tech.notes

7.21.2017

Mac Cheat Sheet

1. Install sshpass
$ brew install http://git.io/sshpass.rb

2. Using iTerm2, configure profiles and use sshpass so there's no need to enter passwords for ssh, follow this post for configuring iTerm2. What worked for me is in Command, select "Login shell", then send text at start:
sshpass -p 'password' ssh -o StrictHostKeyChecking=no user@server

7.20.2017

Postgres Cheat Sheet

1. Postgres version
$ psql --version

2. Connect to server locally using default postgres acct
$ psql -U postgres

3. Connect with a password
$ psql -U postgres -W

4. Common commands
\h - help
\q - quit
\l - list databases
\d - list tables
\d table - describe table

5. Create db
postgres=# CREATE DATABASE testdb;

6. Use the db
postgres=# \c testdb;
testdb=#

7. List of users
postgres=# \du

8. List postgres versions running
$ pg_lsclusters
Ver Cluster Port Status Owner    Data directory               Log file
9.1 main    5433 down   postgres /var/lib/postgresql/9.1/main /var/log/postgresql/postgresql-9.1-main.log
9.4 main    5432 down   postgres /var/lib/postgresql/9.4/main /var/log/postgresql/postgresql-9.4-main.log
9.6 main    5434 online postgres /var/lib/postgresql/9.6/main /var/log/postgresql/postgresql-9.6-main.log

9. Start/Stop/Restart/Status of postgresql
$ sudo systemctl start postgresql
$ sudo systemctl stop postgresql
$ sudo systemctl restart postgresql
$ sudo systemctl status postgresql

10. Backup/Restore
$ pg_dump -Fc -h hostname -p 5432 -d dbname -f /path/backupfilename
$ pg_restore -d dbname -v -1 /path/backupfilename

11. Cron daily backup
$ crontab -e
0 5 * * * export PGPASSWORD=MyPass && pg_dump -Fc -h hostname -p 5432 -d dbname -f /path/backupfilename_`date +20\%y\%m\%d` >> /path/pg_dump_dbname.log 2>&1

Install Postgres on Mac

Followed this post

1. Go to http://postgresapp.com/ then download and install
2. Add Postgres to PATH
$ vi ~/.bash_profile
export PATH=$PATH:/Applications/Postgres.app/Contents/Versions/latest/bin
$ source ~/.bash_profile
3. Start Postgres by double clicking the app, then on the top icon, start "Initialize"
4. Try connecting using default postgres role
$ psql -U postgres
psql (9.6.3)
Type "help" for help.

postgres=#

Install Python 3.6 on MacOS


Generally followed this post

I. Install brew
1. Install Xcode from the App Store
2. Install Xcode’s separate Command Line Tools app
$ xcode-select --install
3. Install and setup homebrew
$ /usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
4. Make sure brew is in PATH
$ vi ~/.bash_profile
export PATH=/usr/local/bin:$PATH
5. Source it
$ source ~/.bash_profile
6. Try brew
$ brew doctor
Your system is ready to brew.

II. Install Python
$ brew search python
$ brew install python3
$ python3 --version
Python 3.6.2
To install a python package
$ pip3 install package_name
To upgrade python
$ brew update
$ brew upgrade python3

III. Creating Virtual environments
$ mkdir sample_project
$ cd sample_project
$ python3.6 -m venv my_env
$ source my_env/bin/activate

Change bash command prompt in Debian

Followed this post

$ vi /etc/bash.bashrc
Add this at the end:

# If id command returns zero, you have root access.
if [ $(id -u) -eq 0 ];
then # you are root, set red colour prompt
   PS1="\\[$(tput setaf 1)\\][\\u@\\h:\\w] (apps)# \\[$(tput sgr0)\\]"
else # normal
   PS1="[\\u@\\h:\\w] (apps)$ "
fi

2.12.2017

Angular Cheat Sheet


Creating Components

import { Component } from '@angular/core'
@Component({
 selector: 'courses',
 template: '<h2>Courses</h2>'
})
export class Component { }

Then, register them in AppModule (or the module the belong to):

@NgModule({
 declarations: [CoursesComponent]
})
export class AppModule { … }

Using Components

import { CoursesComponent } from './courses.component'
@Component({
 template: '<courses></courses>'
})

Templates
Interpolation syntax:
{{ title }}

Displaying lists:
<ul>
 <li *ngFor=“let course of courses”>
 {{ course }}
 </li>
</ul>

Services

import { Injectable } from '@angular/core';
@Injectable()
export class CourseService {
}

Dependency Injection

Register a service as a provider in AppModule (or the module it belongs to):

@NgModule({
 providers: [CourseService]
})
export class AppModule { … }

Then, inject it into the constructor of the components that need it:

export class CourseComponent {
 constructor(courseService: CourseService) {}
}

Directives
Basic structure
import { Directive } from '@angular/core'

@Directive({
 selector: '[autoGrow]',
 host: {
 '(focus)': 'onFocus()',
 '(blur)': 'onBlur()'
 }
})
export class AutoGrowDirective {
 onFocus() { … }
 onBlur() { … }
}

To access and modify DOM elements

import { ElementRef, Renderer } from '@angular/core'

export class AutoGrowDirective {
 constructor(
 private el: ElementRef,
 private renderer: Renderer) {
 }
 onFocus(){
 this.renderer.setElementStyle(this.el.nativeElement,
 'width', '200');
 }
}

Registration

Once you implement a directive, you should register it in AppModule (or the module it belong to):

@NgModule({
 declarations: [AutoGrowDirective]
})
export class AppModule { }

Angular Bindings

Interpolation
<h1>{{ title }}</h1>

Property binding
<img [src]="imageUrl" />
<img bind-src="imageUrl" />

Class binding
<li [class.active]="isActive" />

Style binding
<button [style.backgroundColor]="isActive ? 'blue' : 'gray'">

Event binding
<button (click)="onClick($event)">
<button on-click="onClick($event)">

Two-way binding
<input type="text" [(ngModel)]="firstName">
<input type="text" bindon-ngModel="firstName">

Input Properties
Using @Input annotation
import { Input } from ‘@angular/core’;
@Component(…)
export class FavoriteComponent {
 @Input(‘is-favorite’) isFavorite = false;
}

Using component metadata
@Component({
 inputs: [‘isFavorite:is-favorite’]
})
export class FavoriteComponent {
 isFavorite = false;
}

In the host component
<favorite [is-favorite]=“post.isFavorite”></favorite>


Output Properties
Using @Output annotation
import { Output } from ‘@angular/core’;
@Component(…)
export class FavoriteComponent {
 @Output(‘favorite-change’) change = new EventEmitter();

 onClick() {
 this.change.emit({ newValue: this.isFavorite });
 }
}


Using component metadata
@Component({
 outputs: [‘change:favoriteChange’]
})
export class FavoriteComponent {
 change = new EventEmitter();

 onClick() {
 this.change.emit({ newValue: this.isFavorite });
 }
}


In the host component
<favorite (favoriteChange)=“onChange()”></favorite>


Templates
@Component({
 template: ‘…’, // or
 templateUrl: ‘app/template.template.html’
})


Styles
@Component({
 styles: [‘…’],
 styleUrls: [‘…’, ‘…’];
})

Getting Ready for Angular Development


On Ubuntu:
Install nodejs
1. $ sudo apt-get install nodejs
2. $ sudo ln -s /usr/bin/nodejs /usr/bin/node
3. $ sudo apt-get install npm

Install typescript
1. $ sudo npm install -g typescript
2. $ sudo npm install -g typings

Install angular cli
1. $ sudo npm install -g @angular/cli

On Debian:
$ curl -sL https://raw.githubusercontent.com/creationix/nvm/v0.32.0/install.sh -o install_nvm.sh
$ bash install_nvm.sh
$ source ~/.profile
$ nvm ls-remote
$ nvm install 8.5.0
$ nvm use 8.5.0
$ node -v
v8.5.0
$ npm -v
5.3.0
$ npm install -g yarn
$ yarn global add @angular/cli
$ vi ~/.profile
# yarn
export PATH="$PATH:`yarn global bin`"
$ ng set --global packageManager=yarn
$ ng --version
@angular/cli: 1.4.3
node: 8.5.0
os: linux x64

On Mac:
I followed this and this

Install nodejs
1. Install xcode
$ xcode-select --install
2. Install nvm
$ curl -o- https://raw.githubusercontent.com/creationix/nvm/v0.33.2/install.sh | bash
3. Open another bash session to get settings from nvm install
4. List installed node versions
$ nvm list
5. Or list from the cloud (last 9 versions)
$ nvm ls-remote | tail -n9
6. Install latest
$ nvm install 8.2.1
7. Setup this version as default
$ nvm use 8.2.1
$ nvm alias default 8.2.1
8. Check node version
$ node -v
v8.2.1
9. Update npm
$ npm install -g npm
10. Check npm version
$ npm -v
5.3.0

Install yarn package manager
1. $ npm install -g yarn

Install angular cli
1. $ yarn global add @angular/cli@1.2.7
2. Check version
$ ng --version
@angular/cli: 1.2.7
node: 8.2.1
os: darwin x64
3. Globally config angular-cli to use yarn
$ ng set --global packageManager=yarn

Test scaffold first angular app
1. $ ng new hello-world-app
2. Start server
$ cd hello-world-app
$ ng serve
3. Browse http://localhost:4200

Setup IDE
1. Install Visual Studio Code