When filling is enabled, input and output line breaks generally do not
correspond. The roff language therefore distinguishes input and
output line continuation.
\RET\RET (a backslash immediately followed by a newline)
suppresses the effects of that newline in the input. The next input
line thus retains the classification of its predecessor as a control or
text line. \RET is useful for managing line lengths in the
input during document maintenance; you can break an input line in the
middle of a request invocation, macro call, or escape sequence. Input
line continuation is invisible to the formatter, with two exceptions:
the | operator recognizes the new input line
(see Numeric Expressions), and the input line counter register
.c is incremented.
.ll 50n .de I . ft I . nop \\$* . ft .. Our film class watched .I The Effect of Gamma Rays on Man-in-the-Moon Marigolds. \" whoops, the input line wrapped .br .I My own opus begins on line \n[.c] \ and ends on line \n[.c].
⇒ Our film class watched The Effect of Gamma Rays on
⇒ Man-in-the-Moon Marigolds.
⇒ My own opus begins on line 11 and ends on line 12.
\c\n[.int] ¶\c continues an output line. Nothing after it on the input line
is formatted. In contrast to \RET, a line after \c
remains a new input line, so a control character is recognized at its
beginning. The visual results depend on whether filling is enabled; see
Manipulating Filling and Adjustment.
\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.
\c is
handled as a continuation of the same input text line.
.nf
This is a \c
test.
⇒ This is a test.
An intervening control line that causes a break overrides \c,
flushing out the pending output line in the usual way.
The .int register contains a positive value if the last output
line was continued with \c; this datum is associated with the
environment (see Environments).69