Udemy Linux

Question 1

Open Terminal

Answer 1

Ctrl + Alt + D

Question 2

Close Terminal

Answer 2

Ctrl + D

Question 3

echo

Answer 3

Prints out what you give it

Question 4

cal

Answer 4

Calendar

Question 5

date

Answer 5

today’s date & time

Question 6

clear

Answer 6

clear screen

Question 7

history

Answer 7

all previous commands

Question 8

to run command in history

Answer 8

! + line #

Question 9

!!

Answer 9

run most recent command

Question 10

history -c; history -w

Answer 10

clears history and makes changes permanent

Question 11

exit

Answer 11

terminal closes

Question 12

echo $PATH

Answer 12

current path

Question 13

which

Answer 13

which folder a command is in

Question 14

operand

Answer 14

input

Question 15

man

Answer 15

man pages

Question 16

man “-k” “which”

Answer 16

man page ; search ; for term “which” –> man (section number) “result title”

Question 17

>

Answer 17

standard output; #1; also 1>; will truncate

Question 18

> >

Answer 18

output; append file

Question 19

tty

Answer 19

see path of terminal

Question 20

<

Answer 20

standard INPUT

Question 21

cut

Answer 21

cuts files and returns specific columns (“fields”); –delimiter –> give it what divides the columns; –fields –> how many to output

Question 22

|

Answer 22

pipe data from standard input to next command for standard input

Question 23

tee

Answer 23

causes data to flow in two directions; saves to file as directed; allows file to be saved to continue piping

Question 24

xargs

Answer 24

(not all commands accept standard input, some only accept command line arguments) converts data from standard input and puts it into command line argument; can use command | xargs; command such as “echo”; command such as “cat” | xargs “rm”

Question 25

rm

Answer 25

delete

Question 26

.bash_aliases

Answer 26

file in home folder for aliases –> alias aliasName=”command1 -options args | command 2 -options args …” (make sure first command can be piped to, using xargs, if needed) –> restart terminal

Question 27

pwd

Answer 27

print working directory; ~ –> home directory

Question 28

absolute path

Answer 28

full path

Question 29

ls -F

Answer 29

classiFy –> slash at the end is a directory (folder);

Question 30

cd

Answer 30

change directory; ~(start at Home Directory)/; .=current directory; ..=parent folder or folder above

Question 31

ls -a

Answer 31

show hidden files; hidden files start with .

Question 32

touch

Answer 32

creates new empty files; touch // to create files inside directories / “folders”

Question 33

create file with content inside

Answer 33

echo “” > ___fiel name_____.txt

Question 34

mkdir

Answer 34

make directory; mkdir -p –> to create entire PATH; mkdir / –> will create folders inside folder

Question 35

rm

Answer 35

remove file or directory

Question 36

rm -r

Answer 36

delete recursively…delete the item and everything inside it; rm -ri (interactive, to have the r option ask for permission for each deletion)

Question 37

rmdir

Answer 37

remove empty directory

Question 38

cp

Answer 38

copy; cp -r –> copy the folder & everything inside (recursively)

Question 39

locate

Answer 39

locate files; locate -i –> search in case insensitive way; locate –limit # –> limit to number of files; locate -S –> get information about database itself; locate -e –> check to see if files existed before reporting them / locate –existing; locate –follow / locate -L –> check links; (ONLY LISTS FILES)

Question 40

updatedb

Answer 40

update database

Question 41

find

Answer 41

DEFAULT BEHAVIOR: list every file & folder that is inside the current folder & lower down in the file system; always up-to-date (doesn’t use database); use “/” to list all files & folders in system; can be used to list all contents in folders by using file path; file -maxdepth # to control number of levels find command searches; find . (current directory) -type f (for type: file) d (for type: directory/ “folder”) –> can be combined with maxdepth option using maxdepth FIRST; find . -name “” –> place name in quotes; find . -maxdepth 10 -iname “?.TXT” –> ignore case in name search (case insensitive); sudo find / (starting at root directory, so use sudo command to avoid permission denied from getting access to files requiring administrative privileges) -type f -size +100k –> searches for files larger than 100 kilobytes in size; pipe output to | wc -l to count how many lines there are; chain together requirements -size +100k -size -5M (larger than 100 kilobytes but less than 5 megabytes, -o for the “or” option in-between sizes

Question 42

-exec // -ok (OPTIONS)

Answer 42

execute OPTION; after command –> -exec __command to execute__ {} (every file) \; (to complete execution); using -ok will ask you each time if it is “ok” to do something

Question 43

ctrl + L

Answer 43

clear the screen

Question 44

cat

Answer 44

concatenate - “stick together”; or just read contents;

Question 45

tac // rev (OPTIONS)

Answer 45

tac: reverse input; vertically – keeps lines intact across columns; rev: reverses lines horizontally – across the rows

Question 46

less

Answer 46

paging program - page through large amounts of output

Question 47

head

Answer 47

first # of lines; head -n #

Question 48

sort

Answer 48

default: sort smallest first (a-z, 0-9); sort | tac (read backwards) OR sort -r (reverse) ; SORTING NUMBERS: sort using the value number give the “n” option –> sort -n (allows the sort command to sort numerically, instead of just by the digit); SORT FOR UNIQUE RESULTS: sort -q –> only get unique results; | sort -k (KEY DEFinition use for column) #column(+any other options, such as n, r, or u with no space…use h option to sort human-readable data – h can NOT be used with n); M for month

Question 49

grep

Answer 49

search for specific text; grep ___text_to_search_for____ ; use -c option for number of lines withs specific text (grep -c __texttosearch____ ; -i option for the search to be case insensitive; -v option finds all the lines that do NOT have a certain letter/term…grep -v / –> finds all files (not directories with / in folder name) v= invert search (do the opposite)

Question 50

ls

Answer 50

ls -lF –> gives slash around directories and nothing for files

Question 51

tar

Answer 51

compress file; tar -c(create a new archive)v(verbose - don’t so this silently)f(accept files) ; tar -x(extract)vf; to create gzip file: tar -cvzf ; tar -cvjf; to extract gzip: tar -xvzf ; to extract bzip: tar -xvjf ;

Question 52

gzip // bzip

Answer 52

gzip - faster but has less compression power; gzip (archive_name.tar) –> will see .gz file extension added; gunzip (“g unzip”) to undo gzip
bzip - can compress smaller but requires more time; bzip2 –> will see bz2 file extension added (best for really large files); to undo –> bunzip2 (“b unzip 2”)

Question 53

zip

Answer 53

create zip file; zip .zip ; to undo unzip

Question 54

bash script (Bourne-Again shell script)

Answer 54

nano .sh
#!(she-bang)/bin/bash(path to interpreter - to know words are commands) (verify with “which bash” at command prompt to retrieve interpreter’s file path)
python3 to run python script (“which python3”) /usr/bin/python3
bash to run bash script

Question 55

add path to be found by running bash script in new directory

Answer 55

nano .bashrc
PATH=”$PATH:$HOME/bin” if bin is created to hold bash scripts
PATH=”$PATH:$HOME/”
new directory is now added to $PATH
*remember to make executable –> chmod +x *

Question 56

cron utility

Answer 56

crontab -e –> open crontab editor (nano)

ls -a from ~ –> hidden file with selected editor (.selected_editor) or command “select-editor”