It is often useful to print out the values of variables in the log
file or on the terminal. Three possible ways to print out the
contents of \textheight variable are:
\showthe\textheight
\message{The text height is \the\textheight}
\typeout{The text height is \the\textheight}
\the (which provides
the value of a variable), \showthe (print a variable to the
terminal and the log, on a line of its own), and \message, which
interpolates something into the log. The command \typeout is
LaTeX’s general message output mechanism.
In each case, the variable’s value is printed as a number of points.
To typeset the value of \textheight, just
\the\textheight is enough, but a more flexible alternative is
to use the printlen package. Printlen allows you
to choose the units in which you print a variable; this is useful,
given that the most ordinary people don’t think in points
(particularly Knuth’s points, of which there are 72.27 to the inch).
So, using printlen, we could say:
\newlength{\foo}
\setlength{\foo}{12pt}
\verb|\foo| is \printlength{\foo}
and get:
\foo is 12pt
while, if we say:
\newlength{\foo}
\setlength{\foo}{12pt}
\uselengthunit{mm}
\verb|foo| is \printlength{\foo}
we get:
\foo is 4.21747mm
This answer last edited: 2012-03-16
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