Great for quick and dirty stuff... I use it a lot to translate the output
of one thing into another on the fly.
mysql foo -e 'select bar from foo' | perl -e 'while(<>){chomp;qq`INSERT INTO
test values("$_");\n`}'|mysql test2
stuff like that... very handy.
On Wed, Feb 01, 2006 at 01:50:59PM -0800, Stephen A. Jarjoura wrote:
> Thanks, Anthony!
>
> So, localizing '@ARGV' also undefines it, allowing '<>' to be automagically
> defined as STDIN. Got it.
>
> Personally, I think I would have written it like this ...
> ===START=CODE===
> sub getParameters {
> my $parm_list = do { local $/; <STDIN> };
> }
> ===END=CODE===
>
> It reads clearer (to me, at least).
>
> ~SAJ
>
> "Anthony R. J. Ball" <[EMAIL PROTECTED]> wrote:
> from perldoc perlop
>
> The null filehandle <> is special: it can be used to emulate the
> behavior of sed and awk.
> Input from <> comes either from standard input, or from each file
> listed on the command line.
> Here's how it works: the first time <> is evaluated, the @ARGV array
> is checked, and if it is
> empty, $ARGV[0] is set to "-", which when opened gives you standard
> input. The @ARGV array is
> then processed as a list of filenames. The loop
>
> while (<>) {
> ... # code for each line
> }
>
> is equivalent to the following Perl-like pseudo code:
>
> unshift(@ARGV, '-') unless @ARGV;
> while ($ARGV = shift) {
> open(ARGV, $ARGV);
> while () {
> ... # code for each line
> }
> }
>
> except that it isn't so cumbersome to say, and will actually work. It
> really does shift the
> @ARGV array and put the current filename into the $ARGV variable. It
> also uses filehandle ARGV
> internally--<> is just a synonym for , which is magical. (The pseudo
> code above doesn't
> work because it treats as non-magical.)
>
> You can modify @ARGV before the first <> as long as the array ends up
> containing the list of
> filenames you really want. Line numbers ($.) continue as though the
> input were one big happy
> file. See the example in "eof" in perlfunc for how to reset line
> numbers on each file.
>
>
> On Wed, Feb 01, 2006 at 01:39:06PM -0800, Stephen A. Jarjoura wrote:
> > Hello, all;
> >
> > I am debugging code written by someone else, and noticed the following:
> > ===START=CODE===
> > sub getParameters {
> > my $parm_list = do { local(@ARGV,$/); <> };
> > }
> > ===END=CODE===
> >
> > This does what the author expected (slurp STDIN into the scalar
> > "$parm_list") but I was surprised by the "<>" as a stand-in for so I
> > looked it up. Here is what I found:
> > http://perldoc.perl.org/perlvar.html
> > ===START=PASTE===
> > ARGV
> >
> > The special filehandle that iterates over command-line filenames in @ARGV .
> > Usually written as the null filehandle in the angle operator <> . Note that
> > currently ARGV only has its magical effect within the <> operator;
> > elsewhere it is just a plain filehandle corresponding to the last file
> > opened by <> . In particular, passing \*ARGV as a parameter to a function
> > that expects a filehandle may not cause your function to automatically read
> > the contents of all the files in @ARGV .
> >
> > $ARGV
> >
> > contains the name of the current file when reading from <>.
> > ===END=PASTE===
> >
> > I could find no reference to "<>" as a synonym for "" ... am I missing
> > something obvious? [The code works, so obviously it is my knowledge that is
> > faulty.] If someone could point me at a reference or doc or faq, I'd be
> > grateful.
> >
> > Also, is there any particular reason (in the example given above) why
> > '@ARGV' would need to be localized, or is the author just being overly
> > cautous?
> >
> > Thanks, in advance, for your input!
> >
> > ---
> > Stephen ~runester~ Jarjoura
> > http://runester.com
> > http://boston.pm.org/kwiki/index.cgi?StephenJarjoura
> >
> >
> >
> > _______________________________________________
> > Boston-pm mailing list
> > [email protected]
> > http://mail.pm.org/mailman/listinfo/boston-pm
> >
>
> --
> www.suave.net - Anthony Ball - [EMAIL PROTECTED]
> OSB - http://rivendell.suave.net/Beer
> -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
> "Now cut that out!!" - Jack Benny
>
>
>
>
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--
www.suave.net - Anthony Ball - [EMAIL PROTECTED]
OSB - http://rivendell.suave.net/Beer
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Lawyer: a cat who settles disputes between mice.
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