(eplain.info)Diagnostics

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Enter node , (file) or (file)node

4.1 Diagnostics
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Plain TeX provides the '\tracingall' command, to turn on the maximum
amount of tracing possible in TeX.  The (usually voluminous) output from
'\tracingall' goes both on the terminal and into the transcript file.
It is sometimes easier to have the output go only to the transcript
file, so you can peruse it at your leisure and not obscure other output
to the terminal.  So, Eplain provides the command '\loggingall'.  (For
some reason, this command is available in Metafont, but not in TeX.)

   It is also sometimes useful to see the complete contents of boxes.
'\tracingboxes' does this.  (It doesn't affect whether or not the
contents are shown on the terminal.)

   You can turn off all tracing with '\tracingoff'.

   You can also turn logging on and off globally, so you don't have to
worry about whether or not you're inside a group at the time of command.
These variants are named '\gloggingall' and '\gtracingall'.

   Finally, if you write your own help messages (see '\newhelp' in 'The
TeXbook'), you want a convenient way to break lines in them.  This is
what TeX's '\newlinechar' parameter is for; however, plain TeX doesn't
set '\newlinechar'.  Therefore, Eplain defines it to be the character
'^^J'.

   For example, one of Eplain's own error messages is defined as
follows:

     \newhelp\envhelp{Perhaps you forgot to end the previous^^J%
        environment? I'm finishing off the current group,^^J%
        hoping that will fix it.}%