# RouterOS SSH Line-Length Limit & Workarounds

**Verified on:** RouterOS 7.18.2 (CCR2004-16G-2S+)

## The Problem

RouterOS commands sent via `ssh <user>@<host> '<command>'` are truncated at ~170 characters. Anything longer produces `expected end of command (line 1 column NNN)`.

This bites when deploying SSH keys, writing scripts, or using `:convert from=base64` with long payloads.

## Workarounds

### A. `/file/add name= contents=` (best for Ed25519 keys, <170 chars)

```bash
ssh shonuff@192.168.88.1 '/file/add name="wisp-key.txt" contents="ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAA... wisp-backup"'
```

### B. `/user ssh-keys/add user= key=` (no intermediate file)

```bash
ssh shonuff@192.168.88.1 '/user ssh-keys/add user=shonuff key="ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAA... wisp-backup"'
```

### C. Global var + script split (>170 chars)

Create a global variable in one SSH call, then reference it in a script in another:

```bash
# Call 1: set global
ssh ... ':global mykey "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAA..."'

# Call 2: create script referencing the global
ssh ... '/system script add name=dk source=":local k \$mykey; :put \$k file=wisp-key.txt"'

# Call 3: run script
ssh ... '/system script run dk'
```

### D. Hex-encoded script (for RSA keys, >300 chars)

Convert each byte to `\XX` RouterOS hex escape, write as a script, run it:

```python
key = "ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQ..."
escaped = ''.join(f'\\{b:02X}' for b in key.encode())
script = f'/system script add name=dk source=":local k \\\"{escaped}\\\"; :put \\$k file=wisp-key.txt"'
```

Then on RouterOS:
```routeros
/system script run dk
/user ssh-keys import public-key-file=wisp-key.txt user=backup
```

## What Does NOT Work

| Method | Error | Why |
|--------|-------|-----|
| `:put "data" file=file.txt` | `expected end of command (line 1 column N)` | `file=` param not supported on v7 |
| SCP/SFTP | `exec request failed on channel 0` | No SCP subsystem on RouterOS |
| `:put [/file/get x contents]` | `no such item` if file missing | Fine if file exists |
| `:put ... file=` in RouterOS script | `syntax error` | Doesn't work in scripts either |
| `/tool/fetch` | `cannot open file: permission denied` | Requires `ftp` policy (not in read/write groups) |