I'm using Bourne shell (not bash). Well, not one of my expectations was realized. All others were wrong.

Code:

grep \$

Me: all lines with $ in them
Unix: all lines

Code:

grep \\$

Me: well, the first \ escapes the second \, so it's just a plain \. $ would need to be followed by an environmental variable, I suppose, but since it isn't, it's just plain $.
Unix: all lines with $ in them

Code:

grep \\\$

Me: all lines with \$ (literally) in them
Unix: all line with $ in them.

Code:

grep '\$'

Me: all lines with \$ (literally) in them
Unix: all lines with $ in them

Code:

grep '\'$'

Me: first it would show a secondary prompt, so I could finish the string. Then it would search for \$ (literally).
Unix: first it showed a secondary prompt, after finishing the string with an ', it said "error 41: No remembered search string."

Code:

grep \\

Me: all lines with \ in them
Unix: "error 50: Regular expression overflow."

Code:

grep \\\\

Me: a line with \\ (two \'s literally) in it
Unix: all lines with \ in them

Code:

grep "\$"

Me: all lines with $ in them
Unix: all lines

Code:

grep '"$'

Me: all lines with "$ in them
Unix: all lines with $ or $". I'm not sure.

Code:

grep "$"

Me: all lines with $ in them
Unix: all lines.

Maybe when I write $ by itself, the shell expands that into an empty string, therefore the search returns everything?

The others, I'm simply baffled.