sed? escaping back slash

[Craig Allsop]

Hi.

Is this the correct behaviour for sed?

echo test | sed "s/test/\\/"

Under 4dos shell in Win98, Cygwin GNU version v1.18 gives: \
Under 4dos shell in Win98, Cygwin GNU version v3.02 gives: char 9:
Unterminated 's' command

echo test | sed "s/test/\\\/"

Gives: \

Furthermore, if I wanted two back slashes in my replacement string, I try:

echo test | sed "s/test/\\\\/"

This results in only one slash. I need to use either seven or eight
backslashes to get just two in my substitution.

Under Linux, GNU sed version 2.05 same problem.
Under Linux, GNU sed version 3.02 same problem.

As far as I can see in the documentation, I need only supply one back slash
to escape a backspace in the replacement string.

Craig.