Hoisting :
we can use variable before creating
message = “hello” // without creating variable
console.log(message);
var message; // this type of declaration is hoisting type in JavaScript.
// Hoisting
Login
/ Hoisting
function codeHoist(){
a = 10;
let b = 50;
}
codeHoist();
console.log(a); //10
console.log(b); //Reference Error b is not defined
JavaScript is a versatile programming language primarily used to create dynamic and interactive features on websites.
JavaScript is a scripting language that allows you to implement complex features on web pages.
Browsers have Interpreters. It will converts JAVASCRIPT code to machine code.
Browsers have its own interpreters like
JavaScript- Identifiers :
var message; –> Variable (Identifier)
message = ‘Javascript’;
func sayHello() {
console.log(‘Hello’)
}
//sayHello Is the identifier for this function.
//variables , objects,functions,arrays ,classes names are identifiers in js.
SCOPE :
In JavaScript, scope refers to the context in which variables and functions are accessible. It determines the visibility and lifetime of these variables and functions within your code. There are three main types of scope in JavaScript.
Global Scope:.
example :
let globalVar = "I'm global";
function test() {
console.log(globalVar); // Accessible here
}
test();
console.log(globalVar); // Accessible here too
Function Scope
example :
function test() {
let localVar = "I'm local";
console.log(localVar); // Accessible here
}
test();
console.log(localVar); // Error: localVar is not defined
Block Scope:
let or const within a block (e.g., inside {}) are only accessible within that blockexample :
{
let blockVar = "I'm block-scoped";
console.log(blockVar); // Accessible here
}
console.log(blockVar); // Error: blockVar is not defined
Keywords | Reserved Words
Keywords are reserved words in JavaScript that cannot use to indicate variable labels or function names.
Variables
variables ==> stored values ==> it will stored to ram / It will create separate memory.so we need memory address for access the values.
Stores Anything :
JavaScript will store any value in the variable.
Declaring Variable :
* Var * let * const
we can declare variable using above keywords:
Initialize Variable :
Using assignment operator to assign the value to the variables. var text = "hello";
Hoisting :
we can use variable before creating
message = “hello” // without creating variable
console.log(message);
var message; // this type of declaration is hoisting type in JavaScript.
// Hoisting
/ Hoisting
function codeHoist(){
a = 10;
let b = 50;
}
codeHoist();
console.log(a); //10
console.log(b); //Reference Error b is not definedJavaScript is a versatile programming language primarily used to create dynamic and interactive features on websites.
JavaScript is a scripting language that allows you to implement complex features on web pages.
Browsers have Interpreters. It will converts JAVASCRIPT code to machine code.
Browsers have its own interpreters like
JavaScript- Identifiers :
var message; –> Variable (Identifier)
message = ‘Javascript’;
func sayHello() {
console.log(‘Hello’)
}
//sayHello Is the identifier for this function.
//variables , objects,functions,arrays ,classes names are identifiers in js.
SCOPE :
In JavaScript, scope refers to the context in which variables and functions are accessible. It determines the visibility and lifetime of these variables and functions within your code. There are three main types of scope in JavaScript.
Global Scope:.
example :
let globalVar = "I'm global";
function test() {
console.log(globalVar); // Accessible here
}
test();
console.log(globalVar); // Accessible here too
Function Scope
example :
function test() {
let localVar = "I'm local";
console.log(localVar); // Accessible here
}
test();
console.log(localVar); // Error: localVar is not defined
Block Scope:
let or const within a block (e.g., inside {}) are only accessible within that blockexample :
{
let blockVar = "I'm block-scoped";
console.log(blockVar); // Accessible here
}
console.log(blockVar); // Error: blockVar is not defined
Keywords | Reserved Words
Keywords are reserved words in JavaScript that cannot use to indicate variable labels or function names.
Variables
variables ==> stored values ==> it will stored to ram / It will create separate memory.so we need memory address for access the values.
Stores Anything :
JavaScript will store any value in the variable.
Declaring Variable :
* Var * let * const
we can declare variable using above keywords:
Initialize Variable :
Using assignment operator to assign the value to the variables. var text = "hello";
Understanding Routes
React- Router is used for render the components depends on URL without reloading the browser page. It navigates a page to another page without page reloads. we can use router in react project, first we install the react-router-dom package from react.
Then, access the router using
import {BrowserRouter,Router,Routes} from 'react-router-dom';
after that we use link to diplay the browser using Link instead <a href=''> in react.
so,
import {BrowserRouter,Router,Routes,Link} from ‘react-router-dom’;
example for using Link and routes:
Using Links:
'/' is the root page it display default home page
<Link to='/'>Home</Link>
<Link to='/about'>About</Link>
<Link to='/contact'>Contact</Link>
}/> }> }/>
Using Routes:
<Browser Router>
<Router>
<Routes path='/' element={<Home/>}/>
<Routes path='/about' element={<About/>}>
<Routes path='/contact' element={<Contact/>}/>
</Router>
</Browser Router>
Understanding Routes
React- Router is used for render the components depends on URL without reloading the browser page. It navigates a page to another page without page reloads. we can use router in react project, first we install the react-router-dom package from react.
Then, access the router using
import {BrowserRouter,Router,Routes} from 'react-router-dom';
after that we use link to diplay the browser using Link instead <a href=''> in react.
so,
import {BrowserRouter,Router,Routes,Link} from ‘react-router-dom’;
example for using Link and routes:
Using Links:
'/' is the root page it display default home page
<Link to='/'>Home</Link>
<Link to='/about'>About</Link>
<Link to='/contact'>Contact</Link>
}/> }> }/>
Using Routes:
<Browser Router>
<Router>
<Routes path='/' element={<Home/>}/>
<Routes path='/about' element={<About/>}>
<Routes path='/contact' element={<Contact/>}/>
</Router>
</Browser Router>
sudo apt install -y postgresql-common
sudo /usr/share/postgresql-common/pgdg/apt.postgresql.org.sh
To manually configure the Apt repository, follow these steps:
sudo apt install curl ca-certificates
sudo install -d /usr/share/postgresql-common/pgdg
sudo curl -o /usr/share/postgresql-common/pgdg/apt.postgresql.org.asc –fail https://www.postgresql.org/media/keys/ACCC4CF8.asc
sudo sh -c ‘echo “deb
[signed-by=/usr/share/postgresql-common/pgdg/apt.postgresql.org.asc]
https://apt.postgresql.org/pub/repos/apt $(lsb_release -cs)-pgdg main” > /etc/apt/sources.list.d/pgdg.list’
sudo apt update
sudo apt -y install postgresql
sudo -i -u postgres
psql
\q
createdb my_pgdb
psql -d my_pgdb
\conninfo
After the we have download pgadmin using cmd :
#
# Setup the repository
#
# Install the public key for the repository (if not done previously):
curl -fsS https://www.pgadmin.org/static/packages_pgadmin_org.pub | sudo gpg --dearmor -o /usr/share/keyrings/packages-pgadmin-org.gpg
# Create the repository configuration file:
sudo sh -c 'echo "deb [signed-by=/usr/share/keyrings/packages-pgadmin-org.gpg] https://ftp.postgresql.org/pub/pgadmin/pgadmin4/apt/$(lsb_release -cs) pgadmin4 main" > /etc/apt/sources.list.d/pgadmin4.list && apt update'
#
# Install pgAdmin
#
# Install for both desktop and web modes:
sudo apt install pgadmin4
# Install for desktop mode only:
sudo apt install pgadmin4-desktop
# Install for web mode only:
sudo apt install pgadmin4-web
# Configure the webserver, if you installed pgadmin4-web:
sudo /usr/pgadmin4/bin/setup-web.sh
After tat setting password for pgadmin
sudo -i -u postgres
psql
\password postgres
Enter new pasword :
Enter it again
Reference : https://www.postgresql.org/download/linux/ubuntu/
https://www.pgadmin.org/download/pgadmin-4-apt/
sudo apt install -y postgresql-common
sudo /usr/share/postgresql-common/pgdg/apt.postgresql.org.sh
To manually configure the Apt repository, follow these steps:
sudo apt install curl ca-certificates
sudo install -d /usr/share/postgresql-common/pgdg
sudo curl -o /usr/share/postgresql-common/pgdg/apt.postgresql.org.asc –fail https://www.postgresql.org/media/keys/ACCC4CF8.asc
sudo sh -c ‘echo “deb
[signed-by=/usr/share/postgresql-common/pgdg/apt.postgresql.org.asc]
https://apt.postgresql.org/pub/repos/apt $(lsb_release -cs)-pgdg main” > /etc/apt/sources.list.d/pgdg.list’
sudo apt update
sudo apt -y install postgresql
sudo -i -u postgres
psql
\q
createdb my_pgdb
psql -d my_pgdb
\conninfo
After the we have download pgadmin using cmd :
#
# Setup the repository
#
# Install the public key for the repository (if not done previously):
curl -fsS https://www.pgadmin.org/static/packages_pgadmin_org.pub | sudo gpg --dearmor -o /usr/share/keyrings/packages-pgadmin-org.gpg
# Create the repository configuration file:
sudo sh -c 'echo "deb [signed-by=/usr/share/keyrings/packages-pgadmin-org.gpg] https://ftp.postgresql.org/pub/pgadmin/pgadmin4/apt/$(lsb_release -cs) pgadmin4 main" > /etc/apt/sources.list.d/pgadmin4.list && apt update'
#
# Install pgAdmin
#
# Install for both desktop and web modes:
sudo apt install pgadmin4
# Install for desktop mode only:
sudo apt install pgadmin4-desktop
# Install for web mode only:
sudo apt install pgadmin4-web
# Configure the webserver, if you installed pgadmin4-web:
sudo /usr/pgadmin4/bin/setup-web.sh
After tat setting password for pgadmin
sudo -i -u postgres
psql
\password postgres
Enter new pasword :
Enter it again
Reference : https://www.postgresql.org/download/linux/ubuntu/
https://www.pgadmin.org/download/pgadmin-4-apt/
Solution:
sudo fsck /dev/sda2
sudo ntfsfix /dev/sda2
sudo ntfsfix -d /dev/sda2
Solution:
sudo fsck /dev/sda2
sudo ntfsfix /dev/sda2
sudo ntfsfix -d /dev/sda2
I’m experiencing an issue with Eclipse where it closes automatically when I use ‘System.out.println’.
Environment :
Eclipse Version: eclipse 2024-03 is the latest version of Eclipse today I reinstalled it.
I downloaded Eclipse from the official Eclipse Foundation website at Eclipse Downloads | The Eclipse Foundation 1.
JDK version : java 22.0.1 2024-04-16
Java SE Runtime Environment (build 22.0.1+8-16)
Java HotSpot 64-Bit Server VM (build 22.0.1+8-16, mixed mode, sharing)
Operating System: Ubuntu Ubuntu 22.04.4 LTS
Problem Description: Whenever I run a simple Java program that uses System.out.println. Eclipse hung and closed automatically without getting any error messages.
How i fix this issue
I fix this issue
Hi everyone,
I recently encountered a problem with Eclipse. when I upgraded Ubuntu 20 to Ubuntu 22 then some applications did not work properly . After some troubleshooting, I discovered that switching from Wayland to X11 resolved the issue. Here’s how you can do it:
How to Switch from Wayland to X11 on Ubuntu
If you’re experiencing issues with Wayland and want to switch back to X11, follow these steps:
Turn off Wayland and switch back to X11.
- Log out of Ubuntu.
- Start to log in again and click the icon that has appeared at the bottom right of the screen – that gives you the option to disable Wayland.
- Switch back to Xorg.
Switching to X11 fixed the issues I was having, so I hope this helps anyone experiencing similar problems. Let me know if you have any questions or need further assistance!
I’m experiencing an issue with Eclipse where it closes automatically when I use ‘System.out.println’.
Environment :
Eclipse Version: eclipse 2024-03 is the latest version of Eclipse today I reinstalled it.
I downloaded Eclipse from the official Eclipse Foundation website at Eclipse Downloads | The Eclipse Foundation 1.
JDK version : java 22.0.1 2024-04-16
Java SE Runtime Environment (build 22.0.1+8-16)
Java HotSpot 64-Bit Server VM (build 22.0.1+8-16, mixed mode, sharing)
Operating System: Ubuntu Ubuntu 22.04.4 LTS
Problem Description: Whenever I run a simple Java program that uses System.out.println. Eclipse hung and closed automatically without getting any error messages.
How i fix this issue
I fix this issue
Hi everyone,
I recently encountered a problem with Eclipse. when I upgraded Ubuntu 20 to Ubuntu 22 then some applications did not work properly . After some troubleshooting, I discovered that switching from Wayland to X11 resolved the issue. Here’s how you can do it:
How to Switch from Wayland to X11 on Ubuntu
If you’re experiencing issues with Wayland and want to switch back to X11, follow these steps:
Turn off Wayland and switch back to X11.
- Log out of Ubuntu.
- Start to log in again and click the icon that has appeared at the bottom right of the screen – that gives you the option to disable Wayland.
- Switch back to Xorg.
Switching to X11 fixed the issues I was having, so I hope this helps anyone experiencing similar problems. Let me know if you have any questions or need further assistance!
sudo apt-get update
sudo apt-get -y install openboard
OpenBoard is an open source cross-platform interactive whiteboardapplication designed primarily for use in schools.
To remove obenboard
sudo apt-get remove openboard
sudo apt-get -y autoremove openboard
Reference: https://installati.one/install-openboard-ubuntu-22-04/
sudo apt-get update
sudo apt-get -y install openboard
OpenBoard is an open source cross-platform interactive whiteboardapplication designed primarily for use in schools.
To remove obenboard
sudo apt-get remove openboard
sudo apt-get -y autoremove openboard
Reference: https://installati.one/install-openboard-ubuntu-22-04/
class Shop
{
static String shopName ="Updatez";
int price, discount; // non-static variable
public static void main(String args[])
{
Shop product = new Shop();
product.price =1000;
product.discount =10;
s.sell(); // method calling
}
void sell()
{
int discount = 30; // local variable
System.out.println(discount);30
System.out.println(this.price);
System.out.println(this.discount);
}
}
output:
30
1000
10
we cannot use this keyword inside the static method and also a main method
import java.util.Scanner;
Scanner sc = new Scanner(System.in);
A simple text scanner that can parse primitive types and strings using regular expressions.
A Scanner breaks its input into tokens using a delimiter pattern, which by default matches whitespace. The resulting tokens may then be converted into values of different types using the various next methods.
Scanner sc = new Scanner(System.in);
System.out.println("Enter the value:");
int value =sc.nextInt();
System.out.println(value);
reference:https://docs.oracle.com/javase/8/docs/api/java/util/Scanner.html
Fields are categorized by various data types in java.
Methods -> set of Instructions with a name for a specific task.
Data types in java :
Java programming language is statically typed, means all variables must first be declared before being used.
Primitive Data types in java :
Field is a data member of a class. Unless specified otherwise, a field is not static.
Static variables:
static String owner_name ="Elavarasu";
Non-static variables: | Instance [object specific]
String employee = "name";
Source-Code:
Reference : https://www.shiksha.com/online-courses/articles/data-types-in-java-primitive-and-non-primitive-data-types/
class Shop
{
static String shopName ="Updatez";
int price, discount; // non-static variable
public static void main(String args[])
{
Shop product = new Shop();
product.price =1000;
product.discount =10;
s.sell(); // method calling
}
void sell()
{
int discount = 30; // local variable
System.out.println(discount);30
System.out.println(this.price);
System.out.println(this.discount);
}
}
output:
30
1000
10
we cannot use this keyword inside the static method and also a main method
import java.util.Scanner;
Scanner sc = new Scanner(System.in);
A simple text scanner that can parse primitive types and strings using regular expressions.
A Scanner breaks its input into tokens using a delimiter pattern, which by default matches whitespace. The resulting tokens may then be converted into values of different types using the various next methods.
Scanner sc = new Scanner(System.in);
System.out.println("Enter the value:");
int value =sc.nextInt();
System.out.println(value);
reference:https://docs.oracle.com/javase/8/docs/api/java/util/Scanner.html
Fields are categorized by various data types in java.
Methods -> set of Instructions with a name for a specific task.
Data types in java :
Java programming language is statically typed, means all variables must first be declared before being used.
Primitive Data types in java :
Field is a data member of a class. Unless specified otherwise, a field is not static.
Static variables:
static String owner_name ="Elavarasu";
Non-static variables: | Instance [object specific]
String employee = "name";
Source-Code:
Reference : https://www.shiksha.com/online-courses/articles/data-types-in-java-primitive-and-non-primitive-data-types/
1. Java is simple:
Java is a simple programming language. Because syntax is derived from C & C++ language. Java has removed some complex topics like Pointers, Operator Overloading, and Multiple Inheritance explicit memory allocation. Java has an Automatic Garbage Collection.
2. Java is Robust :
3. Java is Platform Independent :
Operating System – Os is interface between Human Being and Machine. Platform is nothing but Processor + Os .
Reference :
https://www.geeksforgeeks.org/java
https://www.javatpoint.com/features-of-java
1. Java is simple:
Java is a simple programming language. Because syntax is derived from C & C++ language. Java has removed some complex topics like Pointers, Operator Overloading, and Multiple Inheritance explicit memory allocation. Java has an Automatic Garbage Collection.
2. Java is Robust :
3. Java is Platform Independent :
Operating System – Os is interface between Human Being and Machine. Platform is nothing but Processor + Os .
Reference :
git clone remote
to create new repository in github cloud , then create a local repo and clone 2 repositories using git clone remote (repo link).
git add filename
git add .
to add a single file using git add and add all the files which present in the current repo the use git add . | . represent add all the files.
git commit -m "message"
commit the added file using git commit and put some mesagges about the file using -m ” ” .
some ideas of commit messages are available in below mentioned link.
Reference : conventional commit.org | https://www.conventionalcommits.org/en/v1.0.0/
git rm --cached filename
if incase want to remove the added file use git remove
git rm --cached -f filename
-f --> forcefully remove the file.
git push
push the commited file from the local to cloud repo using git push. it will push the file to remote repository.
git pull
when u need to change or edit or modify the remote file first you will pull the file to local repository from remote using git pull.
git branch
Branch means where will you store the files in git remote.git branch is to specify the branch name it will push the file to current remote branch.
git checkout -b "branchname"
to create a new branch.
git checkout branchname
check the created branch or new branch
git branch -M branchname
to modify or change the branch name
git branch -a
to listout all branches.
git status
check all the status of previously used command like know the added file is staged or unstaged
Reference : https://www.markdownguide.org/cheat-sheet/
markdown cheathseet for readme file
Reference : conventional commit.org | https://www.conventionalcommits.org/en/v1.0.0/
for commit messages.
git clone remote
to create new repository in github cloud , then create a local repo and clone 2 repositories using git clone remote (repo link).
git add filename
git add .
to add a single file using git add and add all the files which present in the current repo the use git add . | . represent add all the files.
git commit -m "message"
commit the added file using git commit and put some mesagges about the file using -m ” ” .
some ideas of commit messages are available in below mentioned link.
Reference : conventional commit.org | https://www.conventionalcommits.org/en/v1.0.0/
git rm --cached filename
if incase want to remove the added file use git remove
git rm --cached -f filename
-f --> forcefully remove the file.
git push
push the commited file from the local to cloud repo using git push. it will push the file to remote repository.
git pull
when u need to change or edit or modify the remote file first you will pull the file to local repository from remote using git pull.
git branch
Branch means where will you store the files in git remote.git branch is to specify the branch name it will push the file to current remote branch.
git checkout -b "branchname"
to create a new branch.
git checkout branchname
check the created branch or new branch
git branch -M branchname
to modify or change the branch name
git branch -a
to listout all branches.
git status
check all the status of previously used command like know the added file is staged or unstaged
Reference : https://www.markdownguide.org/cheat-sheet/
markdown cheathseet for readme file
Reference : conventional commit.org | https://www.conventionalcommits.org/en/v1.0.0/
for commit messages.
Java is invented in 1991 by James Gosling of Sun Microsystems (later acquired by Oracle)
WORA –> write once run anywhere
Rules and syntax are derived from C and C++ Languages.
Java is a technology consisting of both a programming language and a software platform
To create an application using java , we need to download the JDK (java development kit) . which is available for all platforms (OS).
JDK
.java --> compiler | converter | Translator --> Bytecode
write the program in java, then a compiler turns a program into java bytecode.which converts .javafile to .classfile
compiler –> translate the entire source code in a single run and its performance is higher.
interpreter –> translate the entire source code line by line and its performance is lower.
Bytecode
Instruction set for java virtual machine (Jvm) , which means bytecode is not human readable. its is platform (os) independent.
JVM
JRE
Reference : https://www.ibm.com/topics/java
Java is invented in 1991 by James Gosling of Sun Microsystems (later acquired by Oracle)
WORA –> write once run anywhere
Rules and syntax are derived from C and C++ Languages.
Java is a technology consisting of both a programming language and a software platform
To create an application using java , we need to download the JDK (java development kit) . which is available for all platforms (OS).
JDK
.java --> compiler | converter | Translator --> Bytecode
write the program in java, then a compiler turns a program into java bytecode.which converts .javafile to .classfile
compiler –> translate the entire source code in a single run and its performance is higher.
interpreter –> translate the entire source code line by line and its performance is lower.
Bytecode
Instruction set for java virtual machine (Jvm) , which means bytecode is not human readable. its is platform (os) independent.
JVM
JRE
Reference : https://www.ibm.com/topics/java
To know the user is using id command
id username
sudo
permits the user to execute a command as a super user at the admin level
su
su --> switch user
su -username
id
exit
Zip
zip filename file
zip filename *.txt
zip -sf filename.zip
to view the zipped file.
unzip
unzip filename
to make another directory to unzip the file or rename the exisisting file.
ulimit
to manage the resources of the particular user.
ulimit -a
soft limit cannot more than hard limit
cat /etc/security/limits.conf
type> can have the two values:
type
to know where the command it will present
type command
which
where the command will locate
which mv
whatis
to know the description of the command
whereis
locate the binary, source, and manual page files for a command
apropos
search the manual page names and descriptions
change attribute
which makes the file unchangeable in the same location. but will copy the file in another location and edit the file.
sudo chattr +i filename
lsattr
sudo chattr -i file
it will convert unchangeable file to changeable file
sudo chattr -R +i dir1
sudo chattr -R -i dir1
to change the directory to unmutable
pidof ---> find the process ID of running program
vi test --> new process
ps -ef | grep vi
pidof vi
pwdx 8279
to know the present working directory of vi using pid.
NI –> (-20 to 19) highest priority to lowest priority range.
1 to 19 –> non root users will aslo set the ni values
-20 to -1 –> root user only set the value
to modify the program priority.
ps -l --> process list
to change the priority of the running program
nice -n 11 ps -l
renice
changing the priority of the running program.
useradd
create a new user or update default new user information.
tail /etc/passwd –> userslist
adduser –> adduser, addgroup – add a user or group to the system
sudo passwd sample
to set a password for sample user.
sudo passwd -Sa
to check all the users having password or not.
set a password for the sample user
after setting the passwd for sample user
sudo passwd -d sample
d --> delete
NP --> no passwd
user-delete
sudo userdel sample
sudo userdel -r sample --> to delete with home
to create group with user
to create a group
addgroup :
deletegroup :
sudo groupdel groupname
sudo delgroup groupname
sudo usermod -aG sudo username
permission to using i commands for new user
to give sudo or root previlage for new user.
To know the user is using id command
id username
sudo
permits the user to execute a command as a super user at the admin level
su
su --> switch user
su -username
id
exit
Zip
zip filename file
zip filename *.txt
zip -sf filename.zip
to view the zipped file.
unzip
unzip filename
to make another directory to unzip the file or rename the exisisting file.
ulimit
to manage the resources of the particular user.
ulimit -a
soft limit cannot more than hard limit
cat /etc/security/limits.conf
type> can have the two values:
type
to know where the command it will present
type command
which
where the command will locate
which mv
whatis
to know the description of the command
whereis
locate the binary, source, and manual page files for a command
apropos
search the manual page names and descriptions
change attribute
which makes the file unchangeable in the same location. but will copy the file in another location and edit the file.
sudo chattr +i filename
lsattr
sudo chattr -i file
it will convert unchangeable file to changeable file
sudo chattr -R +i dir1
sudo chattr -R -i dir1
to change the directory to unmutable
pidof ---> find the process ID of running program
vi test --> new process
ps -ef | grep vi
pidof vi
pwdx 8279
to know the present working directory of vi using pid.
NI –> (-20 to 19) highest priority to lowest priority range.
1 to 19 –> non root users will aslo set the ni values
-20 to -1 –> root user only set the value
to modify the program priority.
ps -l --> process list
to change the priority of the running program
nice -n 11 ps -l
renice
changing the priority of the running program.
useradd
create a new user or update default new user information.
tail /etc/passwd –> userslist
adduser –> adduser, addgroup – add a user or group to the system
sudo passwd sample
to set a password for sample user.
sudo passwd -Sa
to check all the users having password or not.
set a password for the sample user
after setting the passwd for sample user
sudo passwd -d sample
d --> delete
NP --> no passwd
user-delete
sudo userdel sample
sudo userdel -r sample --> to delete with home
to create group with user
to create a group
addgroup :
deletegroup :
sudo groupdel groupname
sudo delgroup groupname
sudo usermod -aG sudo username
permission to using i commands for new user
to give sudo or root previlage for new user.
sudo apt install mariadb-server mariadb-client
sudo systemctl status mariadb.servcie
to check the mariadb services.
sudo systemctl enable mariadb.service
sudo systemctl start mariadb.service
sudo systemctl stop mariadb.service
sudo mysql_secure_installation
enter into the database using
mysql -u root -p
to view the default databases which present in mariadb using
show databases;
create new database using
create database name;
show created database
show databases:
to use the exsisting database
use databasename;
jobs -l
t will dsiplay the job with process id
jobs -p
it will display only pid
fg % 1
foreground
ctrl + z to stop the job
bg % 2
we cannot stop it runs in background
report a snapshot for the current process
ps aux ---> it will dsiplay all users
ps x
kill -9 pid1
used to kill the process
display running process in tree structure.
sudo apt install mariadb-server mariadb-client
sudo systemctl status mariadb.servcie
to check the mariadb services.
sudo systemctl enable mariadb.service
sudo systemctl start mariadb.service
sudo systemctl stop mariadb.service
sudo mysql_secure_installation
enter into the database using
mysql -u root -p
to view the default databases which present in mariadb using
show databases;
create new database using
create database name;
show created database
show databases:
to use the exsisting database
use databasename;
jobs -l
t will dsiplay the job with process id
jobs -p
it will display only pid
fg % 1
foreground
ctrl + z to stop the job
bg % 2
we cannot stop it runs in background
report a snapshot for the current process
ps aux ---> it will dsiplay all users
ps x
kill -9 pid1
used to kill the process
display running process in tree structure.
apache -> Hypertext transfer protocol webserver.
sudo apt install apache2 -y
install apache2 webserver in ubuntu.
sudo systemctl status apache2
apache2 status check
sudo systemctl enable apache2
persistently run across the reboot
cd /var/www/html
ubuntu default apache webpage.
sudo vim /etc/hosts
customize the localhost name 127.0.0.1 localhost to eladhruv.in. it will reflect only in local server.
rm index.html --> it removes default webpage
we customize the default page.
join file1 file2
join lines of two files on a common field. if no common fields are there then error should be occurs.
join -1 2 -2 1 s3.txt s4.txt
print unpairable lines using column number where FILE NUM is 1 or 2, corresponding to FILE1 or FILE2.
to determine the file type.
file filename
file -b filename
b --> brief
file *
it display all the file type including directory.
It will create a empty file the it will change the time snap.
touch filename
touch file{1..20}.txt
It will create 20 empty files. file size are user defined we can create more files.
touch -d tomorrow filename
It will change the day
touch -r s1.txt s2.txt
r --> reference
time reference from s1.txt
It display calendar
Reverse the character
> output Redirection | < input redirection
cat > filename
it will create a new file and we can give input to the file
cat < filename
it will display the file content
wc < text.txt > text1.txt
cat < text1
it will save the wc of the file to file1
cat >> filename
adding the content to exisiting file
>> append
tee – read from standard input and write to standard output and files
df -Th | tee df.txt
grep – print lines that match patterns
grep "word" filename
grep "word" file1 file2
grep -i "word" file1 file2
apache -> Hypertext transfer protocol webserver.
sudo apt install apache2 -y
install apache2 webserver in ubuntu.
sudo systemctl status apache2
apache2 status check
sudo systemctl enable apache2
persistently run across the reboot
cd /var/www/html
ubuntu default apache webpage.
sudo vim /etc/hosts
customize the localhost name 127.0.0.1 localhost to eladhruv.in. it will reflect only in local server.
rm index.html --> it removes default webpage
we customize the default page.
join file1 file2
join lines of two files on a common field. if no common fields are there then error should be occurs.
join -1 2 -2 1 s3.txt s4.txt
print unpairable lines using column number where FILE NUM is 1 or 2, corresponding to FILE1 or FILE2.
to determine the file type.
file filename
file -b filename
b --> brief
file *
it display all the file type including directory.
It will create a empty file the it will change the time snap.
touch filename
touch file{1..20}.txt
It will create 20 empty files. file size are user defined we can create more files.
touch -d tomorrow filename
It will change the day
touch -r s1.txt s2.txt
r --> reference
time reference from s1.txt
It display calendar
Reverse the character
> output Redirection | < input redirection
cat > filename
it will create a new file and we can give input to the file
cat < filename
it will display the file content
wc < text.txt > text1.txt
cat < text1
it will save the wc of the file to file1
cat >> filename
adding the content to exisiting file
>> append
tee – read from standard input and write to standard output and files
df -Th | tee df.txt
grep – print lines that match patterns
grep "word" filename
grep "word" file1 file2
grep -i "word" file1 file2
