Major macro packages may require TeX to process many thousands of lines of macros, and open and read scores of font files, all of which would contribute to a sizable startup overhead if the job had to be done every time TeX was run. initex allows TeX to do the job once, and then save the results in a binary format file that can be later loaded more rapidly by virtex.
initex is normally required only at the time TeX is installed, or whenever major macro packages are updated. Thus, it will be rare for anyone but system installers to invoke it. Nevertheless, it is just a normal program without special privileges, so ordinary users can use it to prepare a private format file.
Here is how you can ask initex to prepare format files for several major packages:
For plain tex:
initex 'plain \\dump' mv plain.fmt tex.fmtThe single quotes are necessary to protect the backslash from interpretation as a Unix shell escape character.
For amstex:
initex '&tex amstex \\dump'The single quotes around the first argument protect the ampersand from interpretation as a Unix shell background request.
For etex:
initex '&tex eplain \\dump' mv eplain.fmt etex.fmt
For lamstex:
initex '&tex amstexl \\input lamstex \\dump' mv amstexl.fmt lamstex.fmt
For latex:
initex 'lplain \\dump' mv lplain.fmt latex.fmt
For slitex:
initex 'splain \\dump' mv splain.fmt slitex.fmt
For texinfo:
initex '&tex texinfo @dump'The last argument is different from the previous examples because texinfo redefines the TeX escape character from backslash to at-sign. As for amstex, the file tex.fmt must already be available.
Note that several of these require that the format file for plain TeX be available, since the first argument word &tex asks for the loading of the file tex.fmt.
It does not matter whether the command-line arguments are passed as a single argument, or as separate arguments, since TeX reconstructs the command line anyway.