shellsafe

Safe shell commands via Python 3.14 template strings. Injection-proof by construction.

from shellsafe import run

message = get_user_input()          # "fix; rm -rf ~"
run(t"git commit -m {message}")
# argv: ["git", "commit", "-m", "fix; rm -rf ~"]
# one command; the scary text is just an argument

Why

The dominant pattern in scripts and automation is still this:

subprocess.run(f"git commit -m {message}", shell=True)   # injection waiting to happen

Python 3.14 template strings (t"...") separate static text from interpolated values. shellsafe turns that structure into argv lists where interpolated values are always data, never commands. When you genuinely need pipes, shell mode quotes every value with POSIX rules first.

Install

pip install shellsafe

Requires Python 3.14+ (template strings).

Usage

Run a command. Interpolated values are always single arguments:

from shellsafe import run

run(t"mkdir {path}")
run(t"docker build -t {tag} .", check=True, timeout=300)

Capture output as text:

from shellsafe import capture

res = capture(t"grep {pattern} {file}")
print(res.stdout, res.returncode)

Pipes and redirections on POSIX (values are quoted with shlex.quote first):

from shellsafe import shx

shx(t"cat {file} | wc -l")

Inspect exactly what will execute:

from shellsafe import plan  # lower-level: render without running

print(plan(t"git commit -m {message}"))
# argv: ["git","commit","-m","fix; rm -rf ~"]

What it refuses

Case Behavior
Interpolation as the executable error: the command comes from static text only
Shell route on Windows error: cmd.exe quoting cannot be made injection-safe; use argv mode
RAW misuse error: one argument, verbatim, nesting refused

RAW("...") / RAW(["a", "b"]) is the single explicit trust boundary for pre-quoted content. Every use site is greppable.

Limits

  • Windows: interpolated shell routes are refused rather than approximated; argv-mode commands work fully.
  • Bytes interpolations are rejected: decode explicitly first.
  • Runtime behavior after import is your test suite's job, same trust model as calling subprocess yourself.

Contributing

Issues and PRs welcome. Security reports go privately to the maintainer, never through public issues.

Requirements

  • CPython >= 3.14 (uses template strings from PEP 750)
  • Linux, macOS, Windows (Windows supports argv mode; POSIX-only shell mode)

License

MIT

Project links

Data verified by PyPI on Aug 24, 2026
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Key dates

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  • Released:
Newer release available (0.3.2)

1 maintainer

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Avatar for rahulXs from gravatar.com rahulXs

Credits

Author: Rahul Sharma

GitHub Statistics

Data verified by PyPI on Aug 24, 2026
The GitHub source repository was provided by the project maintainers and verified by PyPI at the time of upload. Stars, forks, and open issues/PRs are derived from that repository and have not been independently verified.

License expression

MIT
View SPDX License List

Requires

Python >=3.14

Tags

automation command-injection injection pep750 security shell subprocess t-strings template-strings

Classifiers

Report project as malware

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