"platex" is a command used by Japanese-tex user.
I'm sorry.
There was two-byte blanks in my tex source
,though they aren't apparent in my e-mail.
When I removed them, everything was OK.
Below is a log when compiling a tex source with two-byte blanks.
$ platex 3.tex
This is e-pTeX, Version 3.14159265-p3.5-130605-2.6 (utf8.euc) (TeX Live 2015/dev/Debian) (preloaded format=platex)
restricted \write18 enabled.
entering extended mode
(./3.tex
pLaTeX2e <2006/11/10> (based on LaTeX2e <2014/05/01> patch level 0)
Babel <3.9l> and hyphenation patterns for 11 languages loaded.
(/usr/share/texlive/texmf-dist/tex/latex/base/article.cls
Document Class: article 2014/09/29 v1.4h Standard LaTeX document class
(/usr/share/texlive/texmf-dist/tex/latex/base/size10.clo))
(/usr/share/texlive/texmf-dist/tex/latex/amsmath/amsmath.sty
For additional information on amsmath, use the `?' option.
(/usr/share/texlive/texmf-dist/tex/latex/amsmath/amstext.sty
(/usr/share/texlive/texmf-dist/tex/latex/amsmath/amsgen.sty))
(/usr/share/texlive/texmf-dist/tex/latex/amsmath/amsbsy.sty)
(/usr/share/texlive/texmf-dist/tex/latex/amsmath/amsopn.sty))
(/usr/share/texlive/texmf-dist/tex/latex/amsfonts/amssymb.sty
(/usr/share/texlive/texmf-dist/tex/latex/amsfonts/amsfonts.sty))
LaTeX Warning: Unused global option(s):
[28pt,a4j].
(./3.aux) (/usr/share/texlive/texmf-dist/tex/latex/amsfonts/umsa.fd)
(/usr/share/texlive/texmf-dist/tex/latex/amsfonts/umsb.fd)
! Not two-byte family.
l.5 ( \alpha
\in \mathbb{C} )
?
! Not two-byte family.
l.5 ( \alpha \in
\mathbb{C} )
?
[1] (./3.aux) )
Output written on 3.dvi (1 page, 376 bytes).
Transcript written on 3.log.
Cheers,
EenyMeenyMinyMoa