DBUS-MONITOR(1)

💅 dbus-monitor(1) — your new fave little debug probe

okay so first things first, bestie: this is a manual page from User Commands, and the whole thing is about dbus-monitor. that's the star of the show. let's get into it 🫶

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✨ NAME ✨

dbus-monitor — a debug probe that prints message bus messages. that's it. that's the job. it snoops (lovingly) on your bus and prints what it sees 💖

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🦋 SYNOPSIS 🦋

dbus-monitor [--system | --session | --address ADDRESS] [--profile |
             --monitor | --pcap | --binary] [watch expressions]

look at her. iconic bracket structure. no cap, this is literally the shape of the whole command 💅

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🌸 DESCRIPTION 🌸

okay so dbus-monitor is the command you use to monitor messages going through a D-Bus message bus. if you wanna know the big picture, like the whole lore, it's over at https://www.freedesktop.org/wiki/Software/dbus/ — go read it, it's giving foundational text 📚

so there are two well-known message buses, and you need to know both:

• the systemwide message bus — on many systems this is installed as the "messagebus" service
• the per-user-login-session message bus — this one gets started each time a user logs in

the --system and --session options point dbus-monitor at the system bus or the session bus respectively. and here's the default tea ☕ — if neither is specified, dbus-monitor monitors the session bus. she just picks for you, lowkey thoughtful.

dbus-monitor also has two different text output modes:

1. the 'classic'-style monitoring mode
2. profiling mode

the profiling format is a compact format — a single line per message, plus microsecond-resolution timing information ⏱️ (yes, microsecond. she's precise.) the --profile and --monitor options select the profiling and monitoring output format respectively.

and because one vibe isn't enough, there are also two binary output modes:

• the binary mode, selected by --binary, outputs the entire binary message stream (without the initial authentication handshake)
• the PCAP mode, selected by --pcap, adds a PCAP file header to the beginning of the output, and prepends a PCAP message header to each message — this produces a binary file that can be read by, for instance, Wireshark 🦈

and if no mode is specified at all? dbus-monitor uses the monitoring output format. default queen behavior 👑

so how do you actually get her to show you the messages you care about? you specify a set of watch expressions as you would expect to be passed to the dbus_bus_add_match function. that's the move 🎯

⚠️ real talk though: the message bus configuration may keep dbus-monitor from seeing all messages — especially if you run the monitor as a non-root user. so if something's missing, it might not be you, it's the config 🙈

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🎀 OPTIONS 🎀

• --system — monitor the system message bus 🖥️
• --session — monitor the session message bus. and psst, this is the default ✨
• --address ADDRESS — monitor an arbitrary message bus given at ADDRESS 🌈
• --profile — use the profiling output format ⏱️
• --monitor — use the monitoring output format. also the default, she's consistent 💖

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⭐ EXAMPLE ⭐

here's an example of using dbus-monitor to watch for the gnome typing monitor to say things 👀

dbus-monitor "type='signal',sender='org.gnome.TypingMonitor',interface='org.gnome.TypingMonitor'"

literally just copy that, it ate 🔥

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💜 AUTHOR 💜

dbus-monitor was written by Philip Blundell. the profiling output mode was added by Olli Salli. legends, both of them 👑🫶

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💀 BUGS 💀

please send bug reports to the D-Bus mailing list or bug tracker — the link is https://www.freedesktop.org/wiki/Software/dbus/ — they wanna hear from you, fr fr 🐛

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and that's the whole page bestie!! mwah 💋 this was D-Bus 1.16.2, dated 03/03/2025 — so if you're reading this way later, maybe go check if there's a glow-up version 🌟 iykyk