Snippets

Question 1

How to compress using tar

Answer 1

tar -zcvf archive-name.tar.gz directory-name

Where,

• <kbd>-z<kbd> : Compress archive using gzip program</kbd></kbd>
• <kbd>-c</kbd>: Create archive
• <kbd>-v</kbd>: Verbose i.e display progress while creating archive
• <kbd>-f</kbd>: Archive File name

Question 2

How to uncompress using tar

Answer 2

$ tar -zxvf prog-1-jan-2005.tar.gz
Where,

• <kbd>-x</kbd>: Extract files

Question 3

Checking the size of a folder

Answer 3

$ du -sh

Question 4

Tmux start a new session

Answer 4

tmux new -s [name of session]

Question 5

Check tmux sessions

Answer 5

tmux ls

Question 6

Detach from tmux session

Answer 6

ctrl+b d

Question 7

In tmux, to split a pane horizontally

Answer 7

ctrl+b "

Question 8

In tmux, To split pane vertically

Answer 8

ctrl+b %

Question 9

In tmux to move from pane to pane

Answer 9

ctrl+b [arrow key]

Question 10

In tmux, expand the pane down a few lines

Answer 10

ctrl+b :

Question 11

Tmux, Kill named session

Answer 11

tmux kill-session -t [name of session]

Question 12

tmux, Kill current pane

Answer 12

ctrl+b x

Question 13

Kill tmux server, along with all sessions:

Answer 13

tmux kill-server

Question 14

A very simple backup script

Answer 14

#!/bin/bash OF=/var/my-backup-$(date +%Y%m%d).tgz tar -czvf $OF /home/me/

Question 15

Functions and Local variables in bash.

Answer 15

HELLO=Hello function hello { local HELLO=World echo $HELLO } echo $HELLO hello echo $HELLO

Question 16

Check the size of a specific folder?

Answer 16

du -sch Dir1 File1

Question 17

If statement in bash

Answer 17

#!/bin/bash T1="foo" T2="bar" if ["$T1" = "$T2"]; then echo expression evaluated as true else echo expression evaluated as false fi

Question 18

For in bash

Answer 18

#!/bin/bash for i in `seq 1 10`; do echo $i done

Question 19

bash for loop ten times

Answer 19

#!/bin/bash for i in `seq 1 10`; do echo $i done

Question 20

bash while statement

Answer 20

#!/bin/bash COUNTER=0 while [$COUNTER -lt 10]; do echo The counter is $COUNTER let COUNTER=COUNTER+1 done

Question 21

Bash Until Statement

Answer 21

#!/bin/bash COUNTER=20 until [$COUNTER -lt 10]; do echo COUNTER $COUNTER let COUNTER-=1 done

Question 22

Bash function with parameters

Answer 22

#!/bin/bash function quit { exit } function e { echo $1 echo $2 } e Hello Bye

Question 23

Using select to make simple menus

Answer 23

#!/bin/bash OPTIONS="Hello Quit" select opt in $OPTIONS; do if ["$opt" = "Quit"]; then echo done exit elif ["$opt" = "Hello"]; then echo Hello World else clear echo bad option fi done

Question 24

BAsh script to do backup for a specific folder. The folder to be backed up given in argument to the script.

Answer 24

#!/bin/bash if [-z "$1"]; then echo usage: $0 directory exit fi SRCD=$1 TGTD="/home/alhaol/" OF=\_BackUp\_$(date +\_%Y\_%\_m\_%d).tgz tar -czvf $TGTD$SRCD$OF $SRCD echo ====================================== echo =====================Done =========== echo check $TGTD$SRCD$OF

Question 25

Use cw to find how many lines in a file?

Answer 25

wc -l file

Question 26

Use wc to count the number of words?

Answer 26

wc -w fileName

Question 27

use ls and wc to find number of files in a folder.

Answer 27

ls FolderName | wc -l

Question 28

Use head to show first 2 line in a file:

Answer 28

head -n 2 FileName

Question 29

How to add header line to a file using echo, >, and cat

Answer 29

echo “A, B, C”> header.txt

cat header.csv file.csv > Newfile.csv

Question 30

How to use sed to change the content of a file?

Answer 30

sed “s/<string>/<string>/g" <source_file> &gt; <target_file></target_file></source_file></string></string>

Question 31

use grep and wc to find how many times something happened in a file.

Answer 31

grep “Something” File | wc -l

Question 32

use sed and > to find a pattern in a file and change it to something else

Answer 32

sed “s/somthing/somethingelse/g” adult.csv > adult.csv

Question 33

Using head and tail to sub set large file

Answer 33

head -n 120 adult.csv | tail -n 20 > adult_sample.csv

Question 34

Finding number of duplicate lines is a file using uniq, sort and wc.

Answer 34

sort file.csv | uniq -d | wc -l

Question 35

how to use for loop to replace spaces with _

Answer 35

replace_source=’ ‘

replace_target=’_’

for filename in ./*.csv; do new_filename=${filename//$replace_source/$replace_target}

mv “$filename” “$new_filename”

done