Your linux Distro

💡 cat etc/*release that’s the path containing the version of system you are using you can use the comand cat /etc/*release : and this will output all info regardin the re

know more about your computer

find out the space ram and all info you might want

💡 free -h Gives the data in human readable
💡 cat /proc/cpuinfo Output the file containing cp infos find out the cpu info of your computer :
💡 df -h Show space across few different volumes find space on the hardrive on in your computer what we need to see is the / since that’s our main disk

To obtain informations about your hardware use

💡 sudo lshw since it give lots of info it might be great if you pass it in the less command
💡 sudo lshw | less

Alias command

alias command this is use to change or modify one command to another alias aliasname=command alias c=clear From now on clear is simply c

💡 who,whoami These commanges are used to display the user name and sometimes it displays the

💡 pwd: print the present working directory
💡 cal: used to show the calendar ,cal 2 2004 this will show the calendar of that exact month and year
💡 date: display the current date of today,date ‘+Date:%m-%y%nTime:%h:%mwho
💡 touch: used to create textfile touch name name name etc
💡 touch -c filename : avoiding creating new file if the file exists
💡 mkdir: usecd to create a directory (folder)
💡 cd :

$PATH variable displays where all the user’s program can be found

💡 echo $PATH

The cat command

who cat used to create or modify a text file with contents inside.

💡 Cat > filename
💡 cat filename to view the contents In the file , you
✅ can also use the cat command to merge different files into one .
💡 cat firstfile secondfile > the_fileyouwant_all_thosethinfgstogo
💡 cat -b filename
✅ this will print the file content with numbering in the front but will not put number on blank space but cat -n filename will
💡 cat -s file name
✅ this kinda trim all extra new lines and make them one
💡 cat > nameoffile :
✅ used to write in a file and use cat >> to append to it
💡 mv :
✅ used to rename a file or move file,mv filetorename newname

Working with directories

💡 mkdir command#command
💡 mkdir directory_name
✅ used to create or make directories mkdir file_name
💡 mkdir -p to create directory structure many direcories at the same time
💡 mkdir -p one/thow/three
/one
- /Two
  - /three

if you wanna create many directories inside of one directories simply use

💡 mkdir -p one/{one,two,three,four,five}
/one
- /two /three /four /five

Removing stuffs

💡 rmdir -option directoryname
✅ used to delete a directory
💡 rmdir directoryname
✅ delete directories which is empty
💡 rmdir -p one/two/three
✅ remove a list of direcories use -pv it’s better)
💡 rm used to remove files,to remove directories you must use rmdir or use
💡 rm -r name_of_folter
✅ delete anything on your way

cp command

💡 cp fineone filetwo this will compy contents of file one to file two and it will create the file two if it does not exist yet
💡 cp -i file_name location
✅ will be asking you if you wanna override in case there is a file with the same name on the location you are copying to
💡 cp -r folder destinatin
✅ copy a folder even if it contains something
💡 cp
✅ used to copy some files from one location to another
💡 cp filetobecopies whereuwantittogo/ifyouwantyoucangivetotheotherfileanewname
💡 ln
used to create links,soft and hark kind link, ln nameofthefileyouwannamakealinkof nameofthelink, to make a soft link you simply do
💡 ln -s
✅ whichfile whichname , soft link has a dependency on the linked file, if you delete the master then the soft link is useless
✅ you can also make links directly to a direcory ln -s Download Destop/link_to_download

less command

#command #less

💡 less name_of_file this command help you open a part of a file in terminal and allow you to go down with the arrow to see the rest and hit space to see the next page and

press B to fo on the previous page press G to brows to the end Press g to go to the beginning /keyword to search from top to bottom ?keyword search from bottom to up

file permission commands

#command #chmod

All files has permissions read and write permission etc..
the file permission read write execute has numeric values , read=4, Write=2, execute=1,

which means that the file at best can have a numerical value of 7 which is read+write+execute when you create an file in the os it has by default the read and write enabled but not the execute , means the file value is 6(read=4+write=2) (user group others) umask: umask is a system variable 0022 the first digit is not important but the 3 last are , it who one that decide a permission to a file or to older ,file=666 folder=777

Change permission

#chmod

#TO ass the execute permisison you simply use the chmod command
chmod u+x deploy.sh
#Add the execution permission to file for the user

The ls command

#command #ls ls is used to list thins in a directory, ls -l used to list things in a directory with permissions ls -l > filename : you can use the > to same output of a command inside of a file ls directory/directory : used to check contents inside of a directory without opening it

you can use _ while card to locate a specifice file ls Desktop/_.mp3 this will print all mp3 files ls name this will looks for files and document with a name in it , very handy command

ls -d */: this is a command used to list out all the directories the slash makes sure that it does not list sub directories

ls -R used to show direcories structures directories and subdirectories

ls -la :this will do a long listing

ls -lah : long listing and will actually sort the things

permissions (list files with it’s details ). and use ls -a to • -rw-rw-r— indicate that the file is a text or a pic • drwxr-xr-x indicate that the file is a document

sudo command

#command #sudo sudo command is used damn you know what it does

💡 sudo -s
✅ Enter in super user mode
💡 sudo -k
✅ exit the supersuer mode

Top command

#command #top top :this command prints out every process and everything happening in you pc and the usaage of your cpu
when in top just press s to change the refresh seconds when in top press i to filter processes when in top press k and enter the process id to kill it and press q to exit top

kill command and the ps command

#command #kill #process

💡 pidof name_of_the_process
✅ The above will give you the id of a process
💡 kill pid
✅ kill a running process ,
💡 kill -KILL pid
- 💡 kill -KILL 4355
✅ The above command is much more strong , it force the process to be closed
💡 kill -9 pid
Also a very powerful command to kill a process
💡 ps -ux
✅ Command above used to find a list of all runnig processes and their pids
💡 ps -aux
✅ Is used to see all process runneed by all users
💡 ps -U username
✅ will give you processes being runned by particular users
💡 ps -c processname
✅ list all processes of the same name

echo command

#coomand echo is used to send something back to the screen

nameofvariable=“what you want your var to hold” : you can create variables and call them when you wnat

echo $variablename :used to display contents inside of your variables

echo -e “this \t is \n”: this will just allow the use of those super characters

Uname command

#command #uname uname: this is a comand to print different informations of your computer and kernel version uname -a: to print all information

.use shortcut control d to stop modifications on a file

file commands

#command #file #wc counting words lines characters of a file

-file *:command used to display everything with their type

-wc name_of_file: command will display 3things , number of lines,words,alphhabets in your file

or you can use wc -l name_of_file,wc - name_of_file:,wc -c name_of_file:

sort command

#command #sort sort: just type this and you will know sort file_name:used to sort content in file

arguments

#sort #arguments

💡 **sort -r inputfile.txt **
sort in reverse order
💡 **sort -o filename.txt inputfile.txt **
💡 **sort filename.txt > inputfile.txt **
this will send the output of one program to another one
💡 **sort -n filename: **
this is for sorting numerically
💡 sort -nr filename:
numeric reverse sort
💡 **sort -c filename: **
check if filename is sorted
💡 sort -u filename.txt :
sort and remove duplicates

cut through files

#command #cut cut -d”your delimiter here” -f”field you want to extract” example: cut -d”-” -f”1,3” file_name

covert and copy files

#command #dd

💡 dd
✅ used to convert text form uppercase to lower case example dd if=“File you want to convert” of=“your new file” conv=ucase dd can do a lots of things from converting to extract to .

Get help

#command #man #help man: used to know about a comand man cat: will display everything about the cat command

banner : this command prints things in big using asterics eg: banner this is cool

compress command

#command #compress

💡 compress used to compress a documents
💡 compress -v filename the -v is just there to show you on how many % it converted the file if you wat to see the converted file you will have to use zcat
💡 zcat filename.z if you want to uncompress the file just use
💡 uncompress nameofthefile.z

Head and tail command

#command #head #tail head: used to display 10 first lines of a file by default ex: head daniel.txt //this will display 10 first lines you can also so something like head -n13 daniel.txt

tail:used to display 10 last lines of a file ex: tail dan.txt //will display 10 latest lines of a file tail -n3 daniel.txt //show the latest 3 lines

The pipe symbol |

#command #pipe it is used to send the output of one comand to another command

cat daniel.txt | tail -n5 | cat -n the command above will display 5lates lines of my documents numbered from 1 to 5

less command :

#command used for paginating and providing navigation command less fille.txt

zip to compress

Used to zipe files

💡 zip newzippedfilename.zip file_you_want_to_zip
💡 zip picture.zip *.png this will zip all files under the png format to a zip called picture.zip
💡 unzip picture.zip

The tar command

#command tar stand for tap archive , it also another way of grouping different files together and you can also add compression to it

tar cf mytar.tar *.png :this will group all png files together

tar cfz mytar.tar.gz myfile* : we used z to compress tar file once it is created(you can also use cfzv)

Extration

#command tar xfzv name_of_file_you_want_to_extract the which command which command is used to locate programs or executables in the system which ls which vlc which firefox etc…

Adding, modifying deleting users in Linux

#commadn #useradd #userdel #usermod

adduser command

This is the new way of adding a user, it let’s you :

useradd command

#useradd The user add command is used to add a new user to our system.

useradd -m danielerat

Added users are stored in the etc/ file, in the configuration directory

cat /etc/passwd
#output user account information
danielerat:x:1000:1000::/home/danielerat:/bin/sh
#Where
#x: means the password is stored somehwere else
#1000: is the user id
#1000: group id
#/home/danielerat : is where the home of the user is located at
#/bin/sh: the shell program the use uses when logging in

Modify the shell to use bash instead of sh

usermod -s /bin/bash danielerat
#Change the shell the user danielerat uses, his shell will now be bash

useradd mark -m -s /bin/bash -g users -c "comment"

useradd mark -m -s /bin/bash -g users -c “comment” where -m will create the default home user

where -s is the command for difault shell it allow you so use the /bin… where -g is the default group where -c is used for comment

userdel username: command used to delete a user and you must user

bashrc files .bashrcfile is a script that is executed whenever a new terminal session is started in interactive mode

super handy

view resources command

#command #df #du #free

df : display disk and space and everything you need to know df -h: display them in human readable form

du : estimate disk space used by a folder again use du -h: for human readable du -s : does the job in summary format du -s -h: even better or du -sh

du -hd1 foldername : the d1 specify one level of details and h specify human readable

free -h: used to show memory and swap stuffs

watch command

#command this command runs scripts repeatedly at a given interval watch command namew and if you wanna change the interval then do something like

watch -n 4 command : this will put the refresh to 4 seconds watch -n 1 -d command: the -d will show the thing changin

find command

#command #find used to search for files in a directory hyerarchy

💡 find -name filename will return the path of the file if it finds anything
💡 find -mtime -2 will find all files created 2days ago
💡 find -name "*.mp4*" -mtime -4 This will find all files created four days ago
💡 find directory -name filename This will look in a particulas directory a particular file name

if you wanna look in the current directory then use . and use / if you wanna start looking from the root directory

💡 find -name "[Dd]esk*"
✅ this will print everything which has desktop in it either lowercase of capitalcase d
💡 find . -name "daniel.txt"
✅ will find in the current directory a file with the name daniel
💡 find / -name passwd > text.txt
✅ this command will send all the output of the found file in the text file
💡 find / -name passwd 2> text.txt
✅ now what this will do , it will send error messages only to the text file 2 is the numeric calue for std errors

dev null path

#command #find whatever you send in the dev null path you never see them again

find / -name passwd 2> /dev/nul : here all the errors will be sent to dev null and they won’t display anymore

ls > /dev/null :nothing is gonna be displayed

dev urandom

used to generate random number

cat /dev/urandom : this will print bunch of random numbers but in the asci form

To run any application from the terminal

#command to run any app simply type the name of the app and boom firefox vlc

Use the & to run the app in the backgroun

To run the process of app in the back use & to run it in the backgorung vlc &

foreground fg

#command #fg used to get back to the program in the background

SHELL SCRIPTING

A shell scrip should have a .sh extention to run

`#` is used for commen in shell scripting

so run a shell file you simply use ./filename.sh of alternatively you can use the : sh filename.sh or bash filename.sh

positional parameter are parameter that are given when you are runing a file and they are stored in $1,$ 2 ,$3 etc..

set command

set is used to set the positional parameters set paramater1 parameter2 etc…

use echo $1 t oec h o t h e f i rs t v a r iab l eorec h o$ * to echo all the variables

read command

you read input form users by typing read then where the variable will go

you can save the parameters in a variable then on the next line set other parameters and it will be fine

count the numbers of command line arguments or parameters

echo $# : this is the command which will help you do so

if you run a file and put an _ to the end , shell will set parameter as all the files or direcory in that location sh myscript.sh _

variable

to declare a variable simply type the name= variable

a=30 b=“hello worls”

echo ” $biam$ a” //will output hello worls i am 30 echo ’ $biam$ a”’ //will output $biam$ a

Adding attributes to variables

declare -i d=123 # d is an integer declare -r e=345#e is read-only can’t be modified declare -l f=“LOLCats”#f is lolcats converted to lowercase declare -u g=“LoLCats”#g is LOLCATS

Built-in Variables

echo $HOME#return user home directory Mac:/Userc/anonymous Linux:/home/anonymous

echo $PWD#return Current directory Mac:/Userc/anonymous Linux:/home/anonymous

echo $MACHTYPE#return the machine type Mac: x86_64-apple-darwin12 Linux: x86_64-pc-linux-gnu

echo $MACHTYPE#return the system name Mac: anonymous.local Linux: anonymous

echo $BASH_VERSION#return the version of bash Mac: 3.2.48(1)-release Linux: 4.2.25(1)-release

echo $SECONDS#return the Number of seconds the bash session has run

Linux: handy for timing

echo $0#return the name of the bash Mac: 3.2.48(1)-release Linux: daniel.sh

Command substitution

how you can assign a command to a variable

d= $(pw d) ec h o$ d#now d is the same with pwd

Arithmetic

d=2 e=$((d+3))#this should be wrapped inside (()) otherwise it will not work

#you can used to incremental and dec stuff from other programming lang

((e++)) echo $e # will be incremented by one ((e+=45)) ((e*=4)) ((e/=4)) etc…

something to remember is that point of floating values have no straight representation

f= $((1/3)) ec h o$ f

Comparison operaion

expression this expression return 1 for false and 0 for true

less than [[ $a <$ b]]

greater than [[ $a >$ b]]

less than or = [[ $a <=$ b]]

greater than or = [[ $a >=$ b]]

Equal [[ $a ==$ b]]

less than [[ $a! =$ b]] NOTE THIS COMPARISONS DOES NOT WORK ON NUMBERS , TO USE COMPARISONS ON NUMBERS YOU ARE GONNA USE SOMETHING LIKE THIS:

NUMBER COMPARISON less than [[ $a - lt$ b]] greater than [[ $a - g t$ b]] less than or = [[ $a - l e$ b]] greater than or = [[ $a - g e$ b]] Equal [[ $a - e q$ b]] not than [[ $a - n e$ b]]

Logic operations logic and [[ $a &&$ b]] logic or [[ $a ∣∣$ b]] Logic not ! $b

String null values check is a string or variables is null of not is null ? [[-z $a]] i s n o t n u ll ? [[- n$ a]] example

a="" b=“cat” [[-z $a && -n$ b]] # is a null and b is not null echo $?#the ouput is 0 Which is true

String concatenation

you can do somethig like

a=“Hello” b=“world” c= $a$ b echo $c # the output will be helloworld

Size of string

echo ${#a} : you can use the # symbol before a variable name to see how long the variable is

Substring

from the examble below you can also create a substring

d=${c:2}#will start creating the string d from c 3rd ltr

echo $d # the output will be lodanie there is no hel anymore

d=${c:3:5}#choose homany characteryou want to sub to

or d=${c: -4:3} # the space must be there

String replace

replace one instence/occurence ${Yourvariable/text_you_want_to_replace/txt_u_wanna_replace_with}

replace all instences/occurences just use 2// before the one u want to replace ${Yourvariable//text_you_want_to_replace/txt_u_wanna_replace_with}

example

fruit=“apple banana banana cherry” echo ${fruit/banana/mando} output: apple mango banana cherry

echo ${fruit//banana/mando} output: apple mango mango cherry

echo ${fruit/#banana/mando} will replace the banan only if it’s in the front at first string position

echo ${fruit/%banana/mando} will replace the string only if it’s at the end of a variable

echo ${fruit/b*/mando} you can use matchings also,this will replace everything starting with b

Style text in bash

echo -e ‘\033[34;42mColor Text\033[0m’ # the -e enable the styling

-e: tell echo that we are gonna be using the escape string \033[34;42m :escape sequence where m indicate the end of it

color text :the string we wanna print out

Using tput for changin colors

flashred= $(tput setab 0; tput setaf 1; tput blink) #mark the erro.. red=$ (tput setb 0; tput setaf 4)#mar the colos os somet… none= $(tput sgr0) #marks the end of the styling echo -e$ flashred “ERROR:“# $n o n e$ red”Something went wrong”$none

printf command

printf is used just as the echo command but with more functionalities

ex

printf “Name:\t%s\nID:\t%04d\n” “Ilunga gisa” “23”

Names: \t:tabulation %s:string_holder \n:startnewline ID: \t:tabulation %04d:digit_holder_with_4dgts

TR COMMAND

Tr simply translate text

tr option1 option2 :where option one is text you want to translate and option2 is text you want to translate it to

echo my foot is great | tr o x#the output will be my fxxt is great it converted all teh o to x

echo my foot is great | tr mo ya :here m—>y and o—>a

echo footbar | tr {:lower:} {:upper:} :will translate all text from lowercase to uppercase

array

to declare an array it’f fairly easy

a=(“apple” “banana” “avocado” “pineaple”) echo ${a[2]}#will output avocado

b+=(“mango”)#this will append at the end of line

echo ${b[@]}#this is used to print out whole data within an array

echo ${[@]: -1} will print the last element of an array

associative arrays only works in bash 3 and above

declare -A myarr myarr[color]=blue myarr[“name”]=“ilunga gisa daniel” echo “My name is ” $m y a rr [nam e] an d m yco l or i s$ {myarr[color]}

if statement

can be written in many form :

if [ expression ] or if expression

or can contain in double paranthesis for integer comparison if (( expression ))

or can have no brackets at all if expression

AND whatever the comparison you are doing you can continue the if

either with: if expression;then

or with: if expression then echo “things to be done when expression is true elif expression2;then echo “second condition” else echo “what will be done if the expressions are false fi#this is simply there to close an if statement

Script Example

#!/bin/bash #A program to print lots of info in your computer

color= $(tp u t se t ab 1) e n d =$ (tput sgr0) a=5 if [ $a - g t 4]; t h e n ec h o$ a is greater than 4! else echo ” $ai s$ color not $end greater than 4!” fi

#we use the for regular expressions b=“we are the face of the world” #this regular expression check if there is an int in the a variable if [[ $a =~ [0-9]+]] then

if it finds a numebr

echo “there is indeed a number in this string” else echo “There is no numebr in this string sir” fi

While loop

i=0 while [ $i - l e 10]; d oec h o i :$ i ((i+=2)) done

ultil loop

j=0 until [ $j - g e 10]; d oec h o j :$ j ((j++)) done

for loop

for i in 1 2 3 do echo $i done //the output will be 1 2 3

it you wanna check from a large range , do something like for i in {1…100} #you can specify intervals also , {1..100..2}, will count by 2 do echo $i done

There is another variation of ForLoop statement which works exactly like that one above

for(( i=1; i<=10; i++ )) do echo $i done

Looping through an array

You can also look through an array also with:

arr=(“apple” “banana” “avocado” “pineaple”) for i in $a rr [@] d oec h o$ i done

ar=(“apple” “banana” “avocado” “pineaple”) for (( i=0; i<=3; i++ )) do echo ${ar[$ i]} done

Looping in an associative array

declare -A arr

arr[“name”]=“ilunga gisa daniel” arr[“age”]=“23”

for i in ” $! a rr [@] " d oec h o "$ i: ${arr[$ i]}” #above $ib ec am e ak ey an d t o a ccess t h e v a l u es w e u se d$ {arr[$i]} done

You can also use command substituion in the for loop

it would look like this : for i in $(ls) …

Case Statement

a=“dog”

case $a in cat) echo “Feline”;; #test if the variable a has cat in it and display feline if true jad) echo “Item”;; #those ;; are there to indicate the ending of the case dog|puppy) echo “Canine”;; #we used the | to sppecify a list of things to match … *) echo “No possible match”;; #the statement above is alike the default in other languages

esac #statement above closes the case statement

Function

To declare a funtion in bash you simply type

function Funtion_name{ echo “whatever you want your funtion to be doing”; }

to call the funtion simply type its name

Funtion_name

Argumented funtion

funtion greetings { echo “Hi, $1” #the one above is an argument , }

#call our funtion with an argument looks like this

greetings Daniel #output will be , Hi, Daniel

#simple example of the if statement echo “Please type a name of a file ” read s t if mv $s$ t then echo “You file was renamed fine” fi

if else statemetn

if [ $num -lt 10 ]#this state ment check that num variable is less than or equal to 10 if [$ num -gt 10 ] for greater than or equal example of program

echo “Enter a number between 10 and 20” read num if [ $n u m - lt 10] t h e n ec h o " t h e n u mb er i s l ess t han 10" e l i f [$ num -gt 20 ] then echo “Number is greater than 20” else echo “The number is between 10 and 20” fi

Flags in shell

while getopts u:p: option; do case $o pt i o nin u) u ser =$ OPTARG;; p) pass=$OPTARG;; esac done

echo “User: $u ser / P a ss :$ pass”

#while executing the program we are gonna call it with those flags #and their values

./file.sh -u Danielerat -p woldword

ouput

“User: Danielerat / Pass: woldword

you can also check wether a flag was added simply do not use the : after the flag name

while getopts :u:p:abc option; do case $o pt i o nin u) u ser =$ OPTARG;; p) pass= $OPT A RG;; a) ec h o " T h e a f l a g w a s a dd e d " b) ec h o " T h e b f l a g w a s a dd e d " c) ec h o " T h ec f l a g w a s a dd e d " ?) ec h o " I d o n^{'} t kn o w ab o u tt ha t f l a g$ OPTARG;; esac done

./file.sh -a -b -c

output:

the a flag was added the b flag was added the c flag was added User: anonymous / Pass: we are legion

and notice that we have used : before u , and used ? in our case statement , this is for capturing any other non specified tag

#if we try to call with -z flag it will show the ? echo

./file.sh -az

The a flag was added I don’t think i know about that z flag User: anonymous / Pass: we are legion

Reading user’s data

echo “What is your name? ” read name

echo “What is your password?” read -s pass #use the -s when you want the input to be silent aka not show on the screen while user is typing

read -p “what is your favorite animal ” animal

use -p when you want input to be entered on the same line

#we can also combine -p and -s read -p “what is your favorite animal ” -s animal

echo “Name: $nam e, P a ss :$ pass ,animal: $animal

read -p “[sudo] password fo $U SER : " - s anima l ec h o " N am e :$ name, Pass: $p a ss, anima l :$ animal”

Get user’s data using select

select variablename in “list” “of things” “to” “select” “in” do echo “You selected $animal!” break#breaking the loop so that it can not run forever

done

example 0000000

select animal in “cat” “dog” “cow” do echo “you selected $animal” break done

combined with a case

echo “Choose your favorite animal ? ” select option in “cat” “dog” “cow” “snake” “quit” do case $option in cat) echo “Cats like to sleep.”;; dog) echo “Dogs are brest Human friends.”;; cow) echo “Cow gives a good milk for sure”;; snake) echo “Snames are way too annoying.”; break;; quit) break;; *) echo “Can you please make a sane choice ?” esac done

Error tolerance in a script

Check readed data

read -p “What is your name? ” a #read the input of the user while -z $a #-z will check for null status do read -p “I need your name please: ” a #is it’s null then read prompt is printed out again done

echo “You are called $a” # in case the condition is false this execute

There is some case where you want to put a default value in case user does not select anything

read -p “What is your name? [john doe]” a #read the input of the user while -z $a #-z will check for null status do a=“john Doe” #In this case we innitialize the a variable to be john doe

done

echo “You are called $a” # in case the condition is false this execute

while with regular expressions

if [ $# -lt 3 ]; then cat <<- EOM this command required 3 agruments username ,user id, and favorite number EOM

else echo “username: $1" ec h o " u ser I d :$ 2” echo “fav num: $3”

fi#closing the if statement

expr tool

the expr tool help us perform mathmatical operations easily and it works only with integer values #example of how the expr tool works a=43 b=17 expr $a +$ b expr $a -$ b expr $a \*$ b echo expr $a / $b echo $a$ b=expr $a % $b

when dealing with operators you must put space between the variablea and the operator and again what you have to do when you want to use * or () in you ccoding you have to escape them os course with the back slash

bc command

in alternative you can use the bc command which works well with floating points and all sorts of variable for reference use the code below

a=36.2 b=5.4342 c=echo $a + $b | bc #not that there is no space between = and `echo… echo $cec h o$ a * $b ∣ b cec h o$ a / $b

change the echo printing style

in order to instruct echo we have to use escape sequences

\n : for new line

\r :used to gnore text in front of it echo “WE are not the \r leaders of the toilet” the output will be leaders of the toilets

\t :horizontal tab

\b :ommit a character backward echo “Daniel is\b cool” output will be Daniel i cool

\033[1m :used to put a statement in bold to go back in normal mode you will use \033[0m

you can use 1,2,3,4…9 \033[1m , \033[2m ,\033[3m …\033[9m and they all have different patters

the tput command

tput clear: used to clear the terminal tput lines : display the total # rows on screen

tput cols:show the numbers of columns tput cup 12 30 : put the mouse cursor on row 12 column 20 tput bold: put text in bold

the echo $? command

that command above is used if you want to check that a particular command did execute or not it return 0 if a command was executed and 1 if it was not executed ex: mkdir dfe ; this must return 0 if you run echo $? after executing it

if statement

#simple example of the if statement echo “Please type a name of a file ” read s t if mv $s$ t then echo “You file was renamed fine” fi

if else statemetn

if [ $num -lt 10 ]#this state ment check that num variable is less than or equal to 10 if [$ num -gt 10 ] for greater than or equal example of program

-lt:less than -gt:greater tan -eq:equal -ne: not equal to -le: less than or equal -greater than or equal -f check if file exist [ -f filename]

checking files in shell scripting

we are gonna use the -f to find the files echo “Enter a file name” read name if [ -f $name ] #use -d if you want to find a directory -c for character special files -x execute permission #-b images or video files -r if you have read permissin -w if you have write permission -s if your file is greater than 0 aka empty then echo “we did find the file” else echo “we did not find the file” fi

INFINITE SKILLS LEARN UBUNUT TRAINING

sudo apt-get upgrade

command used to check for packages that are out of dat and update them

sudo apt-get install packagename

used to install softwared or packages

sudo apt-get install emacs vlc postfix : this command will install those different things in the computer

uninstall applications

sudo apt-get remove packagename

or you can use autoremove to remove packages you nolonger use

sudo apt-get autoremove

this remove all packages that you are nolonger using

services management

services are programs that runs in the background

sudo service —status-all :check all the scripts and their status

to start a service simply write: sudo service servicename start

Process management

a process is a running instance of a program

ps -u: list all running process

ps a : used to show list of all processes that are running ps eaf : also works like ps a but it brings some additional info ps aux :show all porcess running no matter the user you are running as ps aux | grep firefox : this is used to narrow the list , it looks for a particular program

top:to bring the list of program which is constantly upgrading we are gonna use top

killing a process:

kill processid:kill a process by it’s id killall processName kill a process by its name

killall -9 firefox:the -9 kill a process no matter what’s happening

Grep and sed command

#command #grep #sed Grep Global Regular Expression Print command is used to search for text. can be used to search for file of string partten

💡 grep word_to_search_for your_file

grop tree "My foe outstretched beneath the tree."
#output
My foe outstretched beneath the "tree".

Structure looks like this

💡 grep [options] pattern [files]

Options Description

💡 c : This prints only a count of the lines that match a pattern
r : Search in a directory and sub directory recursively
💡 h : Display the matched lines, but do not display the filenames.
💡 i : Ignores, case for matching
💡 l : Displays list of a filenames only.
💡 n : Display the matched lines and their line numbers.
💡 v : This prints out all the lines that do not matches the pattern
💡 e exp : Specifies expression with this option. Can use multiple times.
💡 f : Takes patterns from file, one per line.
💡 E : Treats pattern as an extended regular expression (ERE)
💡 w : Match whole word
💡 o : Print only the matched parts of a matching line, with each such part on a separate output line.

example

grep -in "the" poem.txt
#n for new line,i for ignone case sensi..
 
grep -i the poem.txt fish.txt
#n find for the word the in those two specifi files
 
grep -vi "the" poem.txt
#will output all lines exept those with the inside of them
 
grep -i -r "the" Desktop
#Search for directory and subdirectory recursively
 
$grep –e "Agarwal" –e "Aggarwal" –e "Agrawal" geekfile.txt
# multiple expression at the same time

grep -E :used with regular expressions

grep -E "[hijk]" poem.txt
# lines containing characters hijk
 
grep -E "\w{6,}" poem.txt
# will print lines with 6chars or longer
 
grep "^unix" geekfile.txt
# unix should be at the beginnig of the line to be outputed
grep "os$" geekfile.txt
# os should be at the end of the line
 
grep -A 5 disk
# will print 5 lines after a match in our case it's disk

SED

sed OPTIONS… [SCRIPT] [INPUTFILE…] we use the sed comman to change one thing to another

sed ‘s/unix/linux/’ geekfile.txt //will replace all the occurence of the word unix by linux form the file geekfile

/n where n=anu number sed ‘s/unix/linux/2’ geekfile.txt // will replace the number of occurrences

Replace from nth occurrence $sed ‘s/unix/linux/3g’ geekfile.txt

echo “Welcome To The Geek Stuff” | sed ‘s/(\b[A-Z])/(\1)/g’ (W)elcome (T)o (T)he (G)eek (S)tuff

sed -n ‘s/unix/linux/p’ geekfile.txt //print only the replaced lines

sed ‘1,3 s/unix/linux/’ geekfile.txt replace strings in a range of line

deleting lines from a particular file sed ‘nd’ filename.txt sed ‘5d’ filename.txt

cat fileNmae | sed ‘s/daniel/gisa/’ : this program will find in the file everywhere it’s written daniel and change it to gisa

sed ‘s/daniel/gisa/g’ use the g to replace globaly instead of once on a line

Add a user to a particulas group

here is the parameters to put a user to a group sudo useradd -d /home/anonymous -s /bin/bash -g staff -m anonymous

use cron to automate tasks

sudo visudo :this is a file that contain settings for our sudo

if you want password to be prompted to you or any other thing regarding sudo then you can find it in there

use sudo rm -RF * : this command will erase everything on your system

Networking in UBuntu

ifconfig :see all interface on your computer ifconfig enp2s0 : show configurations of that particular interface

Looking at DNS informations

host www.google.com : this will give you the informations about that domain , ipaddress included

you can also use:

nslookup www.google.com

also used as host

dig www.mysite.com

also used as nslookup but with lots of details

so all the 3 are used for ipaddresses

changing Nameservers

changing Dns server you are pointing to: typicaly you have a local dns server (airtel server)

cat /etc/resolv.conf :here is the place where name servers are stored

watch video 06_03

Basic troubleshooting

ping 4.2.2.1 or ping www.lynda.com

traceroute 4.2.2.1

address resoution protocol

arp -a :show the arp table rooute netstat -rn netstat -an

netstat -an | less : used to see your web trafic

communicate with a host

step 1: create my own server nc -l -p 8000 step 2:connect to the localhost nc localhost 8000

RECOVER LOST DATA FROM A USB FLAS IN UBUNTU

step one: sudo apt-get install testdisk

step two: sudo photorec

then follow the instruction

Ubuntu Tips

bash expension fills things your you let’s say you want to creat 100files , instead of typing all of em out just type : touch file_{1..100}.txt

mkdir folder_{1..20}/{a..z}#will create 20folders and add a-z folders in ead

Commmand substitution

if you do date , it will print the date

but if you do echo date -hello there , it will not print the date so to substitute one command in another one use

echo $(date) - Hello from script

Alias and Unalias

alias o=echo now o is exaclty the same as echo

Curl

Used to send and recieve data on different protocols means it can send and download data frorm terminal

curl url -o filename

or you can use -O to five file the default download name

WGET

Also used for downloading stuffs but is much more tollerent to errors and much better according to daniel

use the command :wget url let’s say the downlooad it interrupted ,well no trouble for wget you can continue the download with wget url -c , this will continue form where the download broke from

SSH REMOTE ACCESS

first install openssh-server on the computer you want to access remotely

sudo apt install openssh-server

2.check the status of ssh connections if it’s running or nor systemctl status sshd if it is not running we can use “systemctl start sshd” to start the server

3.The 3rd thing to check is to see if the firewall is allowing trafic to the ssh firewall(by default it runs on port 22 )

Let’s take a loook at the firewall with “sudo ufw status” it is inactive

we need to add a rule to allow port 22 access we can do that with -sudo ufw allow 22/tcp after allowing we need to restart the firewall with: -sudo systemctl restart ufw
Now let’s enable the firewall with: -sudo ufw enable Options Description -c : This prints only a count of the lines that match a pattern -h : Display the matched lines, but do not display the filenames. -i : Ignores, case for matching -l : Displays list of a filenames only. -n : Display the matched lines and their line numbers. -v : This prints out all the lines that do not matches the pattern -e exp : Specifies expression with this option. Can use multiple times. -f file : Takes patterns from file, one per line. -E : Treats pattern as an extended regular expression (ERE) -w : Match whole word -o : Print only the matched parts of a matching line, with each such part on a separate output line.

@danielerat My Learning ©2023📚

Development🚀

Development🚀

Linux Shell

Your linux Distro §

know more about your computer §

find out the space ram and all info you might want §

Alias command §

The cat command §

Working with directories §

Removing stuffs §

cp command §

less command §

file permission commands §

Change permission §

The ls command §

sudo command §

Top command §

kill command and the ps command §

echo command §

Uname command §

file commands §

sort command §

arguments §

cut through files §

covert and copy files §

Get help §

compress command §

Head and tail command §

The pipe symbol | §

less command : §

zip to compress §

The tar command §

Extration §

Adding, modifying deleting users in Linux §

adduser command §

useradd command §

Modify the shell to use bash instead of sh §

view resources command §

watch command §

find command §

dev null path §

To run any application from the terminal §

Use the & to run the app in the backgroun §

foreground fg §

SHELL SCRIPTING §

# is used for commen in shell scripting §

set command §

read command §

count the numbers of command line arguments or parameters §

variable §

Adding attributes to variables §

Built-in Variables §

Command substitution §

Arithmetic §

Comparison operaion §

String null values check is a string or variables is null of not is null ? [[-z a]]isnotnull?[[−na]] example §

String concatenation §

you can do somethig like §

Size of string §

Substring §

String replace §

example §

Style text in bash §

Using tput for changin colors §

printf command §

ex §

TR COMMAND §

array §

associative arrays only works in bash 3 and above §

if statement §

if it finds a numebr §

While loop §

ultil loop §

for loop §

Looping through an array §

Looping in an associative array §

You can also use command substituion in the for loop §

Case Statement §

Function §

Your linux Distro

know more about your computer

find out the space ram and all info you might want

Alias command

The cat command

Working with directories

Removing stuffs

cp command

less command

file permission commands

Change permission

The ls command

sudo command

Top command

kill command and the ps command

echo command

Uname command

file commands

sort command

arguments

cut through files

covert and copy files

Get help

compress command

Head and tail command

The pipe symbol |

less command :

zip to compress

The tar command

Extration

Adding, modifying deleting users in Linux

adduser command

useradd command

Modify the shell to use bash instead of sh

view resources command

watch command

find command

dev null path

To run any application from the terminal

Use the & to run the app in the backgroun

foreground fg

SHELL SCRIPTING

`#` is used for commen in shell scripting

set command

read command

count the numbers of command line arguments or parameters

variable

Adding attributes to variables

Built-in Variables

Command substitution

Arithmetic

Comparison operaion

String null values check is a string or variables is null of not is null ? [[-z $a]] i s n o t n u ll ? [[- n$ a]] example

String concatenation

you can do somethig like

Size of string

Substring

String replace

example

Style text in bash

Using tput for changin colors

printf command

ex

TR COMMAND

array

associative arrays only works in bash 3 and above

if statement

if it finds a numebr

While loop

ultil loop

for loop

Looping through an array

Looping in an associative array

You can also use command substituion in the for loop

Case Statement

Function

to call the funtion simply type its name

Argumented funtion

if else statemetn

Flags in shell