how to pass a flag as an argument to grep

Question

I'm trying to pass -- as an argument to grep because the file I'm interested in contains -- within its text, like so

grep -- file.txt

but I cannot because grep sees -- as a flag. How do I pass -- as an argument, rather than a flag, to grep?

Answer 1

grep -e '--' file.txt

From the man page for grep:

-e PATTERN, --regexp=PATTERN
     Use PATTERN as the pattern.  This can be used to specify multiple search patterns, or to
     protect a pattern beginning with a hyphen (-).  (-e is specified by POSIX.)

Answer 2

At least with GNU grep you can tell it that no more flags are forthcoming with --. You can test it like this with a recent version of bash:

<<<"--" grep -- --

Output:

--