) Display N lines around match (Before & After)

Syntax: > grep -C 2 "Pattern" File

e.g.,
>> cat test.txt
prabhath
ramesh
vamsi
lakshmi muvvala
PRABHATH
LAKSHMI MUVVALA


>> grep -C 2 "lakshmi" test.txt

o/p:
ramesh
vamsi
lakshmi muvvala //Actual Match
PRABHATH
LAKSHMI MUVVALA


7) Display N lines Before Match

Syntax: > grep -B 2 "Pattern" File

e.g.,
>> cat test.txt
prabhath
ramesh
vamsi
lakshmi muvvala
PRABHATH
LAKSHMI MUVVALA

>> grep -B 2 "lakshmi" test.txt

o/p:
ramesh
vamsi
lakshmi muvvala //Actual Match


8) Display N lines After Match

Syntax: >> grep -A 2 "Pattern" File

e.g.,
>> cat test.txt
prabhath
ramesh
vamsi
lakshmi muvvala
PRABHATH
LAKSHMI MUVVALA

>> grep -A 2 "lakshmi" test.txt

o/p:
lakshmi muvvala //Actaul Match
PRABHATH
LAKSHMI MUVVALA


9)  Checking for full words, not for sub-strings using grep -w

e.g.,
>> cat test.txt
prabhath
prabhathkota
prabhath kota
ramesh
vamsi
lakshmi muvvala
PRABHATH
PRABHATHKOTA
PRABHATH KOTA
LAKSHMI MUVVALA

Syntax: >> grep -w "Pattern" File

>>grep -iw "kota" test.txt

o/p:
prabhath kota
PRABHATH KOTA


>>grep -i "kota" test.txt

o/p:
prabhathkota
prabhath kota
PRABHATHKOTA
PRABHATH KOTA


10) How to get line numbers in grep

>> cat test.txt
prabhath
prabhathkota
prabhath kota
ramesh
vamsi
lakshmi muvvala
PRABHATH
PRABHATHKOTA
PRABHATH KOTA
LAKSHMI MUVVALA


>> grep -n 'PRABHATH' test.txt

o/p:
7 PRABHATH
8 PRABHATHKOTA
9 PRABHATH KOTA

>> grep -in 'PRABHATH' test.txt

o/p:
1 prabhath
2 prabhathkota
3 prabhath kota
7 PRABHATH
8 PRABHATHKOTA
9 PRABHATH KOTA


11) Grep Pipe Examples

1) Display cpu model name

#With Pipe
]# cat /proc/cpuinfo | grep -i 'Model'

#Without Pipe
]# grep -i 'Model' /proc/cpuinfo    

2) grep dbname *.dbl | grep mysql


12) Some complex examples using Grep...

>> cat test.txt
prabhath
prabhathkota
prabhath kota
ramesh
vamsi
lakshmi muvvala
PRABHATH
PRABHATHKOTA
PRABHATH KOTA
LAKSHMI MUVVALA


>> grep -nC 2 'lakshmi' test.txt

Note: "-C 2" will grep for 2 lines above and 2 lines below
          "-n" will give the line numbers

o/p:
4 ramesh
5 vamsi
6 lakshmi muvvala
7 PRABHATH
8 PRABHATHKOTA


13) Grep OR

1) grep 'pattern1\|pattern2' filename

$ cat employee.txt
100  Thomas  Manager    Sales       $5,000
200  Jason   Developer  Technology  $5,500
300  Raj     Sysadmin   Technology  $7,000
400  Nisha   Manager    Marketing   $9,500
500  Randy   Manager    Sales       $6,000


$ grep 'Tech\|Sales' employee.txt
100  Thomas  Manager    Sales       $5,000
200  Jason   Developer  Technology  $5,500
300  Raj     Sysadmin   Technology  $7,000
500  Randy   Manager    Sales       $6,000

2) grep -E 'pattern1|pattern2' filename

$ grep -E 'Tech|Sales' employee.txt
100  Thomas  Manager    Sales       $5,000
200  Jason   Developer  Technology  $5,500
300  Raj     Sysadmin   Technology  $7,000
500  Randy   Manager    Sales       $6,000


3) egrep 'pattern1|pattern2' filename

$ egrep 'Tech|Sales' employee.txt
100  Thomas  Manager    Sales       $5,000
200  Jason   Developer  Technology  $5,500
300  Raj     Sysadmin   Technology  $7,000
500  Randy   Manager    Sales       $6,000


14) Grep AND

grep -E 'pattern1.*pattern2' filename
grep -E 'pattern1.*pattern2|pattern2.*pattern1' filename

$ grep -E 'Dev.*Tech' employee.txt
200  Jason   Developer  Technology  $5,500

The following example will grep all the lines that contain both “Manager” and “Sales” in it (in any order).
$ grep -E 'Manager.*Sales|Sales.*Manager' employee.txt


15) Grep NOT

grep -v 'pattern1' filename

$ grep -v Sales employee.txt
200  Jason   Developer  Technology  $5,500
300  Raj     Sysadmin   Technology  $7,000
400  Nisha   Manager    Marketing   $9,500

$ egrep 'Manager|Developer' employee.txt | grep -v Sales
200  Jason   Developer  Technology  $5,500
400  Nisha   Manager    Marketing   $9,500


16) Highlighting the search using GREP_OPTIONS

$ export GREP_OPTIONS='--color=auto' GREP_COLOR='100;8'

$ grep this demo_file
this line is the 1st lower case line in this file.
Two lines above this line is empty.
And this is the last line.



17) Show only the matched string

#] grep -o  

$ grep -o "is.*line" demo_file

is line is the 1st lower case line
is line
is is the last line