Re: Globbing

[Michael Neumann <mneumann@xxxxxxxx>]

Rahul Siddharthan wrote:
> Bill Hacker wrote:
> > That said, I remain surprised that others haven't already said, and
> > sooner, rather than later, words to the effect:
> >
> > 'Yes, historical reasons quite aside, these common and frequently needed
> > tools can too often be more arcane than they need to be'.
>
> It always surprises me how much of the Unix Hater's Handbook remains
> valid.  
>
> For example, how do you use "find" to find all files in a directory
> that end in ".el" and don't have a corresponding ".elc" file?  
> Answer:
>  find . -name '*.el' -print  \
>     |sed 's/^/FOO=/' \
>     |sed 's/$/; if [ ! -f ${FOO}c ]; then echo $FOO; fi/'  \
>     | sh

Hm, why don't you use a "real" language, instead of hacking shell
scripts. I understand that they are useful in some cases, as /bin/sh is 
cross-platform and installed by default. For anything else, take perl, 
python or ruby. In Ruby this becomes the following:

  Dir['**/*.el'].reject {|f| File.exist?(f + "c")}.each {|f| puts f}

And that's just a simple example. Once it gets more complex, the
power of more advanced scripting languages pay off a lot more.

> When I want to do something like that to a large directory, I generate
> a full directory listing and then write a python program to parse it.
> That seems easier to wrap my mind around.  (The author of the above
> find command used emacs-lisp instead, then figured out the correct
> find incantation because it bothered him.  "It only took me 12 tries
> to get it right.  It only spawns two processes per file in the
> directory tree we're iterating over.  It's the Unix Way!")

If you have an Apple, you can use this one liner (because Ruby comes by 
default ;-)

find . -name "*.el" -print | ruby -lne 'puts $_ unless test(?e, $_ + "c")'

Regards,

  Michael