Hi Alex!

At 2021-01-22T14:00:33+0100, Alejandro Colomar (man-pages) wrote:
> Why do some pages use \:/ for the slash in the path part of a URL, but
> some others don't, and just use /?

Laziness or ignorance of how URLs get typeset and what the \: escape is
for.

URLs are typeset with hyphenation disabled.  That means that the line
preceding a URL can
be broken early in a very ugly way, somewhat like this sentence.

Slashes in URLs turn out to be pretty good places to break a line if it
must be.  If you wanted a hyphen to appear at the break point, you'd use
the "hyphenation character", an escape that goes way back to 1970s AT&T
troff: \%.  However, as with URLs,sometimes you want a hyphenless break
point, and that's what groff's \: is.  Heirloom Doctools troff supports
\: as well.  mandoc 1.14.1 does not (it refuses to break URLs at all, at
least for man(7) documents; I didn't check its mdoc(7) support).

> Moreover, why do the former use \:/ only for the path, but not for the
> protocol?

I think it is because people feel like postponing a break by 7 more
characters to get the first part after the schema adjacent to it is not
too high a price to pay.

There's no deep reason why you couldn't do:

.UR http\:://www\:.w3\:.org\:/CGI
Common Gateway Interface
.UE

for instance.

House style for the groff man pages is to place hyphenless break points
_before_ periods and _after_ slashes in pathnames and URLs.  The former
point is one I'd recommend firmly to others, because it helps keep the
reader from confusing a line-broken pathname or URL as ending a
sentence (prematurely).  The latter convention is more arbitrary; plenty
of perfectly valid URLs (and pathnames) exist with or without trailing
slashes, so one can't infer the end of such an object from the presence
or absence of a slash at the end of a line of text.

Regards,
Branden