Tramp

lem-tramp

Lem-tramp is transparent and remote file editing for Lem.

It works like Emacs’ TRAMP — type a remote path into C-x C-f and edit the file as if it were local.

Supported Methods

Method	Syntax	Description
`ssh`	`/ssh:user@host:/remote/path`	Edit files on a remote host via SSH
`sudo`	`/sudo::/local/path`	Edit local files with root privileges via sudo

Current limitations

Lem-tramp does not support:

accessing directories. Only files.
hiding passwords when connecting with /sudo.
Windows. This is Unix only.

Usage

Open a file with C-x C-f using the TRAMP path syntax:

C-x C-f /ssh:root@example.com:/etc/nginx/nginx.conf
C-x C-f /sudo::/etc/hostname

The remote file is loaded into a buffer. Edit normally, then save with C-x C-s.

For example:

C-x C-f /ssh:debian@1.2.3.4:/home/debian/test.txt

Authentication

SSH (`/ssh:`)

Key-based auth (recommended) — no prompt, works automatically if you have SSH keys set up and your key is in the remote host’s authorized_keys.

Password auth — requires the sshpass utility:

# Arch
sudo pacman -S sshpass
# Debian/Ubuntu
sudo apt install sshpass

When key auth is unavailable, a password prompt appears in the minibuffer. The password is cached for the session; subsequent file operations on the same host reuse it without re-prompting.

Sudo (`/sudo::`)

A password prompt appears if your sudo timestamp has expired (typically 5-15 minutes since your last sudo invocation in a terminal). If you have passwordless sudo configured (NOPASSWD in sudoers), no prompt is shown.

How It Works

lem-tramp hooks into Lem’s virtual filesystem layer:

Reading — runs cat /remote/path via SSH (or sudo), loads the output directly into an in-memory buffer.
Writing — pipes the buffer content through cat > /remote/path.
Directory listing — uses ls -1a for completion and directory-mode.
Metadata — uses stat -c '%s %Y' for file size and modification time.

No temporary files are created on either the local or remote side.

Dependencies

sshpass — only needed for SSH password authentication
flexi-streams, str, babel, ppcre — Common Lisp libraries

Terminal Integration

When a buffer is visiting a TRAMP path, M-x terminal opens a terminal in the remote file’s directory on the appropriate host:

Buffer path	Terminal command
`/sudo::/etc/nginx/`	`sudo bash -c "cd /etc/nginx; exec bash"`
`/sudo:root::/var/log/`	`sudo -u root bash -c "cd /var/log; exec bash"`
`/ssh:user@host:/var/log/`	`ssh -t user@host "cd /var/log; exec ${SHELL:-/bin/sh}"`

Authentication happens interactively inside the terminal PTY — sudo and ssh prompt for passwords naturally, without involving TRAMP’s password management. Key-based SSH auth works transparently.

Performance

SSH connections use ControlMaster multiplexing — the first command establishes the TCP connection, and all subsequent commands reuse it. A 5-second filesystem cache eliminates redundant test -d / test -f / stat calls when Lem probes the same path multiple times during a single file-open operation.