While we're discussing man pages, a common annoyance is that the man page on a command is, at times, too large. Take the ps(1) utility as an example. It has a large man page as, of course, it has a huge number of option switches. Wouldn't it be nice, though, to have a simplified and summarized "common usage" page? This is precisely what the tldr pages project aims to do.
In their own words, they provide "simplified and community-driven man pages." So, once installed, tldr ps provides a neat brief summary on the most commonly used ps command option switches to do something useful:
It's indeed worth checking out. If you're interested in knowing more, visit https://tldr.sh/.
Earlier, recall that we said that userspace system calls fall under section 2 of the man pages, library subroutines under section 3, and kernel APIs under section 9. Given this, then, in this book, why don't we specify the, say, printk kernel function (or API) as printk(9) – as man man shows us that section 9 of the manual is Kernel routines? Well, it's fiction, really (at least on today's Linux): no man pages actually exist for kernel APIs! So, how do you get documentation on the kernel APIs and so on? That's just what we will briefly delve into in the following section.