# Correct way to use include and includeonly when writing a large document like a thesis

I am writing a large document with several chapters and I would like to work on each chapter separately. In my `main.tex` I include the chapters either like

`````` \include{chap1.tex}
\include{chap2.tex}
\include{chap3.tex}
``````

or

`````` \input{chap1.tex}
\input{chap2.tex}
\input{chap3.tex}
``````

I think `\include` is preferable if I want things to be referenced and cited correctly? but doing it the `\include` way `latex main.tex` I don't get any `dvi` output whereas with `\input` things compile fine to `dvi`. What's going wrong here?

I would then like to use `\includeonly` (or `\excludeonly` ) to work on individual sections of the document whilst maintaining the referencing etc.

thanks for any help.

-
I don't know if this is related to your problem, but I think you could remove the file extensions. Otherwise, perhaps a minimal working example (MWE) would help. – Corentin Dec 14 '12 at 11:23
I believe you should use `\include` at the level of a control file calling files for your chapters. On a related note, I found that `\include` is problematic inside a `\chapter`. So `\input` is also handy. – apexofservice Dec 14 '12 at 11:26
@Corentin good catch: I missed that in my answer. – David Carlisle Dec 14 '12 at 11:26
@fpghost You might want to look at When should I use \input vs. \include?, which looks quite similar to this question. – Joseph Wright Dec 14 '12 at 11:29
@Corentin that fixed it, thanks a lot – fpghost Dec 14 '12 at 11:35

Cross referencing and citation should work fine with `\input`. `input` is more or less invisible to the TeX processing, it just allows you to split up the file into smaller units for ease of editing.
If you do not use `\includeonly` then `\include{file}` is more or less the same as `\clearpage\input{file}\clearpage` so like `\input` but with forced page breaks. Since your chapter head probably forces a page break anyway this means that switching between `\input` and `\include` should not affect output.
If you use `\include` then you can use `\includeonly` to speed up processing by just typesetting specified chapters. Note however that it will use old `aux` files for the other chapters to get the numbering more or less correct. Thus you should occasionally (and initially) process the file without `\includeonly` so that all chapters are processed and usable `aux` files are generated for each chapter.
As noted by @Corentin in the comment, in the case of `\include` it is important that you use the file name without `.tex` at the end: `\include{file1}` not `\include{file1.tex}`.
Is it worth noting that `\include` is mainly for chapters? – Joseph Wright Dec 14 '12 at 11:28