Take the 2-minute tour ×  While reading about packages that
allow to hook macros to certain events, I came across this
command, \shipout. Searching on the internet didn't help a lot
but if I'm not so wrong it's somehow related to creating new
pages (or is it?).  My question is, what is exactly \shipout,
what does it do and how it does what it does? (i.e. what is
happening on the low-level in the background)  share|improve
this question \shipout is apparently primitive, because
\show\shipout produces > \shipout=\shipout. –  Henri Menke Dec
27 '13 at 12:54 add comment  2 Answers  up vote 9 down vote
accepted  This is quite easy: \shipout is a primitive. Its
syntax is  \shipout ⟨box⟩  where ⟨box⟩ is completely specified
at page 278 of the TeXbook:  ⟨box⟩ → \box⟨8-bit number⟩ |
\copy⟨8-bit number⟩   | \lastbox | \vsplit⟨8-bit number⟩ to
⟨dimen⟩   | \hbox⟨box specification⟩{⟨horizontal mode material⟩}
  | \vbox⟨box specification⟩{⟨vertical mode material⟩}   |
\vtop⟨box specification⟩{⟨vertical mode material⟩} ⟨box