According to info groff (section 5.11 Character Translations),
\. should print just the dot. However, this is not what seems to happen.
If I render this manpage
.TH x x x x
\.SH foo
I get foo rendered as a section heading, and .SH is not printed.
So, why does this happen, and how do I escape the dot (and the apostrophe) at the begginning of the line in groff?
To escape dot at the beginning of line write use \[char46] :
\[char46]SH foo
prints
.SH foo
This is an expected behavior but should be fixed in manual page. Here is a bug report.
Below you can read the description of both \\ (shortened)
and \. (from info pages).
-- Escape: \\
[...]
`\\' is a `delayed' backslash; more precisely, it is the default
escape character followed by a backslash, which no longer has
special meaning due to the leading escape character. It is _not_
an escape sequence in the usual sense! In any unknown escape
sequence `\X' the escape character is ignored and X is printed.
But if X is equal to the current escape character, no warning is
emitted.
As a consequence, only at top-level or in a diversion a backslash
glyph is printed; in copy-in mode, it expands to a single
backslash which then combines with the following character to an
escape sequence.
[...]
-- Escape: \.
Similar to `\\', the sequence `\.' isn't a real escape sequence.
As before, a warning message is suppressed if the escape character
is followed by a dot, and the dot itself is printed.