SUB(1)

💖 SUB(1) — like, the manual page, bestie 💖

okay so real talk, you found the man page for sub from the SUB(1) manual, and honestly? she's a baddie. let's get into it 🫶

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✨ NAME ✨

sub — subscribe to MQTT topics 🌸

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✨ SYNOPSIS ✨

sub [OPTIONS]

that's it. that's the whole vibe. no positional args, just options, and she eats every time 💅

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✨ DESCRIPTION ✨

sub connects to the MQTT broker you tell her about and subscribes to all the topics you specify. Every message that comes in on a topic gets printed to stdout, and it's prefixed with the topic the message arrived on, so you always know who's talking. main character behavior tbh 👑

and here's the cute part: every single option can be passed either as a command-line argument or written in a simple config file. your choice, your rules, no cap ✨

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✨ OPTIONS ✨

• -auto-reconnect — automatically reconnect when connection is lost. she comes back. she always comes back 🦋
• -broker URL — broker address (should be in the form of a URL)
• -ca-root FILE — path to a FILE containing CA certificates (optional)
• -cert-file FILE — authenticate with a certificate 🎀
• -clean — discard any pending messages from the broker (default true)
• -client-id STRING — unique identifier for this client (defaults to a semi-random string)
• -connect-retry — automatically retry initial connection to broker 🔁
• -connect-retry-interval DURATION — wait DURATION between initial connection attempts (default 30s)
• -config FILE — path to FILE containing configuration values (optional)
• -header KEY=VALUE — set an HTTP header (in KEY=VALUE form) (can be specified multiple times)
• -key-file FILE — authenticate with a private key 🔐
• -password STRING — authenticate with a password
• -qos INTEGER — quality of service for messages
• -tls-alpn STRING — ALPN value to include in the TLS handshake (can be specified multiple times)
• -topic STRING — topic to publish or subscribe to (can be specified multiple times) 💖
• -username STRING — authenticate with a username
• -verbose — increase output 🗣️
• -version — print version

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✨ CONFIGURATION ✨

Any option may be specified as a value in a configuration file instead of (or in addition to) a command-line option. like, you don't have to pick one, you can do both, it's giving polyamorous but for flags 💜

Values present on the command-line take precedent over values in the configration file. so the command line always wins, periodt 👑

Thus it is easy to create a base configration file that can be augmented easily at run time. build your little base, then spice it up on the fly. iconic.

The configuration file takes the form of a simple space-separated "option value" format (i.e. "broker tcp://test.mosquitto.org:1883").

ngl bestie, the original spells it "configration" twice — that's a typo in the man page itself, not a you problem. i'm keeping it exactly as written because facts are facts 🙈

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✨ EXAMPLES ✨

Connect to a broker anonymously and subscribe to two topics. ✨

sub -broker tcp://test.mosquitto.org:1883 -topic mqttcli/pubtest -topic mqttcli/pubtest1

Connect to a broker using username/password authentication and subscribe to a topic. 🔐

sub -broker tcp://test.mosquitto.org:1884 -username ro -password readonly -topic mqttcli/pubtest

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✨ AUTHOR ✨

Link Dupont <link@sub-pop.net>

• Author. 💖

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and that's the whole page, bestie!! this was SUB(1), dated 08/22/2026, and it's lowkey a masterpiece. go forth, subscribe to your topics, and slay 💅✨🎀🦋🌸💖🫶👑