Keith> with (this is just off the top of my head; one can probably be more
Keith> efficient about it)

Keith> ls [filespec] |perl -ple unlink

That's scarily bad.  I have something akin to my once-famous "useless use of
cat award" that I used to give out for "dangerous use of ls".  You've just
triggered it for me.

Here's the point.  When you say:

  ls *.c

The following happens:

1) the shell expands *.c, into say: aaa.c, bbb.c, ccc.c
2) the shell fires up "ls aaa.c bbb.c ccc.c"
3) ls wakes up, and says "oh, I have command line args... let's go list those"
4) ls verifies aaa.c is there, and it's a file, so it prints it out
5) ls verifies bbb.c is there, and it's a file, so it prints it out
6) ls verifies ccc.c is there, and it's a file, so it prints it out

Why the heck would you make both the shell *and* ls go figure out what files
those are?

And don't get me started about what would have happened if you had a directory
that matched *.c.  That's a total tangent here, and also bad.

Now, let's go on to the dangerous part, more than just the wasted-CPU part.

"perl -ple" reads newline delimited names.  (By the way, it also needlessly
prints them... maybe you wanted "-nle".)

Suppose you have a file with a name of "aaa\nbbb.c".  Yup, that's legal.
Now your ls will print:

   aaa
   bbb.c

but Perl sees those as two separate names.  If you have an "aaa",
whoops, I mean, "now that you had an aaa", because it's now gone, even
though it didn't match "*.c".

Oops.

So, slow, and needlessly dangerous.  Bad all around.

Here's what I think you *might* have meant:

  perl -e 'unlink @ARGV' [filespec]

1) no useless use of ls
2) no danger from filenames containing newlines
3) no firing off two processes to do what one can do

And they say shell programming is simple.  {sigh}

--
Randal L. Schwartz - Stonehenge Consulting Services, Inc. - +1 503 777 0095
<mer...@stonehenge.com> <URL:http://www.stonehenge.com/merlyn/>
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