Month: February 2019
C++ sizeof Operator
sizeof is a keyword and a compile-time operator that determines the size of given variable OR data-type, and returns result in bytes.
We can also use sizeof keyword to get size of classes, structures, unions and any other user defined data type.
Syntex:
sizeof ( data type)
to get the size of given datatype. like: sizeof(int)
or
sizeof (variable name)
Example program:
#include <iostream>
using namespace std;
int main() {
cout << "Size of char : " << sizeof(char) << endl;
cout << "Size of int : " << sizeof(int) << endl;
cout << "Size of short int : " << sizeof(short int) << endl;
cout << "Size of long int : " << sizeof(long int) << endl;
cout << "Size of float : " << sizeof(float) << endl;
cout << "Size of double : " << sizeof(double) << endl;
cout << "Size of wchar_t : " << sizeof(wchar_t) << endl;
return 0;
}
Blockchain from Bitcoin’s perspective
Blockchain technology is used as basis for a secure and transparent distributed ledger for the Bitcoin cryptocurrency. Its decentralized, public and immutable properties solve the double spending problem and allow every participant of the network to read the transaction history, help in
the validation process and pay and receive Bitcoin.
Cryptographically complex math ensures that everyone can do transactions with everyone without the need for a trusted third party. Next to financial transactions, this also holds for other claims. Entities can put claims on a decentralized ledger by digitally signing it, which allows any other entity to verify that these claims are made by that specific entity.
What is CURL ?
cURL is basically a Client URL Library or a Command line tool, can be considered as a non-interactive web browser which is used to move data to or from server which supports various protocols such as:
(DICT, FILE, FTP, FTPS, GOPHER, HTTP, HTTPS, IMAP, IMAPS, LDAP, LDAPS, POP3, POP3S, RTMP, RTSP, SCP, SFTP, SMB, SMBS, SMTP, SMTPS, TELNET and TFTP)
cURL allows users to perform multiple files download / uploads with a single command. Multiple URLs can be specified in single command and they will be fetched in given order. It also supports proxy details, file uploads via FTP, sending requests over HTTP protocol, establishing connections via SSL, getting and setting cookies, user and password authentication, SMTP authentication and sending emails, authentication via POP3 and IMAP and many more. Simply, cURL can be used for everything that is related to data transfer using Internet protocols.
Install Hyperledger Fabric on Ubuntu 18.04.1 – Step by Step
Installation of Hyperledger Fabric on Ubuntu is very straight forward and is a step-by-step process. We can majorly divide this whole process into two major parts: First we need to install all pre-requisites and then we proceed towards installation of Fabric itself.
Installing Prerequisites for Hyperledger Fabric:
- CURL
- GO Programming Language with setup of path variable
- Docker & Docker Compose
- Node.js Runtime & NPM
- PYTHON
sudo apt-get install curlsudo apt-get install golang-goexport GOPATH=$HOME/goexport PATH=$PATH:$GOPATH/binsudo apt-get install nodejssudo apt-get install npmsudo apt-get install pythonsudo apt-get install dockercurl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"sudo apt-get updateapt-cache policy docker-cesudo apt-get install -y docker-cesudo apt-get install docker-composesudo apt-get upgradeTill now the environment is ready to install Hyperledger Fabric, Now we will download fabric samples. To do that run following commands in terminal one by one…
sudo curl -sSL https://goo.gl/6wtTN5 | sudo bash -s 1.1.0sudo chmod 777 -R fabric-samples
Now go into first-network directory which is inside fabric-samples folder and then we will run generate script that will create certificates and keys for the entities on our first blockchain network. This will also create genesis block (first block on blockchain)
cd fabric-samples/first-network
sudo ./byfn.sh generate
Bring your first network up by running following command. byfn stands for “Build Your First Network”
sudo ./byfn.sh up If everything works fine you should see start screen of fabric network. To bring network down following command is used.
sudo ./byfn.sh down