Hi David, On Wed, 08 May 2013 19:37:30 -0700 David Christensen <dpchr...@holgerdanske.com> wrote:
> I wrote: > >> $| = 1; # [1] $OUTPUT_AUTOFLUSH > > On 05/08/13 02:24, Shlomi Fish wrote: > > http://perl-begin.org/tutorials/bad-elements/#properly_autoflushing > > Which recommends: > > use IO::Handle; > STDOUT->autoflush(1); > > 1. For larger, longer-lived, shared, portable, "serious", "Modern > Perl", etc., programs, that way is better. > > 2. I saw the OP's requirements as being met by a short "throw-away" > script that wouldn't be kept or distributed. $| is fast and cheap, and > it works. > Yes, and obscure. > 3. Part of gaining proficiency in Perl (and other Unix tools) is > learning the more commonly used special variables, such as $|, $?, $@, etc.. And an even further part of gaining proficiency is to know to make your code less obscure and less clever and more http://en.wikipedia.org/wiki/KISS_principle (not my own link!). > > 4. Autoflush might not be needed in this case. I put it in there as a > reminder for scripts that do need it. > OK. > > >> print `cat *>>foo.out`; # [2] qx// > > This is the same as «system('cat *>> foo.out')» (only more costly), and the > > command in this case should not emit any output (because it is redirected > > to a file). > > 1. I thought about: > > if (my $e = system('cat * >> foo.out')) { > # error handling > } > > But, a decent system() example should use the multi-argument list form. > That means I would have to redirect STDOUT first and glob the file > names in the argument list. Too much complexity for a "beginner" posting. Nothing wrong with a non-list call to system() if that is what you want and need (as long as you say why you intend to do that and use precautions such as https://metacpan.org/release/String-ShellQuote ). Doing «print `...`» is silly. > > 2. Yes, cat's STDOUT ends up in foo.out and STDERR ends up on the > console. I put the "print" in there as much to make people say "WTF?", > look it up, and ponder it, thus reinforcing their knowledge of backticks. Please don't give people "WTF?" moments like that. I am an experienced programmer and your code gave me that. > > 3. The append redirect ">>" is a bug/ mis-feature -- foo.out will grow > every time the script is run, The user is required to delete foo.out > manually before running the script. The alternative, ">", destroys > data. Pick your poison. Yes. > > Furthermore, many non-UNIX-like systems don't contain a cat command. > > Thank God for electronics recycling. ;-) > What do you mean? Regards, Shlomi Fish -- ----------------------------------------------------------------- Shlomi Fish http://www.shlomifish.org/ Original Riddles - http://www.shlomifish.org/puzzles/ George: I guess you can enter now. I’m just following orders. SGlau: The Nuremberg defense! George: This place gives you no other option. — http://www.shlomifish.org/humour/Summerschool-at-the-NSA/ Please reply to list if it's a mailing list post - http://shlom.in/reply . -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
