5.5.3.1 Comments

Probably one of the most¹³ common forms of escapes is the comment.

Escape: \"

Start a comment. Everything to the end of the input line is ignored.

This may sound simple, but it can be tricky to keep the comments from interfering with the appearance of the final output.

If the escape is to the right of some text or a request, that portion of the line is ignored, but the space leading up to it is noticed by gtroff. This only affects the ds and as request and its variants.

One possibly irritating idiosyncracy is that tabs must not be used to line up comments. Tabs are not treated as whitespace between the request and macro arguments.

A comment on a line by itself is treated as a blank line, because after eliminating the comment, that is all that remains:

Test
\" comment
Test

produces

Test

Test

To avoid this, it is common to start the line with .\", which causes the line to be treated as an undefined request and thus ignored completely.

Another commenting scheme seen sometimes is three consecutive single quotes (''') at the beginning of a line. This works, but gtroff gives a warning about an undefined macro (namely ''), which is harmless, but irritating.

Escape: \#

To avoid all this, gtroff has a new comment mechanism using the \# escape. This escape works the same as \" except that the newline is also ignored:

Test
\# comment
Test

produces

Test Test

as expected.

Request: .ig [end]

Ignore all input until gtroff encounters the macro named .end on a line by itself (or .. if end is not specified). This is useful for commenting out large blocks of text:

text text text...
.ig
This is part of a large block
of text that has been
temporarily(?) commented out.

We can restore it simply by removing
the .ig request and the ".." at the
end of the block.
..
More text text text...

produces

text text text…  More text text text…

Note that the commented-out block of text does not cause a break.

The input is read in copy-mode; auto-incremented registers are affected (see Auto-increment).