# Rationale to use \input{filename} on the pdflatex command line?

In a tex.SX user profile, I read the best practice recommendation

Execute pdflatex \input{filename} instead of pdflatex filename.

I have always used the latter one, directly, in scripts, and in Makefiles.

What would be a reason to always use pdflatex \input{filename} instead?

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you can ask Garbage Collector aka Adorable Creature herself in the chat, she is there from time to time. – yo' Feb 7 '13 at 11:31
Oh, I totally missed that I already have the "talk in chat" privilege now. – fbmd Feb 8 '13 at 21:37
Chatting requires "only" 20 pts :) – yo' Feb 8 '13 at 21:43
It should be meant as best typing practice. :-) – kiss my armpit Feb 13 '13 at 14:33
@GarbageCollector Turning a disadvantage to an advantage, clever! :-) – Heiko Oberdiek Feb 13 '13 at 17:06

• It is a good trick, if someone wants to put TeX code before. Examples:

pdflatex '\def\foo{bar}\input{filename}'
pdflatex '\includeonly{introduction}\input{filename}'


or inside \write18 (shell escape feature):

\immediate\write18{\detokenize{pdflatex '\def\foo{bar}\input{filename}'}}
\immediate\write18{\detokenize{pdflatex '\includeonly{introduction}\input{filename}'}}


e-TeX's \detokenize prevents the expansion of the macros inside \write, see question.

• Also LaTeX catches the error message a little better, because it checks for the file first and throws a proper error message.

The TeX behaviour of '\input' without braces or on the command line would be:

pdflatex filename

! I can't find file filename'.
<*> filename

(Press Enter to retry, or Control-D to exit)
Please type another input file name:


Then you can escape from there with Control-D (Unix) or Control-Z (Windows). or the file x.tex of LaTeX's tools bundle can be used for this purpose.

pdflatex '\input{filename}

Type X to quit or <RETURN> to proceed,
or enter new name. (Default extension: tex)

Enter file name:


Then LaTeX already looks for x or X as answer to abort the job.

Answer to a comment: However, in both variants an error message is thrown, if the file does not exist. An interactive prompt in a command chain (pdflatex test && do something) can be avoided by the pdfTeX options interaction=batchmode or --interaction=nonstopmode.

• It's longer than filename.
• The backslash needs special treatment (quoting, doubling) with many shells.

## Summary

IMHO the two described "advantages" are indeed too weak for always using pdflatex \input{test} over pdflatex test. At least I have tried to find possible reasons. And the trick with putting TeX stuff before \input is worth to be remembered.

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Still, these doesn't seem to me as advantages of pdflatex "\input{filename}", rather as features: You can do pdflatex "\def\foo{bar}\input{filename}" if you have a need for such trick. It is a bit like saying: You can use cat this way: cat file | sed 's///g' because this allows you to do cat file | sed 's/foo/bar/g' easily. – yo' Feb 7 '13 at 11:29
Well, saying cat file | sed ..., independently of what sed ends up doing, is a canonical example of a Useless Use Of Cat... :-) – Mariano Suárez-Alvarez Feb 7 '13 at 15:55
I am sorry, but I still don't get it. I use the \input trick quite a lot to put TeX code before when I need so, but what exactly is the advantage of a plain pdflatex \input{filename} over pdflatex filename, as asked by the OP? – Daniel Feb 13 '13 at 8:28
I really should try asking the user who stated this in the first place. I see the point in the answer, but advantage #1 is not as common to make a habit of \input{}, and advantage #2 breaks pdflatex file && do something bash chains with an interactive prompt. I still see no reason to always use it. – fbmd Feb 13 '13 at 9:51
That sounds acceptable. :) Would you add that to the answer? – fbmd Feb 13 '13 at 12:02