Helpful members of the community just solved my problem with \newcommand:
What's wrong with my newcommand?
But in trying to solve it, I got an error message referring to p. 192 of "the manual". I would like to look up the error myself.
I am compiling under Windows using the command:
latexmk -pdf file.tex
I cannot find a link to a manual on latex-project.org. There are links to books which are published commercially, but surely that is not what the error messages refer to?
The not-so-short guide has fewer than 192 pages, so that's obviously not it.
Best Answer
The 'manual' for LaTeX is LaTeX: A Document Preparation System by Leslie Lamport. This is as you observe a commercial book and one is therefore expected to visit a bookshop or library to obtain a copy. As you might also note, much of the same information as in Lamport's book is available in one or another free form (and other commercial offerings).
To understand why the manual is a book, it's worth remembering that LaTeX was first written in the 1980s based on software developed in the late 1970s to early 1980s. It's also worth remembering that (La)TeX is a typesetting system. At the time it was written, there were no electronic formats for reading documents on-screen, and printing a long document meant getting it done using a very expensive machine. As such, most software came with a proper manual. LaTeX is free, so the only way to pay for the cost of such a book was to charge for the book. (The same remains true for TeX itself, where the only way to get Knuth's manual is to buy The TeXbook.)
The LaTeX kernel is very stable, and so that message probably dates to code written by Lamport, with perhaps an update to the page number for LaTeX2e (1994). (Page 192 of Lamport's book does indeed describe the formal syntax for
\newcommand.) Writing a new official manual would be a lot of work. (I'd also say the assumption that to be proficient with a complex system such as LaTeX you should read some read documentation remains sensible.)