CLI Reference¶

Cello applications are run directly with python app.py. Command-line arguments configure the server at startup and override any values passed to app.run() in code.

Usage¶

python app.py [OPTIONS]

Options¶

Flag	Type	Default	Description
`--host HOST`	`str`	`127.0.0.1`	IP address to bind to. Use `0.0.0.0` to accept connections on all interfaces.
`--port PORT`	`int`	`8000`	TCP port to listen on.
`--env ENV`	`str`	`development`	Environment name. Use `production` to disable debug mode and verbose logging.
`--workers N`	`int`	CPU count	Number of Tokio worker threads.
`--debug`	flag	Off in prod	Enable debug mode with verbose error pages.
`--reload`	flag	Off	Enable hot reload. Watches `.py` files and restarts on changes.
`--no-logs`	flag	Off	Disable request logging output.

Examples¶

Development Server¶

python app.py

Starts on 127.0.0.1:8000 with debug mode and logging enabled.

Production Server¶

python app.py --host 0.0.0.0 --port 8000 --env production --workers 8

Hot Reload (Development)¶

python app.py --reload

Watches all .py files in the current directory. When a change is detected, the server restarts automatically.

Custom Port¶

python app.py --port 3000

Disable Logging¶

python app.py --no-logs

Environment Variables¶

You can use environment variables instead of (or in addition to) command-line flags. Read them in your application code:

import os

app.run(
    host=os.environ.get("HOST", "0.0.0.0"),
    port=int(os.environ.get("PORT", "8000")),
    env=os.environ.get("CELLO_ENV", "development"),
    workers=int(os.environ.get("WORKERS", "4")),
)

Common Environment Variables¶

Variable	Purpose	Example
`CELLO_ENV`	Environment name	`production`
`HOST`	Bind address	`0.0.0.0`
`PORT`	Bind port	`8000`
`WORKERS`	Worker thread count	`8`
`JWT_SECRET`	JWT signing secret	Random string
`DATABASE_URL`	Database connection string	`postgresql://...`
`CELLO_RUN_MAIN`	Internal: set by the reloader	`true`

Precedence¶

When the same setting is specified in multiple places, the following order applies (highest priority first):

Command-line arguments (--port 3000)
Values passed to app.run() (port=3000)
Defaults

Programmatic Equivalent¶

Every CLI flag corresponds to a parameter on app.run():

app.run(
    host="0.0.0.0",       # --host
    port=8000,             # --port
    env="production",      # --env
    workers=8,             # --workers
    debug=False,           # --debug
    reload=False,          # --reload
    logs=False,            # --no-logs
)

Exit Codes¶

Code	Meaning
`0`	Clean shutdown (Ctrl+C)
`1`	Startup error (port in use, invalid config, etc.)