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It is important to understand how gtroff
handles input and output
lines.
Many escapes use positioning relative to the input line. For example, this
This is a \h'|1.2i'test. This is a \h'|1.2i'test.
produces
This is a test. This is a test.
The main usage of this feature is to define macros that act exactly at the place where called.
.\" A simple macro to underline a word .de underline . nop \\$1\l'|0\[ul]' ..
In the above example, ‘|0’ specifies a negative distance from the
current position (at the end of the just emitted argument \$1
)
back to the beginning of the input line. Thus, the ‘\l’ escape
draws a line from right to left.
gtroff
makes a difference between input and output line
continuation; the latter is also called interrupting a line.
Continue a line. \RET
(this is a backslash at the end of a
line immediately followed by a newline) works on the input level,
suppressing the effects of the following newline in the input.
This is a \ .test ⇒ This is a .test
The ‘|’ operator is also affected.
\c
works on the output level. Anything after this escape on the
same line is ignored except \R
, which works as usual. Anything
before \c
on the same line is appended to the current partial
output line. The next non-command line after an interrupted line counts
as a new input line.
The visual results depend on whether no-fill mode is active.
nf
request), the next input
text line after \c
is handled as a continuation of the same input
text line.
.nf This is a \c test. ⇒ This is a test.
fi
request), a word interrupted
with \c
is continued with the text on the next input text line,
without an intervening space.
This is a te\c st. ⇒ This is a test.
Note that an intervening control line that causes a break is stronger
than \c
, flushing out the current partial line in the usual way.
The .int
register contains a positive value if the last output
line was interrupted with \c
; this is associated with the current
environment (see Environments).
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