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I am using the %&format magic line in a plain TeX file. On older versions of TeX the result produces the expected results. On TeXLive 2009 (under Gentoo), however, this line has no effect. When I use 'tex -fmt format.fmt file.tex' the expected font substitutions nevertheless work. Has the magic file feature to be enabled in some config file? Many thanks.

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I don't know about Gentoo, but this is controlled by the parse_first_line option. For me, it lives in /.../texlive/2010/texmf/web2c/texmf.cnf. That said, changes should go in /.../texlive/2010/texmf.cnf:

parse_first_line = t
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or use command line option [-no]-parse-first-line – Martin Heller Oct 20 '10 at 22:37

Thanks for the speedy reply. In Gentoo the file is /etc/texmf/web2c/texmf.cnf. In there, parse_first_line was set true by default, but parse_first_line.tex was set to false. Changing to true ('t') fixed the problem. Great help!

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You should add that as a comment rather than an answer. – TH. Oct 20 '10 at 23:01
@TH: I don't think he has the rep to do that yet. – SamB Nov 30 '10 at 3:09
By the way, Michael, it is probably a good idea to associate an openid with your account in case you lose the cookie. (Assuming, of course, that you have not already lost it.) – SamB Nov 30 '10 at 3:14

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