About Grep Escape

What’s the difference with grep '$id\$' and grep \$id\$?

The first will match string $id$, and the second will match the string ends with $id.

It turns out that, there’re two level of escape here.

The first is shell quote, as \ is also special characters in shell,
it will be interprated as an escapce character, and turns \$ into $ BEFORE it is sent to grep, so grep will actually get $id$ as input.
To it hehaves as we intended, we should use double slash \\, shell will remove the first slash, and send the second to grep.
To simplify things, use single quote is better choise, '$id$' will tell shell that $id$ should be treated as raw string.

The second is escape of grep itself. $ is special only if it resides in the end of string. So the first $ will be interprated literally, the second should be escaped. To make grep treat input as fixed string, -F option is a better choice.

All the above considerations sum up, we get the final command:

grep -F '$id$'