main

Author: sharpchen

docs/document/Articles/docs/SSH Quick Start.md

@@ -0,0 +1,74 @@
+# OpenSSH Quick Start
+
+## The Authentication
+
+A host machine that running a SSH server can be called as **Remote** which should store *public keys* for client hosts.
+A host machine(client) attempting to connect with Remote should know a *private key* and *passphrase*.
+This is how the authentication happen:
+
+1. Client sends request to Remote.
+2. If the Client had never connect to the Remote, warning prompts to confirm connection implying it may be dangerous.
+3. If any public key on Remote matches the client, Remote requests the client for authenticator which should be calculated by *passphrase* and *private key*
+4. User enter the *passphrase* to decrypt the private key, SSH auto-calculates the authenticator, then send it to the Remote.
+
+## Client Side
+
+- Generate public key for connecting **one or more** remotes by `ssh-keygen`
+```sh
+ssh-keygen -t rsa
+```
+- Register new public key to remote by `ssh-copy-id`(may require login on remote)
+```sh
+# add public key under `~/.ssh/` to `~/.ssh/authorized_keys` on <remote>
+ssh-copy-id -i <pub_key_file> [<username>@]<remote>
+```
+- Managing authenticated state and **agent forwarding** by `ssh-agent`
+```sh
+ssh-agent $SHELL
+```
+- Add private key to `ssh-agent` to memorize the state of the key by `ssh-add`
+```sh
+ssh-add ~/.ssh/id_ed25519
+ssh-add -l # list all private keys memorized by ssh-agent
+ssh-add -d id_ed25519 # inform ssh-agent to forget this key
+ssh-add -D # forget all keys
+```
+- Managing once connected remote in `~/.ssh/known_hosts`
+- File transfer by `scp`
+- Modify *passphrase* by `ssh-keygen` if you forgot
+```sh
+ssh-keygen -p 
+```
+
+## Server Side
+
+- Start SSH server by `sshd`
+- Manage SSH server config by `/etc/ssh/sshd_config`
+- Manage public key for multiple clients in `~/.ssh/authorized_keys`
+> [!NOTE]
+> Besides `ssh-copy-id`, you can directly edit `~/.ssh/authorized_keys` to add new public key for a client.
+
+
+## Create Key Pair
+
+```sh
+ssh-keygen [-t <type>] [-f <path>] [-N <passphrase>] [-C <comment>]
+```
+
+- `-t`: specify key type, `ed25519` by default.
+- `-f`: output fullname of the key, public key will have extra extension `.pub`. `ssh-keygen` will prompt for it if not specified anyway.
+- `-N`: specify passphrase, will ask anyway if unspecified. This may expose your passphrase to command history.
+- `-C`: comment for identifying the key.
+
+> [!NOTE]
+> see `man ssh-keygen`
+
+## Re-encrypt Key
+
+You might want to encrypt the keys with different type and passphrase, as well as a new name.
+
+```sh
+ssh-keygen -p [-t <type>] [-f <path>] [-P <old_passphrase>] [-N <new_passphrase>]
+```
+
+Similar to creating a key pair, you don't have to fill all options, leave them empty and let the cli prompt for you.

docs/document/Articles/docs/Setup nix-on-droid.md

@@ -0,0 +1,86 @@
+# Setup nix-on-droid
+
+## Prerequisites
+
+- Root privilege on you android phone(it's not stable in devices without root)
+- nix-on-droid installed.
+- Optional: `adb`, `pwsh`
+    You can use `adb` to type inputs from your computer connected with your android device. 
+    The following powershell function solves the escape problem of `adb shell input text`, so you don't have to escape manually.
+    ```ps1
+    # Use -Enter to press enter after command input
+    function adbin([string]$Str, [switch]$Enter) {
+        $special = @( ' ', '\|', '\$', '&', '\(', '\)', '~','\*', "\'",'"','<','>')
+        foreach ($char in $special) {
+            $Str = $Str -replace $char, ($char.Length -gt 1 ? $char : "\$char")
+        }
+        adb shell input text $Str
+        if ($Enter) {
+            adb shell input keyevent KEYCODE_ENTER
+        }
+    }
+    ```
+    > [!NOTE]
+    > You can wrap the same as bash function by `awk` or other text manipulation tools.
+
+
+## Init
+
+- nix-on-droid may ask for url for certain file, if the url is not accessible on your phone, download it and transfer to your phone. And replace the default url as `file:///sdcard/...`
+- type `yes` when nix prompt for downloads for first init.
+- add and update channels: 
+    ```sh
+    nix-channel --add https://github.com/nix-community/home-manager/archive/release-24.05.tar.gz home-manager && channel
+    ```
+    > [!TIP]
+    > If you use the wrapper function mentioned above, would be like this:
+    >```ps1
+    >adbin -Enter 'nix-channel --add https://github.com/nix-community/home-manager/archive/release-24.05.tar.gz home-manager'
+    >```
+
+## Connect to nix-on-droid
+
+- Install `openssh`
+
+```sh
+nix profile install nixpkgs#openssh
+```
+
+- create a empty `ssh_config`, `sshd` requires at least one specified. We don't specify any option in it in this guide but it's needed afterward.
+
+```sh
+mkdir -p /etc/ssh/ && touch /etc/ssh/sshd_config
+```
+
+- generate a host key for nix-on-droid, change the key type and passphrase as you like, they don't make too much difference.
+
+```sh
+ssh-keygen -t rsa -b 4096 -f ssh_host_rsa_key -N "" # key is generated in pwd
+```
+
+- create `~/.ssh/authorized_keys` and paste your public key from your computer(`gc ~/.ssh/<name>.pub`) to this file.
+
+```sh
+mkdir -p ~/.ssh/ && touch ~/.ssh/authorized_keys && echo <pub> >> ~/.ssh/authorized_keys
+```
+
+- start ssh daemon by `sshd`
+
+```sh
+sshd -p <port> -h <host_key> -d
+```
+
+`-d` is essential to know whether your port is been taken or not. See details in `man sshd`.
+
+- now connect to nix-on-droid from your computer
+
+```ps1
+ssh -l nix-on-droid -p <port> <ipaddr_of_phone>
+```
+
+> [!NOTE]
+> `<ipaddr_of_phone>` can be inspected from your `Settings - About phone`
+
+## Final Step
+
+Finally you can type everything in your computer through SSH! So use nix as you like.

…rShell/docs/File System/4.Create Item.md …ll/docs/File System/4.Manipulate Item.mddocs/document/PowerShell/docs/File System/4.Create Item.md renamed to docs/document/PowerShell/docs/File System/4.Manipulate Item.md docs/document/PowerShell/docs/File System/4.Create Item.md renamed to docs/document/PowerShell/docs/File System/4.Manipulate Item.md

@@ -1,4 +1,5 @@
-# Create Item
+# Manipulate Item
+## Create Item
 
 Powershell uses a single cmdlet named `New-Item` to represent all kinds of creation logic for file system items like folder, file, symlinks...
 
@@ -24,7 +25,7 @@ New-Item <file_path>
 > [!TIP]
 > Use `-Force` flag to overwrite existing target.
 
-## Directory
+### Directory
 
 ```ps1
 New-Item <dir_path> -ItemType Directory
@@ -41,19 +42,38 @@ mkdir <dir_path>
 > [!TIP]
 > Use `-Force` flag to overwrite existing target.
 
-## Symbolic Link
+### Symbolic Link
 
 ```ps1
 New-Item <symlink_path> -Target <source> -ItemType SymbolicLink
 ```
 
+> [!NOTE]
+> `-Target` is an alias of `-Value`
+
 > [!TIP]
 > Use `-Force` flag to overwrite existing target.
 
-## Ignore Wildcards
+### Ignore Wildcards
 
 `-Path` translates wildcards by default, if you do need to include special characters from wildcards syntax for your new item, use `-LiteralPath`.
 
 ```ps1
 New-Item -LiteralPath 'foo*.txt' # creates a file literally named `foo*.txt`
 ```
+
+## Delete
+
+- delete file
+
+```ps1
+ri <file>
+```
+
+- delete folder
+
+```ps1
+ri -rec -force <folder>
+```
+
+### Rename

docs/document/PowerShell/docs/File System/6. Inspect File System.md

@@ -0,0 +1,23 @@
+# Inspect File System
+
+## List Items
+
+- Recursively
+
+```ps1
+gci -rec
+```
+
+- Include Hidden Items
+
+```ps1
+gci -force
+```
+
+## Size
+
+- Directory Size
+
+```ps1
+gci -file -rec -force | measure { $_.Length / 1MB } -Sum
+```

docs/document/PowerShell/docs/File System/6.Inspect File System.md

@@ -57,6 +57,9 @@ $foo['Name'] # foo
 $foo['Name', 'Age'] # @('foo', 18)
 ```
 
+> [!NOTE]
+> PowerShell uses `TryGetValue` when accessing value with indexer syntax for `IDictionary` types, so it never throw.
+
 `.` accessor would also works **as long as there's no duplicated Extended Property with the same name of the key you passed.**
 
 ```ps1

docs/document/PowerShell/docs/Language/HashTable.md

@@ -35,6 +35,9 @@ gci | measure -Property Length -Sum -Max
 # -Property is positional
 gci | measure Length -Sum -Max
 
+# measure different properties with same rule
+gps | measure VM,ID -Sum -Max
+
 # Calculate Max in unit GB
 gci | measure { $_.Length / 1GB } -Max 
 ```

…hell/docs/Object Manipulation/Compare.md …ll/docs/Object Manipulation/1.Compare.mddocs/document/PowerShell/docs/Object Manipulation/Compare.md renamed to docs/document/PowerShell/docs/Object Manipulation/1.Compare.md docs/document/PowerShell/docs/Object Manipulation/Compare.md renamed to docs/document/PowerShell/docs/Object Manipulation/1.Compare.md

@@ -33,5 +33,15 @@ gci -file | where Extension -eq '.ps1'
 gci -file | where { $_.Extension -eq '.ps1' }
 ```
 
-> [!NOTE]
-> See: `help where`
+## Intrinsic Where
+
+Intrinsic `Where` can be useful when performance matters, it provides a way to return early base on certain condition without consuming the whole iteration.
+
+- First or Last items satisfy certain condition
+- Skip until one satisfies the condition and return all remaining items(including the one satisfies)
+- Return items until one not satisfies the condition(excluding the one satisfies)
+- Split items into two collections, one contains items satisfied the condition, the another are items remained.
+
+```cs
+Where(scriptblock condition, WhereOperatorSelectionMode mode = 0, int? count)
+```