5.16 Line Continuation

When filling is enabled, input and output line breaks generally do not correspond. The roff language therefore distinguishes input and output line continuation.

Escape sequence: \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.

Escape sequence: \c

Register: \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.

• If filling is enabled, 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.
  

• If filling is disabled, 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.
  

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