less gives a bunch of files opened

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It says /usr/bin/less: 1: [:missing]
At least one file or directory argument required.

I’m a linux beginner, i started to learn the basic and mess around with the system files for few days. Perhaps i broke something, and when i wanted to see a file using less, it gives me a bunch of man pages, and it didn’t stop.

How can i figure out where or what is wrong and fix it?

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Author: Reynald Lamury