I understand that "the convention is to use \RequirePackage in a package or
class and \usepackage in a document", but apart from that, is there any practical difference between the two commands?
(I am thinking for example that it could be the case that \RequirePackage is a "stronger" command and you wouldn't run into problems with hyperref not being at the end)
Sorry but there is a difference, you can write :
\RequirePackage{atbegshi}
\documentclass ....
and not
\usepackage{atbegshi}
\documentclass ...
myclass.cls, and \documentclass{myclass} it on main.tex. As per comment and answers around here I cannot usepackage{anypackage} before \documentclass{myclass} on main.tex. But looks like I still can usepackage{anypackage} on myclass.cls, which I wasn't expecting. Does this makes sense?
– KcFnMi
Apr 3 '19 at 17:32
The only difference is that \usepackage cannot be used before \documentclass. Otherwise there is no functional difference. The LaTeX kernel defines \usepackage to issue an error message initially, and \documentclass is defined as
\def\documentclass{%
\let\documentclass\@twoclasseserror % a second \documentclass command produces an error
\if@compatibility\else\let\usepackage\RequirePackage\fi % define \usepackage to be the same as \RequirePackage
\@fileswithoptions\@clsextension}
From a technical point \usepackage is first defined to the error message \usepackage before \documentclass but than set to the definition of \RequirePackage by the \documentclass before the class file is loaded.
You can use \RequirePackage before \documentclass, which might be sometimes required.
However, the true difference is the logical usage: \usepackage is an user macro intended for the document file while \RequirePackage is intended for package and class files to describe dependencies. Using \usepackage inside a package will also work, as long it isn't loaded with \RequirePackage before \documentclass. :-)
\usepackage), do nothing.".
– SeSodesa
May 24 '19 at 11:38
you can use \RequirePackage before the \documentclass statement, which has some advantages in some special cases.
Both expand to \@fileswithoptions \@pkgextension. I.e., no difference.
\usepackage is first defined to an error message but than \let\usepackage\RequirePackage is executed by \documentclass.
– Martin Scharrer♦
Jun 5 '11 at 9:23
fix-cm package that should be loaded via \RequirePackage before the \documentclass: bakoma-tex.com/doc/latex/base/fixltx2e.pdf But tex.stackexchange.com/questions/360656/… makes a good case for a second.
– TH.
Feb 26 '18 at 4:09
RequirePackage{hyperref}?) Take great care if youRequirePackage{hyperref}in some package. It had better be the last package you need. – David Hammen Jun 5 '11 at 19:42