Command files

--commands-root DIR lets a simulated device answer any CLI command with the contents of a file you provide. Use it for output the generator does not produce, such as LLDP/CDP neighbour tables, interface listings, or a vendor-specific show version, for example to demo or test topology discovery across vendors.

The flag is off by default. With it unset, every driver behaves exactly as before, byte for byte.

./bin/rcfg-sim \
  --manifest manifest.csv \
  --listen-ip 127.0.0.1 --port-start 12700 --port-count 3 \
  --commands-root /path/to/commands

Folder layout

There is one folder per device, named exactly after the manifest hostname, and one file per command:

commands/
  core-01/
    show_lldp_neighbors_detail.txt
    show_interfaces.txt
    show_version.txt
  dist-01/
    show_lldp_neighbors.txt
    show_interfaces.txt

Slug rule

The file name is <slug>.txt. The slug is the typed command:

1. trimmed, with runs of whitespace collapsed to one space
2. lowercased
3. with a trailing | no-more removed
4. with spaces replaced by _

Typed	File
show lldp neighbors detail	show_lldp_neighbors_detail.txt
Show LLDP Neighbors	show_lldp_neighbors.txt
show cdp neighbors detail | no-more	show_cdp_neighbors_detail.txt
show configuration | display set	show_configuration_|_display_set.txt

Because the slug is always lowercase, file names must be lowercase too. A command containing / or \ (RouterOS-style /interface print, say) is never looked up, so a client cannot reach outside the device’s folder.

How a command is answered

• The file is checked before the driver’s built-in commands, so a file can override one, for example to give an Arista device a real EOS show version.
• A hit sends the file with CRLF line endings, whatever the file uses, ending in CRLF, and then the usual prompt. It is subject to the normal response delay and slow_response fault.
• A miss falls through to the built-in behaviour unchanged, including the driver’s usual “invalid input” error.
• A missing root, or a device with no folder, simply means no files for that device. It is not an error.

Command files apply to the cisco_ios and junos drivers. TL1 drivers do not look up files.

Caching

A device’s folder is listed once, on that device’s first command, and each file is read on its first hit. Both are kept for the life of the process.

Restart after changing files

Files added, removed or edited after a device has been used are not seen until the instance restarts. The same goes for a device folder created after startup.

Nothing a client types can grow the cache, which is bounded by the files on disk. A miss costs a map lookup, never a disk read.

Metrics

Every file-served command is recorded under one label value, rcfgsim_command_duration_seconds{command="file"}, however many commands are file-backed. The series is pre-registered only when --commands-root is set. See the metrics reference.

Example

The repo ships the mesh-campus scenario, a three-vendor campus built entirely on command files.