Working directory

WORKDIR — Set Working Directory

syntax

WORKDIR /path/to/dir

example

WORKDIR /app
COPY . .
RUN npm ci

Note All subsequent RUN, CMD, COPY, and ENTRYPOINT instructions use this directory. WORKDIR creates the directory if it does not exist. Avoid using RUN cd /app — it only affects that single RUN layer.

PYPython

os and os.path

PY · Common Standard Library

syntax

import os
os.path.join()
os.environ

example

import os

# Environment variables
db_host = os.environ.get("DB_HOST", "localhost")
print(f"DB: {db_host}")

# Path operations (prefer pathlib for new code)
print(os.path.expanduser("~"))
print(os.path.splitext("report.pdf"))
print(os.getcwd())

output

DB: localhost
/Users/username
('report', '.pdf')
/current/directory

Note Prefer pathlib.Path for path manipulation in new code. os.environ provides direct access to environment variables. Use os.getenv() for safe access with defaults.

DKDocker

PYPython