I have a .sty file that may be loaded using the command \usepackage (in LaTeX) or the command \input (in LaTeX or Plain TeX).

Is there any way that within the .sty file to check which command was used to load the file?

  • 4
    \usepackage will define the csname ver@nameofyoursty.sty. You could test for it. Nov 17 '18 at 16:22
  • 1
    You can also check the used format (provided your package should behave the same in LaTeX independent on the used method to load it).
    – Skillmon
    Nov 17 '18 at 16:56
  • 1
    You might take a look at \@ifpackageloaded. Presumably it is set by \usepackage, not \input. Nov 17 '18 at 18:32
  • Thanks all, your explanations really solved my problem. Nov 18 '18 at 7:19

As TeX is a macro expansion language, you cannot know what the 'context' of a macro is: there simply isn't one. Also, \input (or \@@input) can be used within LaTeX. What you can do is check for the format or some marker macro. For example, in expl3-generic.sty we check \fmtname

  % LaTeX
  % Not LaTeX

A common approach is to check for the existence of something like \documentclass

  % Not LaTeX
  % LaTeX

although this will also be true when things like miniltx are loaded. So it depends exactly what you need to know. Some packages are fine with miniltx, others perhaps not.

  • I see how this would distinguish plain TeX from LaTeX. But I think OP was asking about distinguishing \usepackage from \input, both within LaTeX.
    – Teepeemm
    Jan 22 '19 at 23:32
  • @Teepeemm Which I hope was addressed by my first line: you can't know (you can check for e.g. \ver@<filename> but of course someone might make that manually and still use \input.
    – Joseph Wright
    Jan 23 '19 at 7:36
  • But if someone goes to the trouble of \makeatletter/other to manually define \ver@<filename>, they know what they're doing and deserve whatever happens. The comments on the original post also hint at two other ways to check. Could we spell out exactly how to do so? If necessary, we could also spell out how those methods could be foiled.
    – Teepeemm
    Jan 23 '19 at 15:15

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