Do I need escape --? capture the line contain the string "--glob"

[jianhe-fun]

The following two command failed.
rg --help | rg "--glob"

rg --help | rg '--glob'

pretty sure there is an line in help section contain string "--glob". How can I capture that line?

[s-p-turner]

rg --help | rg "\-\-glob"

[BurntSushi]

That is one way. Although note that you only need to escape the first dash, so rg --help | rg '\--glob' will work. Another way is rg --help | rg -e --glob.

@jianheMark Note this bit from the man page and rg --help:

    <PATTERN>    
            A regular expression used for searching. To match a pattern beginning with a
            dash, use the -e/--regexp flag.
            
            For example, to search for the literal '-foo', you can use this flag:
            
                rg -e -foo
            
            You can also use the special '--' delimiter to indicate that no more flags
            will be provided. Namely, the following is equivalent to the above:
            
                rg -- -foo

[s-p-turner]

Other characters to be aware of are * (which signifies the matching of zero or more occurrences of any characters) and . (which signifies the matching of one occurrence of any character). You have to be wary of searching for strings containing literal * or . characters because the result might not match what you expect.

For example (incorrect if you're looking for a literal asterisk):

$ echo " SPT " | rg -e "SPT*"
1: SPT

One way to correct this would be to escape the asterisk:
$ echo " SPT " | rg -e "SPT\*"

A further example (again, incorrect if you're looking for a literal period):

$ echo " SPT " | rg -e "SPT."
1: SPT

One way to correct this would be to escape the period:

$ echo " SPT " | rg -e "SPT\."

[BurntSushi]

Yes, although that's somewhat of a separate issue than why rg --glob doesn't work. The issue with rg --glob is that the arg parser doesn't know the difference between a - that indicates a flag or a - that starts a pattern. That's why -e --glob works: -e signals to the arg parser that the next argument should be treated as a value for the -e flag, regardless of whether it starts with a dash. For example rg '[-]-glob' works. So does rg -- --glob, since -- signals to the parser that all subsequent arguments are positional and not flags.

For the general issue of escaping regex meta characters, see also the -F flag.