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.

  • 1
    Let me make a guess: It's an error message about an already defined command?
    – user31729
    May 24, 2015 at 18:47
  • @christian That's right. My question was answered, but I am trying to find out how to look up the error for myself
    – Dov
    May 24, 2015 at 18:49
  • 1
    I think it's the original manual made by Leslie Lamport himself: LaTeX: A document preparation system
    – user31729
    May 24, 2015 at 18:56
  • Which also happens to be fewer than 192 pages, if memory serves :-) May 24, 2015 at 19:01
  • 3
    It's on my shelf, by The TeXbook and The LaTeX Companion. :-) May 25, 2015 at 14:44

3 Answers 3


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.)

  • 1
    IMO In page 43 line 219 of source2e V1.2n, 29/09/2014 the LaTeX error message see p.192 of the manual might be changed to See the LaTeX manual or LaTeX Companion for explanation to avoid any confusion for user or even See p.192 of Leslie Lamport LaTeX manual for explanation to be more precise. May 25, 2015 at 4:40
  • Just a light comment. I recently read some articles referenced by Babara Beeton where it is implied that LaTeX was around already in 1982. May 25, 2015 at 7:54
  • 1
    @MartinArgerami The LaTeX2.09 file ltplain.tex has comment Created 29 October 1985 from plain version 1.5CM, which gives us an approximate date. Real take-up of LaTeX I believe started in the late 1980s.
    – Joseph Wright
    May 25, 2015 at 8:05
  • 1
    @JosephWright: take a look at this article, published in Sept 1983. On page 95 you can read "LaTeX is already available"; it is also mentioned in others letters in the article. It is hard to claim that it was "written in the mid 80s". May 25, 2015 at 13:52
  • 1
    @FriendlyGhost The text is still copyright (like many texts). I'm afraid if I want to properly read something I want it in printed form, so free or not dead trees will be involved.
    – Joseph Wright
    May 27, 2015 at 11:08

The manual which the error message refers to is

Leslie Lamport, LaTeX: A Document Preparation System (second edition)

published by Addison-Wesley. The publisher's page is at



This does only partially answer the question, but just notes where the error messages comes from: latex.ltx

   Command \@backslashchar\reserved@a\space
   already defined.\MessageBreak
   Or name \@backslashchar\@qend... illegal,
   see p.192 of the manual}\@eha}

The page number is coded into the error message, but does not specify which manual is meant actually.

Under texlive/doc/latex/base/manual.pdf we just find errata to the 2nd edition, which does not give any clue.

Looking into source2e.pdf, we find nothing really connected to this.

After using google, I found that it is fact the Book by

Leslie Lamport: LaTeX A Document preparation system.

(I found a link where a scanned copy of that book is available)

For reasons of copyright issues, I won't provide the link here.

Basic summary of the relevant page 192:

It's about the commands

  • \newcommand
  • \renewcommand
  • \providecommand,

effectively stating, that a command name must not be defined before to be used with \newcommand etc.

So if the error message occurs, the command has been defined before already.

  • 2
    Of course it does not give any glue :) hehehe
    – Manuel
    May 24, 2015 at 19:10
  • @Manuel: Just a joke ;-) (No, a typo)
    – user31729
    May 24, 2015 at 19:12

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