Python's subprocess.run for Mojo: run a program, capture stdout and stderr, feed it input, with timeout, cwd, env and check. Large outputs on both pipes are drained together, so nothing deadlocks. 164 lines of code (mojo-loc) on top of mojo-posix (vendored in src/posix).
from subprocess import run
var r = run(["git", "rev-parse", "HEAD"], timeout=5.0)
if r.returncode == 0:
print(r.text()) # stdout as text; r.stdout / r.stderr are bytes
var cat = run(["sort"], input="b\na\n".as_bytes())Checked against Python subprocess: exit codes and signal deaths (-9, -15, -2), a 3 MB + 3 MB flood on stdout and stderr at once, a 5 MB stdin echo, a child that exits without reading its input, head closing early, cwd and env, argv with spaces, empty strings and Unicode, empty input (EOF), stdout and stderr byte-identical; timeout, missing program, empty argv, check and check_output raise where Python raises, with the same return codes (the error texts are this library's own, see docs/api.md). scripts/check.sh, each scenario twice. 6 of 6 mutants caught. Builds and passes on Mojo 1.2.0 and the 1.3 nightly.
Speed (7800X3D, load average about 29 at the time): run(["true"]) 418 µs and 0.60 GB/s through cat; Python 543 to 1,155 µs and 0.35 to 0.47 GB/s across runs.
Requires Linux 5.3 or newer for the pidfd (older kernels fall back to polling waitpid every millisecond) and glibc 2.29 or newer (posix_spawn_file_actions_addchdir_np). The program is looked up on this process's PATH, also when env sets another PATH (Python uses the PATH from env); pass an absolute path in that case.
- API: docs/api.md · design: docs/design.md · agent skill: skills/mojo-subprocess/SKILL.md
- License: Apache-2.0