"apt-mark showmanual" will show you all packages that you have manually installed
"apt-mark showauto" will show you all packages that are automatically installed
"apt-mark showinstall" will show you all the packages that are installed
How is this useful? It tells you what packages are installed in your system.
So you can go "apt-mark showinstall | grep somelibrary" to see if you have a particular library installed that's a dependency.
Cisco Catalyst C9300-24UX-A 24 Port 10G/mGig UPOE Network Switch, no module
$279.97
Cisco Catalyst C9300-24UX-A 24 Port 10G/mGig Copper UPOE Network Switch
$475.00
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$174.00
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$110.00
🔥🔥🔥 CISCO SFP-10G-SR V03 10-2415-03 850nm 10GBASE-SR SFP+ Multi Module 🔥🔥🔥
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$297.00
Cisco C3850-NM-2-10G 2 Port Network Exp.Module for 3850
$30.99
GENUINE Cisco SFP-10G-SR V03 SFP+ GBIC Transceiver Module 10-2415-03
$6.80
Cisco 3560CG Series 8 Port POE Network Switch WS-C3560CG-8PC-S
$80.00
Cisco 2900 Series CISCO2901/K9 v06 Integrated Services Router
$39.99