Run command

2 snippets across 2 stacks — Docker, Python

DKDocker

RUN — Execute Build Commands

syntax

RUN <command>
RUN ["executable", "arg1", "arg2"]

example

RUN apt-get update && apt-get install -y curl && rm -rf /var/lib/apt/lists/*
RUN pip install --no-cache-dir -r requirements.txt

Note Each RUN creates a new image layer. Combine related commands with && to reduce layers and image size. Always clean up package manager caches in the same RUN statement, or the cache ends up in a previous layer and is never actually removed.

PYPython

subprocess Module

PY · Common Standard Library

syntax

import subprocess
subprocess.run([cmd, args], capture_output=True)

example

import subprocess

result = subprocess.run(
    ["echo", "Hello from subprocess"],
    capture_output=True, text=True
)
print(result.stdout.strip())
print(f"Return code: {result.returncode}")

output

Hello from subprocess
Return code: 0

Note Always pass commands as a list, not a string. Use shell=True only when absolutely necessary — it introduces shell injection risks.