----------------------------------------
cheat sheet
----------------------------------------
https://spacetrack.github.io/cheat-sheet.txt
----------------------------------------
2020-06-03, 19:15
----------------------------------------


go_000_0000 table of contents

go_100_0000 ...
go_200_0000 ...
go_300_0000 ...

go_400_0000 ...
go_401_0050 Random
go_401_0060 curl examples

go_402_0000 crypto
go_402_0100 openssl
go_402_0110 encryption with openssl
go_402_0120 run a web-server with openssl
go_402_0200 hashing
go_402_0210 proof to be first author

go_403_0000 bash
go_403_0010 bash: redirect stdin stdout stderr
go_403_0020 bash: for loops
go_403_0030 bash: multidimensional arrays

go_404_0000 windows powershell
go_404_0001 windows powershell: get version
go_404_0002 windows powershell: force to use UTF-8, ascii, ...
go_404_0010 windows powershell: run command elevated
go_404_0020 windows powershell: send e-mail
go_404_0030 windows powershell: taskschd windows cron
go_404_0035 windows powershell: find file
go_404_0040 windows powershell: find string in files (grep -r)
go_404_0041 windows powershell: get number of lines (wc -l)
go_404_0045 windows powershell: URL encode / decode
go_404_0046 windows powershell: BASE64 encode / decode
go_404_0050 windows powershell: GUID

go_410_0000 linux admin
go_410_0010 linux version
go_410_0015 linux reboot needed
go_410_0100 linux ubuntu resize partition

go_411_0000 windows admin
go_411_0100 windows admin: listening to port

go_420_0001 tmux

go_421_0000 ssh
go_421_0001 ssh: run an HTTP server on remote node and browse through local web

go_500_0000 ...
go_501_0010 FFMPEG
go_501_0020 mstsc

go_502_0000 haproxy
go_502_0010 haproxy: validate config

go_503_0000 what is my ip address
go_503_0020 what is my ip address: get external ip address

go_590_0000 Azure
go_590_0001 download attachments of Azure DevOps work item

go_600_0000 development
go_601_0000 git
go_601_0010 git log: simple and well formatted
go_601_0015 git tag: list tags in MAJOR-MINOR-PATCH-order
go_601_0020 git merge: dry run

go_602_0000 go(lang)
go_602_0010 go(lang) in docker
go_602_1000 go(lang) programming

go_603_0000 c#
go_603_0100 c# dotnet commands
go_603_1000 c# dotnet programming
go_603_1010 c# dotnet programming: Refresh ASP.NET Core MVC view without reloading the application

go_604_0000 java
go_604_0100 java commmands
go_604_0200 java Lego Mindstorm
go_604_1000 java programming

go_605_0000 javascript
go_605_1000 javascript programming


go_700_0000 ...
go_701_0000 mysql
go_701_0001 mysql: manage users
go_701_0002 mysql: change the default collation
go_701_0003 mysql: store encrypted login on file system
go_701_0004 mysql: dump database

go_800_0000 ...
go_800_0010 raspberry pi raspi

go_900_0000 misc

---:---:---
---:---:---
---:---:---
go_400_0000 ...





---:---:---
go_401_0050 Random
##random

# get 12 random chars
$ cat /dev/urandom | tr -cd 'a-zA-Z0-9.-' | head -c12

# get 12 random bytes
$ cat /dev/urandom | head -c12 | base64



---:---:---
go_401_0060 curl examples

# curl silent but with errors
$ curl --insecure --silent --fail --show-error https://spacetrack.github.io/invalid/file.txt

# curl with HTTP response code on output
$ curl --insecure --silent --write-out "%{stderr}HTTP/%{http_version} %{response_code}" https://spacetrack.github.io/invalid/file.txt




---:---:---
go_402_0000 crypto
go_402_0100 openssl
go_402_0110 encryption with openssl
##openssl ##encrypt ##decrypt

# encrypt files
$ set +o history
$ tar -cvf - * | bzip2 -9 | openssl enc -aes-256-cbc -md sha512 -pbkdf2 -iter 100000 -salt -in - -out - -e -k "my-secret-passwd" | base64 > files.tar.bz2.enc.b64.txt
$ set -o history

# decrypt files
$ set +o history
$ cat files.tar.bz2.enc.b64.txt | base64 -d | openssl enc -aes-256-cbc -md sha512 -pbkdf2 -iter 100000 -salt -in - -out - -d -k "my-secret-passwd" | bzip2 -d | tar -xvf -
$ set -o history

# openssl shortcut
$ cat > opensslpipe.sh << EOF
#!/bin/bash
openssl enc -aes-256-cbc -md sha512 -pbkdf2 -iter 100000 -salt -in - -out - \${1} -k \${2}
EOF

# encrypt/decrypt files
$ set +o history
$ tar -cvf - * | bzip2 -9 | opensslpipe.sh -e "my-secret-passwd" | base64 > files.tar.bz2.enc.b64.txt
$ cat files.tar.bz2.enc.b64.txt | base64 -d | opensslpipe.sh -d "my-secret-passwd" | bzip2 -d | tar -xvf - 
$ set -o history

# encrypt/decrypt (short) text
$ set +o history
$ echo 'a secret message' | opensslpipe.sh -e 'my-secret-passwd' | base64
$ echo 'U2FsdGVkX1+OdddqCYCobh5tJL0hvX7eO/c0wi10yNfbbs73jgzNfdLj/MFVgl2z' | base64 -d | opensslpipe.sh -d 'my-secret-passwd'
$ set -o history



---:---:---
go_402_0120 run a web-server with openssl
##openssl ##tinywebserver

# credits
$ start https://www.devdungeon.com/content/one-line-http-servers

# create a self-signed certificate (or get one from Let's Encrypt)
$ openssl req -newkey rsa:2048 -nodes -keyout private-key.pem -x509 -days 365 -out certificate.pem

# start the web server
$ openssl s_server -key private-key.pem -cert certificate.pem -accept 8080 -WWW



---:---:---
go_402_0200 hashing
go_402_0210 proof to be first author
##sha256

# store the text in static file
$ vi hello-world.txt

# hash the file
$ sha256sum hello-world.txt

53ebf7070d1dd57254a317f4e3ca898f3a2ebc1c017ace73e707e096a29bdc51 *hello-world.txt

# publish the resulting hash, e. g. on twitter or a blockchain ...
curl -X POST 'https://api.twitter.com/1.1/statuses/update.json?status=hello' 
  --header 'authorization: OAuth
  oauth_consumer_key="oauth_customer_key",
  oauth_nonce="generated_oauth_nonce",
  oauth_signature="generated_oauth_signature",
  oauth_signature_method="HMAC-SHA1",
  oauth_timestamp="generated_timestamp",
  oauth_token="oauth_token",
  oauth_version="1.0"'



---:---:---
go_403_0000 bash
go_403_0010 bash: redirect stdin stdout stderr

# credits
$ start http://www.tldp.org/LDP/abs/html/io-redirection.html

----------------------------------------

1>filename
  # Redirect stdout to file "filename."
  
1>>filename
  # Redirect and append stdout to file "filename."
  
2>filename
  # Redirect stderr to file "filename."
  
2>>filename
  # Redirect and append stderr to file "filename."
  
&>filename
  # Redirect both stdout and stderr to file "filename."
  # This operator is now functional, as of Bash 4, final release.

2>&1
  # Redirects stderr to stdout.
  # Error messages get sent to same place as standard output.
  
  >>filename 2>&1
  
  # If redirecting both stdout and stderr,
  # the order of the commands makes a difference.
  
----------------------------------------

# redirect stdout to file1, stderr to file2, stdout + stderr to file3
$ { { echo "1 hello world"; (>&2 echo "2 hello error"); echo "3 hello world"; (>&2 echo "4 hello error"); } 1> >(tee stdout.log) 2> >(tee stderr.log >&2); } >> all.log 2>&1

# redirect stdout to mail 1, stderr to mail 2
$ { { echo "1 hello world"; (>&2 echo "2 hello error"); echo "3 hello world"; (>&2 echo "4 hello error"); } | mail -s "test stdout `date`" bwinkler@netmediaeurope.com; } 2>&1 | mail -s "test stderr `date`" bwinkler@netmediaeurope.com

# redirect stdout to nothing, stderr to mail, stdout + stderr to file
$ { { echo "1 hello world"; (>&2 echo "2 hello error"); echo "3 hello world"; (>&2 echo "4 hello error"); } 1> >(tee stdout.log) 2> >(tee /dev/stderr | mail -s "test stderr `date`" bwinkler@netmediaeurope.com); } >> all.log 2>&1



---:---:---
go_403_0030 bash: multidimensional arrays

# blog: how to simulate multidimensional arrays
$ start https://spacetrack.github.io/blog/2016/bash-mehrdimensionale-arrays.html



---:---:---
go_404_0000 windows powershell
go_404_0001 windows powershell: get version

# get version of PowerShell
> $PSVersionTable.PSVersion

---:---:---
go_404_0002 windows powershell: force to use UTF-8, ascii, ...

# set char encoding in PowerShell version 5.1 or higher
> $PSDefaultParameterValues['Out-File:Encoding'] = 'utf8'
> $PSDefaultParameterValues['Out-File:Encoding'] = 'ascii'

---:---:---
go_404_0010 windows powershell: run command elevated

# run command elevated (= as administrator), e. g. cmd
> powershell -Command "Start-Process -Verb runAs cmd.exe"

# run command elevated (= as administrator), e. g. create a Windows service
> powershell -Command "Start-Process -Verb runAs sc.exe -ArgumentList 'create', 'MyService', 'BinPath=C:\temp\MyService.exe'"
> & sc.exe query MyService


---:---:---
go_403_0020 bash: for loops

$ for i in {0..9}; do echo $i; done
$ for ((i=0;i<10;i++)){ echo $i;}
$ for var in list; do command; done



---:---:---
go_404_0020 windows powershell: send e-mail

# credits
> start https://blog.mailtrap.io/powershell-send-email/

# send e-mail 
> Send-MailMessage `
-UseSsl `
-Credential (Get-Credential) `
-SmtpServer 'mail.gmx.net' `
-Port 587 `
-To 'bjoern.winkler+test-powershell@gmail.com' `
-From 'bjoern_winkler@gmx.de' `
-Subject 'test from powershell' `
-Body 'test from powershell'



---:---:---
go_404_0030 windows powershell: taskschd windows cron

# credits
> start https://blog.netwrix.com/2018/07/03/how-to-automate-powershell-scripts-with-task-scheduler/

# create new task from powershell
> $Trigger = New-ScheduledTaskTrigger -At 4:00am –Daily
> $User = "NT AUTHORITY\SYSTEM"
> $Action = New-ScheduledTaskAction -Execute "PowerShell.exe" -Argument "C:\my-scripts\my-script.ps1"
> Register-ScheduledTask -TaskName "MonitorGroupMembership" -Trigger $Trigger -User $User -Action $Action -RunLevel Highest –Force

# create new task from powershell: one line! ;-)
> Register-ScheduledTask -TaskName "Dump MySQL database" -Trigger $(New-ScheduledTaskTrigger -At 4:00am –Daily) -User "NT AUTHORITY\SYSTEM" -Action $(New-ScheduledTaskAction -Execute "PowerShell.exe" -Argument "C:\scripts\mysql-dump.ps1") -RunLevel Highest –Force

# check if the daily task has been configured
> Get-ScheduledTask | Select-String Dump

# check if "NextRunTime" shows tomorrow, 4:00 am
> Get-ScheduledTaskInfo -TaskName "Dump MySQL database"

---:---:---
go_404_0035 windows powershell: find file

# find a file in a directory recursively
> dir -recurse | Where-Object { $_.PSIsContainer } | Select FullName | convertto-csv

---:---:---
go_404_0040 windows powershell: find string in files (grep -r)

# credits
> start https://stackoverflow.com/a/8153857

# search a string in multiple files and return the names of files
> Get-ChildItem -Recurse | Select-String "unsub" -List | Select Path

---:---:---
go_404_0041 windows powershell: get number of lines (wc -l)

# get number of PDF files in a directory
$ ls -la *.pdf | wc -l
> dir *.pdf | Measure-Object -line



---:---:---
go_404_0045 windows powershell: URL encode / decode
##urlencode ##urldecode

# powershell 5 URL encode/decode:
> [uri]::EscapeDataString("hallo welt")
> [uri]::UnescapeDataString("hallo%20welt")

# powershell 6 URL encode/decode
> [System.Web.HttpUtility]::UrlEncode("hallo welt")
> [System.Web.HttpUtility]::UrlDecode("hallo+welt")

---:---:---
go_404_0046 windows powershell: BASE64 encode / decode

# base64 encode
> [Convert]::ToBase64String([System.Text.Encoding]::UTF8.GetBytes("hello world"))

# base64 decode 
> [System.Text.Encoding]::UTF8.GetString([Convert]::FromBase64String("aGVsbG8gd29ybGQ="))

---:---:---
go_404_0050 windows powershell: GUID

# create a new GUID
> New-Guid

# get string of new GUID
> (New-Guid).Guid

# send new GUID to clipboard
> New-Guid | Set-Clipboard

---:---:---
go_410_0000 linux admin

---:---:---
go_410_0010 linux version

# get version of ...
$ :    linux version :; cat /proc/version
$ :   ubuntu version :; lsb_release -a
$ :   centos version :; cat /etc/redhat-release
$ : raspbian version :; cat /etc/os-release

---:---:---
go_410_0015 linux reboot needed

# check if reboot is needed ...
$ : ubuntu reboot needed :; test -e /var/run/reboot-required && echo 'yes, reboot required!' || echo 'no reboot needed'
$ : centos reboot needed :; needs-restarting -r -s

---:---:---
go_410_0100 linux ubuntu resize partition

# check all available or the specified block devices
$ sudo lsblk

# check free space
$ sudo vgdisplay

# increase size of partition
$ lvresize -l +100%FREE /dev/ubuntu-vg/ubuntu-lv

# increase size of file system
$ resize2fs /dev/ubuntu-vg/ubuntu-lv

# reboot
$ sudo reboot


---:---:---
go_411_0000 windows admin
go_411_0100 windows admin: listening to port

# find exe that is listening to a port 5000 on Windows
> netstat -abon | findstr 5000
> tasklist | findstr

---:---:---
go_420_0001 tmux
##tmux ##screen

# tmux simple start
$start https://www.sitepoint.com/tmux-a-simple-start/
$start https://gist.github.com/henrik/1967800

# new window:     CTRL+b c
# list windows:   CTRL+b w
# goto window:    CTRL+b <NR>
# detach session: CTRL+b d

# split window (create panes) horizontal: CTRL+b %
# split window (create panes) vertical:   CTRL+b "
# split window - swap panes:              CRTL+b o

# tmux list detached sessions
$ tmux ls

# tmux attache session
$ tmux a #


---:---:---
go_421_0000 ssh
go_421_0001 ssh: run an HTTP server on remote node and browse through local web

# step 1: start a remote web server
remote $ python3 -m http.server 25000

# step 2: start a local ssh session
local $ ssh -L 8000:localhost:25000 id@remote -N

# step3: start a local browser 
local $ start http://localhost:8000

---:---:---
go_500_0000 ...


---:---:---
go_501_0010 FFMPEG
##ffmpeg

# ffmpeg 12seconds
$ ffmpeg -i MOV00199.avi -ss 00:00:09 flughafen.mpg

$ ffmpeg -i 2008-trailer.avi -croptop 18 -cropbottom 18 -b 30000000 -ab 128 2008-trailer_540.mpg
$ ffmpeg -i 2008-trailer_540.mpg -s 320x240 -b 400000 -ab 128 2008-trailer_320.mpg

$ ffmpeg -i "H:20 Der dicke K?.avi" -acodec libmp3lame -ab 128k -ar 44100 -vcodec mpeg4 -b 512k -s 224x176 wickie-20-der-dicke-koenig.avi

$ ffmpeg -i das_Schlossgespenst.mkv -s 320x240 -vb 400000 -ab 128000 c:das_Schlossgespenst.mpg
$ ffmpeg -i 55_Wer_anderen_eine_Grube_graebt.avi -s 320x240 -vb 400000 -ab 128000 55_Wer_anderen_eine_Grube_graebt.mpg

$ ffmpeg -i save-tv.avi -ss 00:06:52 -croptop 18 -cropbottom 18 -s 640x480 -vb 1000000 -ab 128000 ppc.mov
$ ffmpeg -i vc2010_4970_Im_Blickfeld.avi -croptop 86 -cropbottom 86 -vb 1300000 -ab 128000 -ar 44100 vc2010_4970_Im_Blickfeld.mpeg
$ ffmpeg -i vc2010_5011_Was_bringt_die_Zukunft.avi -vb 1300000 -ab 128000 -ar 44100 vc2010_5011_Was_bringt_die_Zukunft.mpeg
$ ffmpeg -i vc2010_2917_vision2010-unbekannte-heimat.flv -vb 1300000 -ab 128000 -ar 44100 vc2010_2917_vision2010-unbekannte-heimat.mpeg

$ ffmpeg -i vc2010_4878_Vision_2010_endv.wmv -s 580x326 -vb 1300000 -ab 128000 -ar 44100 vc2010_4878_Vision_2010_endv.mov

$ ffmpeg -i TV-20090512-0448-1501.hi.flv -sameq -ss 00:03:12 -t 23 hubble-1.mpeg
$ ffmpeg -i TV-20090519-1418-2201.hi.flv -sameq -ss 00:08:42 -t 24 hubble-2.mpeg
$ cat hubble-1.mpeg hubble-2.mpeg > hubble-1-2.mpeg
$ ffmpeg -i hubble-1-2.mpeg -sameq hubble.mpeg

$ ffmpeg -i "06 No Tears Anymore.m4a" -ab 192000 "06 No Tears Anymore.mp3"
$ ffmpeg -i "01 Speed of Sound.m4a" -ab 192000 "01 Speed of Sound.mp3"
$ ffmpeg -i "16 21 Guns.m4a" -ab 192000 "16 21 Guns.mp3"
$ ffmpeg -i "01 If a Song Could Get Me You.m4a" -ab 192000 "01 If a Song Could Get Me You.mp3"
$ ffmpeg -i "08 Trouble Is a Friend.m4a" -ab 192000 "08 Trouble Is a Friend.mp3"
$ ffmpeg -i "02 Locker macha (Explicit Lyrics).m4a" -ab 192000 "02 Locker macha (Explicit Lyrics).mp3"
$ ffmpeg -i "02 Sweet About Me.m4a" -ab 192000 "02 Sweet About Me.mp3"
$ ffmpeg -i "12 Mary's Boy Child.m4a" -ab 192000 "12 Mary's Boy Child.mp3"

$ ffmpeg -i "E:\data-bjw\Music\iTunes\iTunes Music\Podcasts\Adam Curry's Daily Source Code\822 DSC-822-2010-03-19.mp3" -ab 192000 -ss 00:56:30 -t 480 dsc-822-beth-thornley.mp3

# 00:33:16 - 00:04:46 = 1710sec
$ ffmpeg -i We_Love_in_Concert_a_ha_Foot_of_the_Mountain_2009-06-19_01-35_180137.avi -ss 00:04:46 -t 1710 -ab 128000 -vb 1200000 aha-1.m4v
$ ffmpeg -i a_ha_Documentary_Foot_of_the_Mountain_2009-06-28_01-10_180137.avi -ss 00:05:30 -t 5130 -ab 128000 -vb 1200000 aha-2.m4v

---:---:---
go_501_0020 mstsc
##mstsc

# credits
$ start 'https://shortcutworld.com/Windows-Remote-Desktop/win/Windows-Remote-Desktop_Shortcuts'

# start RDP session and connect to server
> mstsc /v:<server[:port]>

# start RDP session in admin mode
> mstsc /admin

# useful shortcuts in a RDP session
-    Alt+Page Up | equals standard desktop Alt+Tab
-  Alt+Page Down | equals standard desktop Alt+Shift+Tab
- Ctrl+Alt+Pause | toggle client between full-screen and window mode
-  Ctrl+Alt+Home | show connection bar when in full-screen mode
-  Ctrl+Alt+End  | equals standard desktop Ctrl+Alt+Del


---:---:---
go_502_0000 haproxy
go_502_0010 haproxy: validate config

# validate haproxy configuration
$ sudo haproxy -c -V -f /etc/haproxy/haproxy.cfg

---:---:---
go_503_0000 what is my ip address

go_503_0020 what is my ip address: get external ip address

# https://www.ipify.org/
$ curl -s 'https://api.ipify.org?format=json'

go_590_0000 Azure
go_590_0000 download attachments of Azure DevOps work item


---:---:---
go_590_0000 Azure

---:---:---
go_590_0001 download attachments of an Azure DevOps work item

# install Azure DevOps extension
> az extension add --name azure-devops

# init Azure DevOps login, you need a Personal Access Token for that
> az devops login

# find the work item
> az boards query --wiql "SELECT System.ID, System.Title, System.WorkItemType, System.AreaPath, System.AssignedTo, System.State from workitems order by System.ID asc" --organization https://dev.azure.com/YOUR-ORGANIZATION

# download the attachments (PowerShell)
> (az boards work-item show --id YOUR-WORK-ITEM-ID --organization https://dev.azure.com/YOUR-ORGANIZATION | ConvertFrom-Json).relations | Where-Object { $_.rel -eq "AttachedFile" } | ForEach-Object { Invoke-WebRequest $_.url -OutFile $_.attributes.name }

---:---:---
---:---:---
---:---:---
go_600_0000 ...
---:---:---

go_601_0000 git
go_601_0010 git log: simple and well formatted

# simple and well formatted git log output
$ git log --pretty=format:'%C(yellow)%h %C(green)%as %C(reset)%s%C(red)%d'

---:---:---
go_601_0015 git tag: list tags in MAJOR-MINOR-PATCH-order

# show git version tags in "correct" order as suggested by Semantic Versioning 2.0.0 (https://semver.org)
$ git tag -l --format='%(tag) %(subject)' | tr - \\~ | sort -V | tr \\~ -

---:---:---
go_601_0020 git merge: dry run

# test if master has been merged into current branch
$ git merge --no-commit --no-ff master
$ git diff --cached --name-only
$ git diff --cached 
$ git merge --abort


---:---:---
go_602_0010 go(lang) in docker
##go ##golang

# golang in docker (example 1)
> docker run -i -t -v C:/projects/go:/go -p 8080:8080 --name golang golang
> docker start -i golang

$ go version
$ go get github.com/golang/example/hello/...
$ go run github.com/golang/example/hello
$ go run github.com/golang/example/outyet
$ export GOOS=windows GOARCH=amd64
$ go install github.com/golang/example/hello


# golang in docker (example 2)
> docker run --rm -v "%CD%:/usr/src/sendtoeds" -w /usr/src/sendtoeds -e GO -e GOOS=windows -e GOARCH=amd64 golang bash -c "go get -d -v ./... && go fmt && go build -v"
> docker run --rm -i -t -v "%CD%:/usr/src/sendtoeds" -w /usr/src/sendtoeds -e GO -e GOOS=windows -e GOARCH=amd64 golang bash
> docker run --rm -it -p 8080:8080 -v "%CD%:/usr/src/publisher" -w /usr/src/publisher -e GOOS=linux -e GOARCH=amd64 golang bash -c "go get -d -v ./... && go fmt && go run publisher.go -port=8080 -phob=0YAy.TaLp.SVTr -phan=XhfN.DQ35.4R4t"



---:---:---
go_603_0100 c# dotnet commands
##dotnetrun

# .NET Command: format source code

$ dotnet tool install -g dotnet-format
$ dotnet format --dry-run --check
$ echo $?

> dotnet tool install -g dotnet-format
> dotnet format --dry-run --check
> Write-Host $LastExitCode


---:---:---
go_603_1000 c# dotnet programming
go_603_1010 c# dotnet programming: Refresh ASP.NET Core MVC view without reloading the application

# credits
$ start https://dev.to/alexzeitler/refresh-asp-net-core-website-without-reloading-application-2ffo

# add this NuGet package to the project: Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation
$ dotnet add package 'Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation'

# in Startup.cs change this line:
<- `services.AddControllersWithViews();`
-> `services.AddControllersWithViews().AddRazorRuntimeCompilation();`



---:---:---
go_604_0000 java
go_604_0100 java commmands
go_604_0200 java Lego Mindstorm
##mindstorm

# Lego Mindstorm: first program
> start http://www.lejos.org/nxt/nxj/tutorial/Preliminaries/FirstProgram.htm

> nxjc HelloWorld.java
> nxjlink -o HelloWorld.nxj HelloWorld
> nxjupload -r HelloWorld.nxj

> nxjc HelloWorld.java
> nxj -r -o HelloWorld.nxj HelloWorld



---:---:---
go_604_1000 java programming


---:---:---
go_605_0000 javascript

---:---:---
go_605_1000 javascript programming

---:---:---
go_605_1000 javascript programming: sleep

# credits 
$ start https://stackoverflow.com/a/39914235/13860643

# sleep for 5 seconds
> await new Promise(r => setTimeout(r, 2000));

# sleep() function + demo
```
function sleep(ms) {
  return new Promise(resolve => setTimeout(resolve, ms));
}

async function demo() {
  console.log('taking a break for 5 seconds ...');
  await sleep(5000);
  console.log('now showing sleep in a loop...');

  for (let i = 0; i < 10; i++) {
    await sleep(2000);
    console.log(i);
  }
}

demo();
```

---:---:---
go_701_0000 mysql
## mysql

---:---:---
go_701_0001 mysql: manage users

# list users
> use mysql;
> SELECT User, Host FROM user ORDER BY User;

# create user
> CREATE USER 'db_user'@'localhost' IDENTIFIED BY 'my.secret.password';
> CREATE USER 'db_user'@'localhost' IDENTIFIED WITH mysql_native_password BY 'my.secret.password';

# (re)set password of user
> SET PASSWORD FOR 'db_user'@'localhost' = 'yet.very.secret.password';

# change user
> ALTER USER 'db_user'@'localhost' IDENTIFIED WITH mysql_native_password BY 'my.secret.password';

# delete user
> DROP USER 'microstaxx'@'localhost';

# show privileges 
> SHOW GRANTS FOR ticket_prd;

# grant privileges
> GRANT ALL PRIVILEGES ON app_db.* TO 'db_user'@'localhost';
> GRANT USAGE ON app_db.* TO 'db_user'@'localhost';
> GRANT SELECT, LOCK TABLES ON app_db.* TO 'db_user'@'localhost';

---:---:---
go_701_0002 mysql: change the default collation

# How to change the default collation (and default character set) of a database?
$ start https://stackoverflow.com/questions/5906585/how-to-change-the-default-collation-of-a-database

# change collation to latin1
> ALTER DATABASE app_db CHARACTER SET latin1 COLLATE latin1_german2_ci;

# change database / tables to utf8
> use app_db;
> ALTER DATABASE app_db CHARACTER SET utf8 COLLATE utf8_unicode_ci;
> ALTER TABLE table_1 CHARACTER SET utf8 COLLATE utf8_unicode_ci;
> ALTER TABLE table_2 CHARACTER SET utf8 COLLATE utf8_unicode_ci;
> ALTER TABLE table_3 CHARACTER SET utf8 COLLATE utf8_unicode_ci;
> ALTER TABLE table_4 CHARACTER SET utf8 COLLATE utf8_unicode_ci;

> ALTER TABLE app_db.table_1 MODIFY colum_1 text CHARACTER SET utf8 COLLATE utf8_unicode_ci;

---:---:---
go_701_0003 mysql: store encrypted login on file system

# set login (via cmd)
> "C:\Program Files\MySQL\MySQL Server 8.0\bin\mysql_config_editor.exe" set --login-path db_user --host=db_host --user=db_user --password

# set login (via powershell)
> & 'C:\Program Files\MySQL\MySQL Server 8.0\bin\mysql_config_editor.exe' set --login-path db_user --host=db_host --user=db_user --password

# set login (via bash)
$ mysql_config_editor set --login-path db_user --host=db_host --user=db_user --password

# list all logins
$ mysql_config_editor print --all

# login to mysql
$ mysql --login-path=db_user

---:---:---
go_701_0004 mysql: dump database

# dump mysql database
$ mysqldump -u root -p --skip-opt --default-character-set=utf8 --single-transaction --no-tablespaces --comments --hex-blob --dump-date --no-autocommit --add-drop-database --databases app_db > app_db-latest.sql

# import exported data
$ echo 'source app_db-latest.sql' | mysql -u root -p --default-character-set=utf8 app_db'



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go_800_0010 raspberry pi raspi

# (1) write image to SSD-card
$ start https://www.raspberrypi.org/downloads/

# (3) on your raspi: change configuration
# -> Localisation Options
# ... set keyboard, time zone and Wifi to DE
# -> Interface Options -> SSH
# ... enable SSH
$ sudo raspi-config



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go_900_0000 misc