SSHScript

SSHScript is a Python automation library for running commands locally and over SSH through one Session API. It also provides optional dollar syntax for compact .spy automation files.

SSHScript aims to help engineers and AI agents execute, understand, and hand off automation reliably: identify the execution host, retain each command's output and status, distinguish failure from timeout, and make cleanup and unknown termination explicit. A successful command exit is evidence about that command; verify the deployment or other application outcome separately.

Current release: 4.0.2 (Production/Stable) · Python: 3.11 or newer · Tested: Python 3.11–3.14 on Linux and macOS

Documentation · PyPI · Changelog · Security · Support

Version 4.0.2 maintains the 4.0 execution contract introduced in 4.0.1. This patch aligns the published documentation and installation links. Upgrade 3.1.5 automation using the migration guide and application regressions. See version policy and migration before upgrading automation.

Recommended API

Start with the canonical API guide: version-labelled examples, recommended argv/check/result patterns, lifetime rules, and compatibility forms. Its executable examples run in CI. The same guide is available in the website documentation.

The 4.0 source also ships py.typed and public .pyi declarations for Session, results, jobs, console calls and package entry points. Legacy live buffers and backend-specific keyword options retain Any; this is targeted public typing, not a claim that every internal module is fully annotated.

In 4.0 source, su() and sudo() accept enter_timeout=10 and return a console only after authenticated startup and a target-shell UID/PID handshake. Passwords are sent at most once; an unconfirmed recovery makes the channel unusable. Custom nested command= strings now require a bootstrap placeholder. See authenticated console usage and migration and the cross-system test guide.

Why SSHScript?

• Use the same interface for local subprocesses and remote SSH commands.
• Traverse nested SSH connections without rebuilding connection logic.
• Keep ordinary Python functions, packages, exceptions, data processing, and threading around your automation.
• Scope connections, privilege changes, persistent shells, and interactive programs with context managers.
• Read stdout, stderr, and exit status directly after each command.
• Add concise dollar syntax only where command-shaped notation improves a script.

Install

SSHScript requires Python 3.11 or newer. Installing in a virtual environment is recommended:

python3 -m venv .venv
. .venv/bin/activate
python3 -m pip install --upgrade pip
python3 -m pip install sshscript
sshscript --version

On Python versions below 3.11, SSHScript stops before loading its features. The CLI reports the detected version and interpreter path without a traceback; importing the Python API raises ImportError with the same diagnostic.

For a production deployment that requires repeatable dependency resolution, pin SSHScript and all transitive dependencies in your application's lock file. To install this release explicitly:

python3 -m pip install "sshscript==4.0.2"

Use python3 -m pip install --upgrade sshscript to upgrade. The optional sshscript --check-updates command queries PyPI and prints an upgrade command; it never installs an update by itself.

60-second local quickstart

This example runs on 4.0.2 and retains compatibility with the 3.1.5 command API. The metadata below records that older compatibility baseline.

import sys

from contextlib import closing
from sshscript import Session

command = [
    sys.executable,
    "-c",
    "print('sshscript is ready')",
]

with closing(Session()) as local:
    stdout, stderr, exitcode = local.exec_command(
        command,
        shell=False,
        check=True,
    )
    print(str(stdout).strip())
    print(f"exit code: {exitcode}")

Expected output:

sshscript is ready
exit code: 0

closing(Session()) closes the local Session when the block ends. Plain with Session() only activates a reusable local Session; it does not close it. closing calls close() without inspecting its bool return. Inspect close_errors or use close(strict=True) when cleanup failure must be reported, while preserving an exception already raised by the block. See the canonical lifetime rules.

exec_command() accepts one nonempty command string or a nonempty list/tuple of string arguments. An argument sequence means one command, not a batch. Sequences execute directly on the local host and are quoted for a POSIX login shell over SSH; shell operators inside them are literal arguments. They accept only shell=None or shell=False, without shell_executable. Use a string with shell=True when you intentionally need shell operators.

with closing(Session()) as local:
    result = local.exec_command(
        [sys.executable, "-c", "import sys; print(sys.argv[1])", "a; b"],
        check=True,
        timeout=30,
    )
    print(result.stdout, result.exitcode, result.duration)
    stdout, stderr, exitcode = result  # three-value unpacking

Each call returns an immutable CommandResult containing text stdout and stderr, exitcode, host, duration, and command. host snapshots session.host (None locally); it does not execute hostname. duration is elapsed monotonic seconds for command execution and output collection, including communication and worker cleanup but excluding connection setup. command is the normalized string or an immutable tuple of arguments. session.last_result references the most recently completed command; saved results remain valid after later commands or session closure. Validation failures leave it alone; starting a command clears it until completion.

Both local and remote commands accept check=True to raise subprocess.CalledProcessError for a nonzero status after preserving the result. The exception has text stdout/stderr, the normalized cmd, and a result attribute. With the default check=False, a nonzero status is result data. Connection errors and timeouts propagate unchanged.

Compatibility: the returned object is no longer a tuple of live output buffers. Unpack exactly three values: stdout, stderr, exitcode. Indexing and slicing use that same three-value order; old two-value unpacking must change. Use session.stdout/session.stderr for the existing buffer interface. 4.0 persistent shell commands also return CommandResult snapshots. Interactive console APIs retain their existing buffer and prompt semantics. For completed commands inside or outside a shell, save the result and read its fields. For continuous output such as tcpdump, choose a bounded capture, a managed streaming job, or an interactive enter() scope; see the execution and long-command guide.

Stdin data and interactive replies (4.0)

exec_command(input=data) and start(input=data) preserve stdin exactly on local and SSH backends: strings use UTF-8, bytes stay bytes, and no newline is added. To supply a line, write input=answer + "\n". This fixes the legacy SSH string-input behavior; published 3.1.5 still appends a newline on that path. Stdin closes after the data is sent, including for empty input. input=None supplies no data and retains the backend's existing stdin policy; legacy local execution may inherit stdin. Use empty input when explicit EOF is needed.

In a persistent shell, shell(command) executes a command and waits for its result. For a program's questions, enter it with shell.enter(...), then use program.input(answer) to append one Enter and wait for readiness, exit, or silence; use program.send(text) for exact text. Existing newlines are retained: input("answer\n") sends two newlines. Interactive readiness is not command success. Some password prompts read a terminal, so supplying stdin is not a substitute for a PTY conversation. See the input contract and migration.

Session settings (4.0)

session.set(check=True, verbose=False, log_level="DEBUG")
print(session.get())          # Independent copy of effective settings.
print(session.get("check"))   # True
session.verbose = True       # Same validation as set(verbose=True).
session(["false"], check=False)  # Explicit per-command override.

In .spy, use $.set(...) and $.get(...). Settings are check, verbose, verbose_stderr, log_level (logging integer or level name), and policy (a Paramiko MissingHostKeyPolicy instance or subclass, or None). New root Sessions snapshot package/application defaults; CLI -v, --stderr, and --debug override defaults only in that execution context. Child Sessions snapshot their parent's current settings. Existing Sessions are independent. set() validates every key/value before applying changes; unknown keys fail. Properties and set/get use the same storage. Command options override settings; running jobs retain their startup policy. Shell commands inherit check and can override it per call; interactive prompt input is not an exit-status check. Session logging never changes the shared logger level; application handler filters/levels still apply. Verbose explicitly prints command output and may expose sensitive output. No console logging handler is installed by Session.

Set session.set(policy=paramiko.AutoAddPolicy()) or assign session.policy to choose the missing-host-key policy for future connections (import paramiko first). The default is None, retaining Paramiko's RejectPolicy. An explicit connect(policy=...) wins for that connection; connect(policy=None) uses default rejection. Children inherit the Session setting, even when a connection uses an override. Settings dictionaries are copied, but policy objects are shared; custom policies should support reuse. Existing connections keep their original policy.

Foreground jobs in persistent consoles (4.0)

console.start(command) and $.start(command) inside shell/sudo/su return a CommandJob in the current Bash console, retaining cwd/environment/identity. Ordinary calls still return completed CommandResult snapshots. Each console permits one foreground job; use its stream/wait/stop methods before issuing another command. Console jobs default to a 60-second total deadline. PTY stop requests Ctrl-C and verifies recovery to the original UID/PID; an unresolved recovery disables the channel. Pipe consoles cannot safely cancel a running job. See console foreground jobs for executable examples, quoting, thread ownership and failure handling.

Managed deadlines and long-running commands (4.0)

The source checkout adds a total deadline shared by local and SSH commands:

result = session.exec_command(["uname", "-s"], command_timeout=30, check=True)

This opt-in path returns JobResult (a CommandResult subclass), retains at most 1 MiB of output per stream by default, and raises CommandTimeoutError with partial output on expiry. command_timeout=None selects managed execution without a deadline. Legacy exec_command(timeout=...) keeps its existing backend-specific behavior; do not combine the two parameters.

Use Session.start() for a command that runs until its user stops it:

from contextlib import closing
from sshscript import Session

with closing(Session()) as local:
    with local.start(["tcpdump", "-l", "-n", "-i", "eth0"],
                     timeout=None, stop_timeout=5, check=True) as capture:
        try:
            for chunk in capture.iter_stdout():
                print(chunk, end="", flush=True)
        except KeyboardInterrupt:
            pass
        finally:
            result = capture.stop()
        print("\nTermination:", result.termination_status)

Choose an interface on your host and run under an account authorized to capture packets. start(timeout=...) always means a total command budget; None means no deadline. Local stop sends SIGINT to the owned process group, then escalates after stop_timeout. Remote stop can attempt Ctrl-C with get_pty=True, but closing an SSH channel alone does not prove termination: inspect termination_status. A job context and Session.close() clean up active jobs. Streaming yields chunks, with bounded buffering and explicit overflow errors.

See Timeouts, cancellation, tcpdump, and cleanup for the timing contract, remote example, output limits, and migration details. These new APIs are not present in the published 3.1.5 package.

Session lifetime (4.0 close safeguards)

Use console and remote Session contexts to manage their scoped resources. A local with Session() activates a reusable Session; leaving that block does not close it. Use contextlib.closing(Session()) when the outer scope should also release the local Session, as shown in the canonical API guide.

To permanently stop using a Session, leave its console contexts first, then call close() (or close(strict=True) to raise on cleanup failure). Closing a Session with an active shell/su/sudo/enter context on itself or a descendant raises RuntimeError before any cleanup or state change, even with strict=False. Return from a function or propagate an exception to leave a console early. Closing a child Session leaves its parent usable.

After close, new work is rejected; repeated close calls retain the cleanup outcome. closed=True means the Session is disabled, while the close return value and close_errors report whether all cleanup succeeded.

First secure SSH connection

SSHScript uses Paramiko and verifies system host keys by default. Before the first connection, place the server key in the account's standard known_hosts file and verify its fingerprint through an independent trusted channel. Prefer an SSH agent, managed private key, or secret manager over a password embedded in source code.

from contextlib import closing
from sshscript import Session

with closing(Session()) as local:
    with local.connect(
        "ops@example.net",
        timeout=30,
        banner_timeout=30,
        auth_timeout=30,
    ) as remote:
        result = remote.exec_command(
            ["uname", "-s"],
            check=True,
            timeout=30,
        )
        print(result.stdout.strip())

Unknown and changed host keys are rejected unless the caller explicitly supplies a different Paramiko policy. Do not use automatic key acceptance in a production workflow unless a separate trusted bootstrap process has already verified the key. See the SSHScript documentation for nested connections, timeouts, file transfer, sudo, su, and interactive programs.

Reusing SSH configuration

Connections from a local session read ~/.ssh/config if it exists. Supported settings are Host patterns, HostName, User, Port, IdentityFile, ProxyCommand, and ProxyJump. Explicit API arguments override config, then built-in defaults apply. port=None means unspecified; an explicit port=22 overrides a configured port. Explicit pkey, pkey_path, or key_filename overrides configured identity files. Host-key verification remains enabled.

from contextlib import closing
from sshscript import Session

# Inspect effective settings without connecting or starting a proxy process.
settings = Session.resolve_connection("production", port=2222)

with closing(Session()) as local:
    with local.connect("production") as remote:
        result = remote(["uname", "-s"], check=True)

Pass ssh_config=False to disable config lookup, or ssh_config="/path/config" to require a particular file. Nested connections do not read local config unless an explicit file is supplied; proxy options remain unsupported on nested sessions. session.host and result.host use the resolved HostName. resolve_connection() returns effective Paramiko keyword arguments plus proxyCommand, when applicable; it performs no network operations.

Config tokens %h, %n, %p, %r, %u, %d, and %% are expanded after explicit overrides for identity paths and configured proxy commands. Other tokens fail clearly. Explicit proxyCommand strings retain their historical verbatim behavior. Explicit proxyCommand=None disables configured proxies. You can also supply proxyJump="user@bastion:2222" or a comma-separated chain. When both configured proxy types are active, select one explicitly or remove the conflict; SSHScript does not implement OpenSSH's first-proxy-wins rule.

ProxyJump uses the local ssh executable to forward to the target, with batch authentication and strict host-key checks on jump hosts. It requires known host keys and noninteractive authentication for those hops. The target connection remains managed and verified by Paramiko. A custom config file is also passed to ssh; otherwise its user config is used when present.

This is a subset of OpenSSH configuration. Match, Include, and hostname canonicalization are rejected before lookup; other unapplied options produce a warning. In particular, alternate known-hosts files and identity-agent settings are not imported. Treat config and proxy commands as trusted local inputs; connecting may execute configured proxy programs.

Optional dollar syntax

The regular Python Session API and optional .spy syntax share execution semantics. Save this as health.spy (Dollar syntax is not ordinary Python):

result = $(["printf", "%s", "ready"], check=True)
print(result.stdout)

Run it with sshscript health.spy; expected output is ready. This is a single-command example using the published 3.1.5 API, not the library test gate.

Check one file without executing its Python, imports, or commands:

sshscript --check health.spy

The exit status is 0 for valid syntax, 1 for a syntax/read failure, and 2 for invalid CLI usage. Syntax diagnostics show the original file, line, source, and caret. sshscript.check_file(path) provides the same compile-only check and raises source-located SyntaxError or filesystem errors. It validates Python/dollar syntax, not shell commands, imported modules, or remote hosts. --script remains available to inspect generated Python without execution. For compatibility, --check without a file still checks PyPI for updates; use --check-updates explicitly for that purpose.

In version 3, a single $ supports direct commands and shell features such as pipelines and redirection. The old $$ form is retained for compatibility but is deprecated. New applications should start with the regular Python module API and adopt dollar syntax only when its notation is useful.

The CLI and run_file() execute one file. Directories, globs, and multiple paths are intentionally unsupported. Importing SSHScript does not globally enable imports of .spy modules; use the temporary sshscript.spy_imports() context manager when a regular Python program needs that behavior.

Security model

SSHScript executes commands and Python code; it is not a sandbox. Treat every .spy file, Python module, command string, remote host, and command output as a trust boundary. In particular:

• never run unreviewed automation with production credentials;
• avoid shell interpolation of external data;
• keep credentials, private keys, inventories, and captured production output out of source control;
• verify host keys independently and retain timeouts around network operations;
• validate site-specific PAM, sudoers, shell, and network policy in a disposable environment before rollout.

See the security policy for the complete reporting and security model, and the stable exception contract for runtime behavior.

Release confidence and provenance

The 3.1 release line uses the following public controls:

• CI on Linux and macOS with Python 3.11, 3.12, 3.13, and 3.14;
• normal and optimized-mode tests, syntax smoke tests, compile checks, and a runtime-assertion gate;
• disposable loopback OpenSSH integration tests for host keys, SFTP, PTY, sudo/su, and timeout behavior;
• CodeQL and Dependabot;
• PyPI Trusted Publishing with short-lived OIDC credentials;
• GitHub build-provenance attestations and a SHA-256 verified.json manifest attached to the GitHub Release.

Download distributions from PyPI or the GitHub Release, not from unverified mirrors. These controls establish tested behavior, artifact integrity, and release provenance; they are not a substitute for reviewing the automation you run or for validating your production environment.

Compatibility and support

See the support policy for scope, support channels, and the information needed in a useful bug report.

Development and verification

The credential-free library gate is python3 tools/run_checks.py. A source checkout keeps modules and unittest/ at the root; a release checkout uses src/sshscript/. The tools detect both layouts. From either repository root:

python3 -m pip install 'paramiko>=2.11,<5' 'packaging>=21' build twine
python3 tools/run_checks.py
python3 tools/check_release.py --output /tmp/sshscript-candidate-UNIQUE

The output directory must not already exist. run_checks.py locates the test suite under unittest/ or src/sshscript/unittest/ automatically. See the contributing guide before proposing a change and the release guide for maintainer-only release steps.

Project policies

• Changelog
• Support policy
• Security policy
• Stable exception contract
• Contributing guide
• Code of Conduct

License

SSHScript is released under the MIT License.