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The formatter permits configuration of the page length and page number.
Change (increase or decrease) the page length per the numeric expression
length. The default scaling unit is ‘v’. If length is
invalid, GNU troff
emits a warning in category ‘number’. If
length is absent or invalid, ‘11i’ is assumed. If
length is nonpositive, GNU troff
emits a warning in
category ‘range’ and sets the page length to the device’s vertical
motion quantum; recall Motion Quanta.
The read-only register ‘.p’ interpolates the current page length.
Change (increase or decrease) the page number of the next page
per the numeric expression num. If num is invalid, GNU
troff
emits a warning in category ‘number’ and ignores the
request. Without an argument, pn
is ignored.
The read-only register .pn
interpolates num if set by
pn
on the current page, or the current page number plus 1.
The formatter offers special support for typesetting headers and footers, collectively termed titles. Titles have an independent line length, and their placement on the page is not restricted.
'
left'
center'
right'
Format an output line as a title consisting of left, center,
and right, each aligned accordingly. The delimiter need not be a
neutral apostrophe: tl
accepts the same delimiters as most escape
sequences; see Delimiters. If not used as the delimiter, any
page number character character is replaced with the current page
number; the default is ‘%’; see the the pc
request below.
Without an argument, tl
is ignored. tl
writes the title
line immediately, ignoring any partially collected line.
It is not an error to omit delimiters after the first. For example, ‘.tl /Thesis’ is interpreted as ‘.tl /Thesis///’: it sets a title line comprising only the left-aligned word ‘Thesis’.
Change (increase or decrease) the line length used by titles per the
numeric expression length. The default scaling unit is ‘m’.
The formatter’s default title length is ‘6.5i’. If length is
invalid, GNU troff
emits a warning in category ‘number’ and
ignores the request. If length is nonpositive, GNU
troff
emits a warning in category ‘range’ and sets the
title line length to the device’s horizontal motion quantum; recall
Motion Quanta. The title length is is associated with the
environment (see Environments). If length is omitted, GNU
troff
restores the environment’s previous title length.
The read-only register ‘.lt’ interpolates the title line length.
Set the page number character to char. With no argument, the page
number character is disabled. pc
does not affect the
register %
.
The following example exercises title features.
.lt 50n This is my partially collected .tl 'Isomers 2023'%'Dextrose Edition' line. ⇒ Isomers 2023 1 Dextrose Edition ⇒ This is my partially collected line.
We most often see titles used in page header and footer traps. See Traps.
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