### Full assh Configuration Example (YAML)

Source: https://github.com/moul/assh/blob/master/README.md

This comprehensive YAML snippet illustrates the structure of a typical `~/.ssh/assh.yml` file. It includes sections for defining `hosts` with various options (Hostname, User, Port, Gateways, Inherits, Aliases, RateLimit, ResolveCommand), reusable `templates`, global `defaults` (ControlMaster, ControlPath, ControlPersist, Port, User, Hooks), and `includes` for modularity. It showcases inheritance, templating, gateway configurations, dynamic host resolution, and various hook examples within the defaults section.

```yaml
hosts:

  homer:
    # ssh homer ->  ssh 1.2.3.4 -p 2222 -u robert
    Hostname: 1.2.3.4
    User: robert
    Port: 2222

  bart:
    # ssh bart ->   ssh 5.6.7.8 -u bart           <- direct access
    #            or ssh 5.6.7.8/homer -u bart     <- using homer as a gateway
    Hostname: 5.6.7.8
    User: bart
    Gateways:
    - direct                   # tries a direct access first
    - homer                    # fallback on homer gateway

  maggie:
    # ssh maggie ->   ssh 5.6.7.8 -u maggie       <- direct access
    #              or ssh 5.6.7.8/homer -u maggie   <- using homer as a gateway
    User: maggie
    Inherits: bart             # inherits rules from "bart"

  bart-access:
    # ssh bart-access ->  ssh home.simpson.springfield.us -u bart
    Inherits:
    - bart-template
    - simpson-template

  lisa-access:
    # ssh lisa-access ->  ssh home.simpson.springfield.us -u lisa
    Inherits:
    - lisa-template
    - simpson-template

  marvin:
    # ssh marvin    -> ssh marvin    -p 23
    # ssh sad-robot -> ssh sad-robot -p 23
    # ssh bighead   -> ssh bighead   -p 23
    # aliases inherit everything from marvin, except hostname
    Port: 23
    Aliases:
    - sad-robot
    - bighead

  dolphin:
    # ssh dolphin   -> ssh dolphin -p 24
    # ssh ecco      -> ssh dolphin -p 24
    # same as above, but with fixed hostname
    Port: 24
    Hostname: dolphin
    Aliases: ecco
    RateLimit: 10M # 10Mbytes/second rate limiting

  schooltemplate:
    User: student
    IdentityFile: ~/.ssh/school-rsa
    ForwardX11: yes

  schoolgw:
    # ssh school ->   ssh gw.school.com -l student -o ForwardX11=no -i ~/.ssh/school-rsa
    Hostname: gw.school.com
    ForwardX11: no
    Inherits: schooltemplate

  "expanded-host[0-7]*":
    # ssh somehost2042 ->       ssh somehost2042.some.zone
    Hostname: "%h.some.zone"

  "*.shortcut1":
    ResolveCommand: /bin/sh -c "echo %h | sed s/.shortcut1/.my-long-domain-name.com/"

  "*.shortcut2":
    ResolveCommand: /bin/sh -c "echo $(echo %h | sed s/.shortcut2//).my-other-long-domain-name.com"

  "*.scw":
    # ssh toto.scw -> 1. dynamically resolves the IP address
    #                 2. ssh {resolved ip address} -u root -p 22 -o UserKnownHostsFile=null -o StrictHostKeyChecking=no
    # requires github.com/scaleway/scaleway-cli
    ResolveCommand: /bin/sh -c "scw inspect -f {{.PublicAddress.IP}} server:$(echo %h | sed s/.scw//)"
    User: root
    Port: 22
    UserKnownHostsFile: /dev/null
    StrictHostKeyChecking: no

  my-env-host:
    User: user-$USER
    Hostname: ${HOSTNAME}${HOSTNAME_SUFFIX}

templates:
  # Templates are similar to Hosts; you can inherit from them
  # but you cannot ssh to a template
  bart-template:
    User: bart
  lisa-template:
    User: lisa
  simpson-template:
    Host: home.simpson.springfield.us

defaults:
  # Defaults are applied to each hosts
  ControlMaster: auto
  ControlPath: ~/tmp/.ssh/cm/%h-%p-%r.sock
  ControlPersist: yes
  Port: 22
  User: bob
  Hooks:
    # Automatically backup ~/.ssh/config
    BeforeConfigWrite:
      - 'exec set -x; cp {{.SSHConfigPath}} {{.SSHConfigPath}}.bkp'

    AfterConfigWrite:
      # Concat another `ssh_config` file with the one just generated by `assh`
      - 'exec cat ~/.ssh/my-heroku-generated-config >> {{.SSHConfigPath}}'

      # Alert me with a Desktop notification
      - notify "{{.SSHConfigPath}} has been rewritten"

    OnConnect:
      # Log internal information to a file
      - exec printf '{{.}}' | jq . >> ~/.ssh/last_connected_host.txt

      # Alert me with a Desktop notification
      - notify New SSH connection to {{.Host.Prototype}} at {{.Stats.ConnectedAt}}

      # Write the host prototype to the terminal stderr
      - write New SSH connection to {{.Host.Prototype}}

    OnDisconnect:
      # write on terminal and in a Desktop notification some statistics about the finished connection
      - "write  SSH connection to {{.Host.HostName}} closed, {{.Stats.WrittenBytes }} bytes written in {{.Stats.ConnectionDuration}} ({{.Stats.AverageSpeed}}bps)"
      - "notify SSH connection to {{.Host.HostName}} closed, {{.Stats.WrittenBytes }} bytes written in {{.Stats.ConnectionDuration}} ({{.Stats.AverageSpeed}}bps)"

includes:
- ~/.ssh/assh.d/*.yml
- /etc/assh.yml
- $ENV_VAR/blah-blah-*/*.yml

ASSHBinaryPath: ~/bin/assh  # optionally set the path of assh
```

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

### Building assh Config File (Console)

Source: https://github.com/moul/assh/blob/master/README.md

This console snippet provides an example of using the `assh config build` command. This command processes the `assh.yml` configuration and outputs the generated SSH configuration to standard output, which is then redirected to overwrite the user's `~/.ssh/config` file.

```console
$ assh config build > ~/.ssh/config
```

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

### Defining SSH Hosts and Gateways in assh YAML Config

Source: https://github.com/moul/assh/blob/master/README.md

Provides an example assh.yml configuration file defining hosts, their hostnames, and gateway relationships. Demonstrates simple direct connections, single-gateway connections, and chained gateway connections, including a fallback mechanism using 'direct'.

```yaml
hosts:\n  hosta:\n    Hostname: 1.2.3.4\n\n  hostb:\n    Hostname: 5.6.7.8\n    Gateways: hosta\n\n  hostc:\n    Hostname: 9.10.11.12\n    Gateways: hostb\n\n  hostd:\n    Hostname: 13.14.15.16\n    GatewayConnectTimeout: 2\n    Gateways:\n    - direct\n    - hosta
```

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

### Configuring OnConnect Exec Hook in assh YAML

Source: https://github.com/moul/assh/blob/master/README.md

Shows how to configure an assh hook using the 'exec' driver in the YAML configuration. This example uses the OnConnect event to execute a shell command (echoing host details and piping to jq) upon a successful connection, demonstrating the use of Golang template variables within the command.

```yaml
defaults:\n  Hooks:\n    OnConnect: exec echo '{{.Host}}' | jq .
```

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

### Using assh for Simple SSH Gateway (Command Line)

Source: https://github.com/moul/assh/blob/master/README.md

Demonstrates connecting to a host via a single gateway using assh's simplified syntax. Includes the equivalent standard OpenSSH command for comparison.

```console
$ ssh hosta/hostb\nuser@hosta $
```

```console
$ ssh -o ProxyCommand="ssh hostb nc %h %p" hosta
```

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

### Using assh for Chained SSH Gateways (Command Line)

Source: https://github.com/moul/assh/blob/master/README.md

Illustrates connecting to a host through multiple chained gateways using assh's concise syntax. Shows the complex equivalent standard OpenSSH command required.

```console
$ ssh hosta/hostb/hostc\nuser@hosta $
```

```console
$ ssh -o ProxyCommand="ssh -o ProxyCommand='ssh hostc nc %h %p' hostb nc %h %p" hosta
```

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

### Displaying assh CLI Usage (Console)

Source: https://github.com/moul/assh/blob/master/README.md

This console snippet shows the basic command-line usage of the `assh` tool. It lists the available commands (`ping`, `info`, `config`, `sockets`, `help`) and global options for controlling behavior like configuration file location, debug mode, and verbosity.

```console
NAME:
   assh - advanced ssh config

USAGE:
   assh [global options] command [command options] [arguments...]

VERSION:
2.8.0 (HEAD)

AUTHOR(S):
   Manfred Touron <https://github.com/moul/assh>

COMMANDS:
   ping          Send packets to the SSH server and display statistics
   info          Display system-wide information
   config        Manage ssh and assh configuration
   sockets       Manage control sockets
   help, h       Shows a list of commands or help for one command

GLOBAL OPTIONS:
  --config value, -c value       Location of config file (default: "~/.ssh/assh.yml") [$ASSH_CONFIG]
  --debug, -D                    Enable debug mode [$ASSH_DEBUG]
  --verbose, -V                  Enable verbose mode
  --help, -h                     show help
  --version, -v                  print the version
```

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

### Configuring BeforeConfigWrite Hook (YAML)

Source: https://github.com/moul/assh/blob/master/README.md

This YAML snippet demonstrates a hook (`BeforeConfigWrite`) that runs just before assh rewrites the `~/.ssh/config` file. It uses the `exec` driver to execute a command that creates a backup copy of the existing config file.

```yaml
defaults:
  Hooks:
    BeforeConfigWrite: exec cp {{.SSHConfigPath}} {{.SSHConfigPath}}.backup
# make a copy of ~/.ssh/config before being rewritten
```

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

### Using Write Driver OnConnect (YAML)

Source: https://github.com/moul/assh/blob/master/README.md

This YAML snippet illustrates the use of the `write` driver within an `OnConnect` hook. The `write` driver sends the specified string, interpreted as a Golang template, to the standard output (terminal) when a connection is established.

```yaml
defaults:
  Hooks:
    OnConnect:
    - write New SSH connection to {{.Host.Prototype}}.
# writes: "New SSH connection to moul@127.0.0.1:22." on the terminal on connection
```

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

### Using Notify Driver OnConnect (YAML)

Source: https://github.com/moul/assh/blob/master/README.md

This YAML snippet shows the configuration for the `notify` driver in an `OnConnect` hook. This driver sends a desktop notification upon establishing an SSH connection, using the provided string as the notification message, which is parsed as a Golang template.

```yaml
defaults:
  Hooks:
    OnConnect: notify New SSH connection to {{.Host.Prototype}}.
```

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

### Processing assh Output with jq (Shell)

Source: https://github.com/moul/assh/blob/master/README.md

Demonstrates how assh can output internal data (like a host's parsed configuration) as JSON, which can then be piped to tools like `jq` for pretty printing or further processing. This shows the structured nature of assh's internal data.

```shell
# executes: `echo '{"HostName":"localhost","Port":"22","User":"moul","ControlPersist":"yes",...}' | jq .
# which results in printing a pretty JSON of the host
# {
#   "HostName": "localhost",
#   "Port": "22",
#   "User": "moul",
#   "ControlPersist": "yes",
#   ...
# }
```

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

### Configuring OnConnect Hook with exec (YAML)

Source: https://github.com/moul/assh/blob/master/README.md

This YAML snippet shows how to configure a hook that executes a shell command when an SSH connection is established (`OnConnect`). It uses the `exec` driver to pipe a message about the connection prototype to the `mail` command, sending an email.

```yaml
defaults:
  Hooks:
    OnConnect: exec echo 'New SSH connection to {{.Host.Prototype}}.' | mail -s "SSH connection journal" m+assh@42.am
# send an email with the connection prototype
```

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

### Executing Background Hook (YAML)

Source: https://github.com/moul/assh/blob/master/README.md

This YAML snippet shows how to run a command in the background using the `exec` driver within an `OnConnect` hook. Appending `&` to the command makes it non-blocking, allowing the SSH connection to proceed while the hooked process runs independently.

```yaml
defaults:
  Hooks:
    OnConnect:
    - exec sleep 60 &
# execute the `sleep 60` command in background (non-blocking)
# if you quit your ssh connection, the process will continue in background.
```

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

### Using Notify Driver OnDisconnect (YAML)

Source: https://github.com/moul/assh/blob/master/README.md

This YAML snippet demonstrates using the `notify` driver within an `OnDisconnect` hook. It triggers a desktop notification when an SSH connection closes, displaying statistics about the connection duration, written bytes, and average speed.

```yaml
defaults:
  Hooks:
    OnDisconnect:
    - "notify SSH connection to {{.Host.Name}} closed, {{ .Stats.WrittenBytes }} bytes written in {{ .Stats.ConnectionDuration }} ({{ .Stats.AverageSpeed}})"
```

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

### Appending Date to Config After Write Hook (YAML)

Source: https://github.com/moul/assh/blob/master/README.md

This YAML snippet configures an `AfterConfigWrite` hook, executed after assh has written the new `~/.ssh/config` file. It uses the `exec` driver to append a comment containing the current date to the generated configuration file.

```yaml
defaults:
  Hooks:
    AfterConfigWrite: 'exec echo "# date: `date`" >> {{.SSHConfigPath}}'
# Append a comment with the compilation date to the generated ~/.ssh/config file
```

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

### Appending External Config After Write Hook (YAML)

Source: https://github.com/moul/assh/blob/master/README.md

This YAML snippet demonstrates another use of the `AfterConfigWrite` hook. It utilizes the `exec` driver to concatenate the content of another external SSH configuration file (`/path/to/my/provider/generated/.ssh/config`) onto the end of the `~/.ssh/config` file generated by assh.

```yaml
defaults:
  Hooks:
  AfterConfigWrite: 'exec cat /path/to/my/provider/generated/.ssh/config >> {{.SSHConfigPath}}'
# Append another .ssh/config file to the generated .ssh/config file
```

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

### Using Write Driver OnDisconnect (YAML)

Source: https://github.com/moul/assh/blob/master/README.md

This YAML snippet demonstrates using the `write` driver in an `OnDisconnect` hook. It writes a message containing connection statistics (written bytes, duration, average speed) to the terminal when the SSH connection is closed.

```yaml
defaults:
  Hooks:
    OnDisconnect:
    - "write SSH connection to {{.Host.Name}} closed, {{ .Stats.WrittenBytes }} bytes written in {{ .Stats.ConnectionDuration }} ({{ .Stats.AverageSpeed}})"
# writes: SSH connection to localhost closed, 40 bytes written.
```

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