thanks Chris, for a lovely explanation. This is the kind of explanation us MacOS-newbies understand. You should write a" Perl for MacOS X" book in the tradition of Randal's llama book. I'll buy it.
Btw, one quickie -- > move the LWP head to a better name, let's say /usr/bin/lwp-head by LWP head, I am assuming you are referring to HEAD, no? pk/ On Wednesday, April 3, 2002, at 09:04 AM, Chris Devers wrote: > On Wed, 3 Apr 2002, Puneet Kishor wrote: > >> Question -- if/when I do find head on the OS X CD, where should I put >> it? I can't put it back in /usr/bin because it will then overwrite HEAD >> that is present there now, no? > > * Find it on the CD, let's say it's at /Volumes/MacOSX/usr/bin/head > * move the LWP head to a better name, let's say /usr/bin/lwp-head > * copy /Volumes/MacOSX/usr/bin/head to /usr/bin/head > > System restored, conflict resolved. > >> corollary -- why is head so important? > > It's useful for viewing slices of an input stream or file. Yes it is the > opposite of tail, and in tandem the two can help solve problems like, > say, > (contrived example) finding the median sized file in a directory: > > % ls -s1 | sort | wc -l > 51 > % ls -s1 | sort | head -26 | tail -1 > 42 echelon_terms > % > > Yes that's kind of an exotic example, but it's the first one that comes > to > mind that shows how you can pass output from head (the first subset of a > list of lines) to tail (to get the last sub-subset of the head list) in > order to slice into the middle of a larger set. > > Plus, more simply, they're just not the same. /usr/bin/head gives you > the > beginning of input; /usr/bin/tail gives you the end of input. They are > complementary, yes, but they do have different roles & uses. > > Anyway, if you're not normally slicing & dicing files & streams, then > you > can probably live without filters like this, but they can be very useful > if you know how to manipulate them. And as you point out, even if you > don't use them directly, other applications might assume that the tools > are available & fail if they're not. So it's worth fixing. > > > > -- > Chris Devers [EMAIL PROTECTED] > Apache / mod_perl / http://homepage.mac.com/chdevers/resume/ > > "More war soon. You know how it is." -- mnftiu.cc >
