[Cialug] Regular Expression for Pathnames

[Todd Walton]

Fabulous! I knew there was answer. Thanks, guys!

--
Todd


On Mon, Nov 24, 2014 at 1:43 PM, Daniel A. Ramaley <daniel.ramaley at drake.edu
> wrote:

> I realized right after sending it that the way your problem is stated,
> you might want to match different numbers of slashes. To match strings
> that have between 1 and 3 (inclusive) slashes, change the part between
> curly braces to be "1,3" instead of just "3":
>
>         egrep '^(/[^/]+){1,3}$'
>
> Explaining what this bit of line noise means:
>
> ^       Match beginning of line.
> ()      Groups stuff and treats it as one object.
> /       Match a literal "/".
> []      Matches a single character provided inside the brackets.
>         For example, "[abcde]" will match 5 lowercase letters.
> ^       If used as the first character in square brackets, this
>         inverts the characters matched.
> /       Match "/". Note that it is inverted due to the preceding
>         "^" and so therefore means match anything *except* "/".
> +       Match the [] expression 1 or more times.
> {}      Counter. How many times we should match.
> 1,3     Match between 1 and 3 times, inclusive.
> $       Match end of line.
>
> You can find more precise explanation in regex documentation; this is
> just off the top of my head. The most important thing with reading
> regexes is figuring out how they are grouped. The basic pattern here is
> the (foo){bar} which just means "match foo, bar number of times".
>
> On 2014-11-24 at 10:58:24 Ron Houk wrote:
> > Wow. Your solution is a lot more elegant. I'm still trying to learn
> > this stuff. :)
> >
> > On Nov 24, 2014 10:35 AM, "Daniel A. Ramaley"
> > <daniel.ramaley at drake.edu>
> > wrote:
> > > This should work for your purposes if all the data looks like the
> > > samples. Set the number between curly braces to whatever you need.
> > > (Note that your sample data didn't have any matches for just 2
> > > slashes, but does for 3 slashes.)
> > >
> > >         egrep '^(/[^/]+){3}$'
> > >
> > > On 2014-11-24 at 10:23:07 Todd Walton wrote:
> > > > If I have a text file full of pathnames, like:
> > > >
> > > > /var/log/folder1
> > > > /var/log/folder2
> > > > /home/todd/mydir
> > > > /var/log/folder1/fileh
> > > > /var/log/folder1/foldersub/fileh
> > > >
> > > > ...etc, what's the regular expression to find where a string has
> > > > exactly two (or however many) forward slashes to the left of it?
> > > > I
> > > > have a 360,000 line list of path names, and I'd like to find where
> > > > a
> > > > certain string falls early in the path.  I'm really only
> > > > interested
> > > > in paths where it's in the top three or four directories.
> > > >
> > > > --
> > > > Todd
> > > > _______________________________________________
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> > >
> > > __
> > > Daniel A. Ramaley  |  Network Engineer 2
> > > Drake Technology Services (DTS) | Drake University
> > >
> > > T: +1 515 271-4540
> > > F: +1 515 271-1938
> > > E: daniel.ramaley at drake.edu
> > >
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> __
> Daniel A. Ramaley  |  Network Engineer 2
> Drake Technology Services (DTS) | Drake University
>
> T: +1 515 271-4540
> F: +1 515 271-1938
> E: daniel.ramaley at drake.edu
>
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