Line Continuation (The GNU Troff Manual)

### 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