Re: Using $ in quotes with characters after it

[Dan]

Interesting.  I missed that part of the man page where it says "?" loses
its meaning in basic grep.  Thanks for your time in helping me figure out
where exactly I went wrong.

On Sat, Mar 24, 2012 at 9:05 PM, Mike Frysinger <address@hidden> wrote:

> On Saturday 24 March 2012 15:06:00 Dan wrote:
> > This is the output after running `set -x`.  It looks like the shell is
> > behaving properly.  It's un-escaping the question mark when it's supposed
> > to be and it isn't when it isn't supposed to be.  Grep shouldn't be
> > producing that output though.  The only explanation I can think of is
> that
> > the wildcard is being too greedy and consuming all of the string.  But
> from
> > what I know that's not how it works.
>
> seems correct to me.  in the first two, grep gets a question mark with a
> backslash.  in the last one, it doesn't because the shell processed it
> first.
> if you read the man page, it says that in a basic regular expression (which
> you're doing because you didn't use -E or run egrep), a plain "?" has no
> meaning -- it's just another character.  grep needs to see the backslash to
> treat it specially.  further, the anchor characters ("$" and "^") only have
> meaning if they are in the last or first position respectively.  otherwise,
> they're just another character to match.
>
> hence, this command:
>        grep '^abc.*$\?' testfile
> means "anchor to the start of the line, then match abc, then match
> anything,
> then either anchor to the end of the line or don't".  so really, "$\?" at
> the
> end of the regexp is completely pointless.
>
> but this command:
>        grep ^abc.*$\? testfile
> means "anchor to the start of the line, then match abc, then match
> anything,
> then match a dollar sign, then match a question mark".
> -mike
>



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