Help for using mylatex or mylatexformat?

Question

I have several document of the form

\documentclass{article}

\usepackage{package1}
\usepackage{package2}
\usepackage{package3}

\makeatletter
% some macros
\makeatletter

\begin{document}
\input{...}
\end{document}

What is the procedure to use mylatex or mylatexformat?

Answer 1

It helps to have a real example rather than fake code as in the question:

myfile.tex

\documentclass{article}

\usepackage{tikz}
\usepackage{siunitx}
\usepackage{pstricks}

\makeatletter
% some macros
\makeatletter

\begin{document}
hello
\end{document}

Then the comments in mylatex.ltx should be clear enough except that initex is accessed as pdflatex --ini these days usually

This loads all the packages and makes a format

$ pdflatex --ini  \&pdflatex  mylatex.ltx myfile

This typesets the document, without needing to load the packages.

pdflatex \&mylatex myfile

The log shows:

This is pdfTeX, Version 3.14159265-2.6-1.40.16 (TeX Live 2015) (preloaded format=mylatex 2015.9.23)  23 SEP 2015 12:56
entering extended mode
 restricted \write18 enabled.
 %&-line parsing enabled.
**&mylatex myfile
(./myfile.tex
LaTeX2e <2015/10/01>
Babel <3.9m> and hyphenation patterns for 79 languages loaded.
CUSTOMISED FORMAT. Preloaded files:
        .
 article.cls    2014/09/29 v1.4h Standard LaTeX document class
  size10.clo    2014/09/29 v1.4h Standard LaTeX file (size option)
    tikz.sty    2015/08/07 v3.0.1a (rcs-revision 1.151)
     pgf.sty    2015/08/07 v3.0.1a (rcs-revision 1.15)
  pgfrcs.sty    2015/08/07 v3.0.1a (rcs-revision 1.31)
everyshi.sty    2001/05/15 v3.00 EveryShipout Package (MS)
  pgfrcs.code.tex
 pgfcore.sty    2010/04/11 v3.0.1a (rcs-revision 1.7)
graphicx.sty    2014/10/28 v1.0g Enhanced LaTeX Graphics (DPC,SPQR)
  keyval.sty    2014/10/28 v1.15 key=value parser (DPC)
graphics.sty    2014/10/28 v1.0p Standard LaTeX Graphics (DPC,SPQR)
    trig.sty    1999/03/16 v1.09 sin cos tan (DPC)
graphics.cfg    2010/04/23 v1.9 graphics configuration of TeX Live
  pdftex.def    2011/05/27 v0.06d Graphics/color for pdfTeX
infwarerr.sty    2010/04/08 v1.3 Providing info/warning/error messages (HO)
 ltxcmds.sty    2011/11/09 v1.22 LaTeX kernel commands for general use (HO)
  pgfsys.sty    2014/07/09 v3.0.1a (rcs-revision 1.48)
  pgfsys.code.tex
pgfsyssoftpath.code.tex    2013/09/09  (rcs-revision 1.9)
pgfsysprotocol.code.tex    2006/10/16  (rcs-revision 1.4)
  xcolor.sty    2007/01/21 v2.11 LaTeX color extensions (UK)
   color.cfg    2007/01/18 v1.5 color configuration of teTeX/TeXLive
 pgfcore.code.tex
pgfcomp-version-0-65.sty    2007/07/03 v3.0.1a (rcs-revision 1.7)
pgfcomp-version-1-18.sty    2007/07/23 v3.0.1a (rcs-revision 1.1)
  pgffor.sty    2013/12/13 v3.0.1a (rcs-revision 1.25)
 pgfkeys.sty    
 pgfkeys.code.tex
 pgfmath.sty    
 pgfmath.code.tex
  pgffor.code.tex
    tikz.code.tex
 siunitx.sty    2015/09/14 v2.6l A comprehensive (SI) units package
   expl3.sty    2015/09/11 v6002 L3 programming layer (loader) 
expl3-code.tex    2015/09/11 v6002 L3 programming layer 
l3unicode-data.def    2015/07/20 v5676 L3 Unicode data
l3pdfmode.def    2015/09/10 v5983 L3 Experimental driver: PDF mode
  xparse.sty    2015/09/11 v6001 L3 Experimental document command parser
 amstext.sty    2000/06/29 v2.01
  amsgen.sty    1999/11/30 v2.0
   array.sty    2014/10/28 v2.4c Tabular extension package (FMi)
l3keys2e.sty    2015/09/11 v6001 LaTeX2e option processing using LaTeX3 keys
translator.sty    2010/06/12 ver 1.10
translator-language-mappings.tex
pstricks.sty    2013/12/12 v0.60 LaTeX wrapper for `PSTricks' (RN,HV)
   ifpdf.sty    2011/01/30 v2.3 Provides the ifpdf switch (HO)
pstricks.tex    2015/09/11 v2.63 `PSTricks' (tvz,hv)
pst-xkey.tex    2005/11/25 v1.6 PSTricks specialization of xkeyval (HA)
 xkeyval.sty    2014/12/03 v2.7a package option processing (HA)
 xkeyval.tex    2014/12/03 v2.7a key=value parser (HA)
  pst-fp.tex    2015/09/11 v2.63 `PST-fp' (hv)
        .
(./myfile.aux)