A basic redirect from one website to another:

<meta http-equiv="refresh" content="0; URL=https://www.trembl.org" />

• content is the dealy in milliseconds
• URL is the target url

Making a copy of a website with wget should work like that:

wget -r mywebsite.com

-r recursively crawls the site, default is until level 5.

With filenames with non-latin characters, wget is not happy:

bash Incomplete or invalid multibyte sequence encountered Incomplete or invalid multibyte sequence encountered Incomplete or invalid multibyte sequence encountered Incomplete or invalid multibyte sequence encountered

That seems to be a bug in wget.

Workaround

wget -r --restrict-file-names=nocontrol mywebsite.com

Resizing Movies with ffmpeg

Scaling down Full HD from 1920x1080 to 960x540:

ffmpeg -i input.mp4 -s 960x540 -c:a copy output.mp4

-i ... input
-s ... scale
-c ... codec

Compressing with H.2645

ffmpeg -i input.mp4 -vcodec libx265 -crf 28 output.mp4

crf ... video quality, lower value means better quality

Testing network speed on macOS:

networkQuality

Example output:

Downlink: capacity 24.052 Mbps, responsiveness 321 RPM - Uplink: capacity 0.000
Downlink: capacity 24.052 Mbps, responsiveness 294 RPM - Uplink: capacity 20.669
Downlink: capacity 24.548 Mbps, responsiveness 250 RPM - Uplink: capacity 20.669
Downlink: capacity 24.548 Mbps, responsiveness 248 RPM - Uplink: capacity 17.763
Downlink: capacity 26.099 Mbps, responsiveness 243 RPM - Uplink: capacity 17.763
Downlink: capacity 26.099 Mbps, responsiveness 243 RPM - Uplink: capacity 16.716
Downlink: capacity 26.567 Mbps, responsiveness 240 RPM - Uplink: capacity 16.716
Downlink: capacity 26.567 Mbps, responsiveness 240 RPM - Uplink: capacity 16.632
Downlink: capacity 27.436 Mbps, responsiveness 237 RPM - Uplink: capacity 16.632
Downlink: capacity 27.436 Mbps, responsiveness 235 RPM - Uplink: capacity 15.908
Downlink: capacity 27.120 Mbps, responsiveness 194 RPM - Uplink: capacity 15.908
Downlink: capacity 27.120 Mbps, responsiveness 185 RPM - Uplink: capacity 16.711
Downlink: capacity 25.164 Mbps, responsiveness 156 RPM - Uplink: capacity 16.711
Downlink: capacity 25.164 Mbps, responsiveness 150 RPM - Uplink: capacity 16.939
Downlink: capacity 24.892 Mbps, responsiveness 124 RPM - Uplink: capacity 16.939
Downlink: capacity 24.892 Mbps, responsiveness 118 RPM - Uplink: capacity 17.627
Downlink: capacity 23.011 Mbps, responsiveness 108 RPM - Uplink: capacity 17.627
Downlink: capacity 23.011 Mbps, responsiveness 100 RPM - Uplink: capacity 15.339
Downlink: capacity 22.093 Mbps, responsiveness 87 RPM - Uplink: capacity 15.339
Downlink: capacity 22.093 Mbps, responsiveness 85 RPM - Uplink: capacity 13.592
Downlink: capacity 23.291 Mbps, responsiveness 63 RPM - Uplink: capacity 13.592
Downlink: capacity 23.291 Mbps, responsiveness 63 RPM - Uplink: capacity 14.177
Downlink: capacity 23.291 Mbps, responsiveness 43 RPM - Uplink: capacity 17.627 
==== SUMMARY ====
Uplink capacity: 17.627 Mbps
Downlink capacity: 23.291 Mbps
Responsiveness: Low (43 RPM)
Idle Latency: 19.708 milliseconds

This is mainly used for troubleshooting POP3 connections, to check if the connection/server/password actually works. Also possible to read emails that way, but very ~1995ish. If you really, really want to (re-) experience that experience, check out alpine, the sucessor of pine.

Start connection with OpenSSL:

openssl s_client -connect yourusername.yourmailserver:995

This is non-quiet, resulting in a lot of talkback, most importantly:

    ...
    Start Time: 1693034257
    Timeout   : 7200 (sec)
    Verify return code: 0 (ok)
    Extended master secret: no
    Max Early Data: 0
---
read R BLOCK
+OK Dovecot ready.

+OK Dovecot ready. tells use the mail programme - in this case Dovecot - is ready, waiting for user & password input.

user youremailaddress
+OK
pass yourpassword
+OK Logged in.

The stat command tells you how many message, and how large they are.

stat
+OK 2 9394

Ok, two message, totalling 9394 bytes. To read it, use the retrive command, specifiying the number of the message you want to read.

retr 1

This will display the whole message, including any and all headers.

Situation

Your directory on your Apache Server does not have an index.html and creates a 404 when visited. But there are files in the directory, that should be displayed.

Solution

Create a .htaccess file and add the following line:

Options +Indexes

This only works, if AllowOverride Options is set to true in your Apache Settings.

Mac, Terminal

Open screen with log flag, address & baud rate

screen -L /dev/tty.usbmodem14101 9600

End the session with: ^a - k (press control+a, release, then press k)

Screenshots to follow

Concatenating videos with the Quicktime Player requires unnecessary decoding/encoding, with takes time and computational resources.

Solution: Concatente Files von FFMPEG

https://trac.ffmpeg.org/wiki/Concatenate

Using ffmpeg

1. Create a list: mylist.txt

   file '/path/to/file1.mp4'
   file '/path/to/file2.mp4'
   file '/path/to/file3.mp4'

2. Run ffmpeg ffmpeg -f concat -i mylist.txt -c copy output.mp4

Troubleshooting

[concat @ 0x7fc407904080] Unsafe file name '2008-08-05 21_38_08.mov' mylist.txt: Operation not permitted

Filenames should not have spaces, escape them with \.

This is a short, condensed instruction how to set-up command-line access to github.com. Written is response to onboard new FabAcademy students - and get them started with MkDocs.

This guides is for macOS 12 or higher. My Mac uses macOS Ventura 13.0.01.

Step 1: Creating a new SSH Key

Go to the .ssh directory.

$ cd ~/.ssh

Made new key:

$ ssh-keygen -t ed25519 -C "your_email@example.com"

• Don't just copy, put in your email. I also added a password.
• Also, don't copy the $, just the ssh-keygen -t ed25519 -C "your_email@example.com" part. But with your email.

You can name your key. For this example, we call it id_github_test.

Step 2: Adding SSH Key to ssh-agent.

$ eval "$(ssh-agent -s)"

Step 3: Adding Key Info to config

Open .ssh/config in your favourite text editor. If you want to stay at the command line, use nano.

Add the following:

Host *.github.com
  AddKeysToAgent yes
  UseKeychain yes
  IdentityFile ~/.ssh/id_github_test

Step 4: Adding the Key to ssh-agent

Adding private key to ssh-agent

$ ssh-add --apple-use-keychain ~/.ssh/id_github_test

This add the new key to the Apple Keychain.

If you used a passphrase when you created the key, you will be asked for it now.

Enter passphrase for /Users/georg/.ssh/id_github_test: 

Identity added: /Users/georg/.ssh/id_github_test (your_email@example.com)

Step 5: Adding Public Key to github.com

• Log into Github
• Profile > Settings > SSH and GPG Keys
• Click 'New SSH Key'

Copy and paster your public key, in this example case, id_github_test.pub.

The tutorial on Github suggest to copy the public key using a command:

$ pbcopy < ~/.ssh/id_github_test.pub      

pbcopy - for paste board copy is the terminal interface to the macOS' Copy & Paste. pbcopy < read the content of a file into the copy memory. After running pbcopy you can press Command-V to paste the text.

• Paste the copied SSH Public Key.

Step 5.1: Two-Factor Authentication at GitHub.com

I setup Two-Factor Authentication at GitHub.com, I had to confirm the addition of a new key via my mobile GitHub App. Your mileage might vary.

Step 6: Testing the connection

$ ssh -T git@github.com
Hi trembl! You've successfully authenticated, 
but GitHub does not provide shell access.

Ok, great! It worked!

Now you can clone, add, commit, push and pull!

Sources:

• Github CLI
• Adding a new SSH key to your GitHub account

This warning is pretty self- explanatory:

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@         WARNING: UNPROTECTED PRIVATE KEY FILE!          @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
Permissions 0644 for '/Users/georg/.ssh/my_rsa_key' are too open.
It is required that your private key files are NOT accessible by others.
This private key will be ignored.

Solution

Limit the key to read/write access by the user only:

chmod 600 ~/.ssh/my_rsa_key

It's also possible to make it only readable by the user, but then you need to chmod every time you want to update/change it.

chmod 400 ~/.ssh/my_rsa_key

Sources: StackOverflow