在perl中打開文件進(jìn)行寫操作，是不是只有在關(guān)閉文件句柄后，才會(huì)把內(nèi)容寫入到文件中。

ldorothy

請(qǐng)教各位一個(gè)問(wèn)題，在perl中打開文件進(jìn)行寫操作，是不是只有在關(guān)閉文件句柄后，才會(huì)把內(nèi)容寫入到文件中。

yashiro_lj

真正什么時(shí)候?qū)�，跟OS的讀寫策略有關(guān)，一般OS會(huì)等buffer到了一定大小再一次性寫入，當(dāng)然你也可以aotuflush強(qiáng)制實(shí)時(shí)寫入

就這個(gè)問(wèn)題來(lái)說(shuō)，什么時(shí)候?qū)懳募�和關(guān)閉文件句柄貌似沒有多大關(guān)系

Perl_Er

$|

If set to nonzero, forces a flush right away and after every write or print on the currently selected output channel. Default is 0 (regardless of whether the channel is really buffered by the system or not; $| tells you only whether you've asked Perl explicitly to flush after each write). STDOUT will typically be line buffered if output is to the terminal and block buffered otherwise. Setting this variable is useful primarily when you are outputting to a pipe or socket, such as when you are running a Perl program under rsh and want to see the output as it's happening. This has no effect on input buffering. See getc for that. (Mnemonic: when you want your pipes to be piping hot.)

ldorothy

謝謝兩位，我先弄弄

ldorothy

用了$|,可是還不是我想要的結(jié)果。當(dāng)下面的程序在執(zhí)行中，被強(qiáng)制kill了，是否f.txt文件里什么內(nèi)容都沒有。
#!/usr/bin/perl -w
open HANDLE, ">>f.txt";
$num = 1;
$| = 1;
while ($num < 10)
{
        print HANDLE "($num)'s\n";
        $num++;
        sleep 1;
}
close HANDLE;

Perl_Er

use IO::File;

    $fh = new IO::File;
    if ($fh->open(">file.txt")) {
        print $fh "hello";
        $fh->autoflush(1);
        sleep 6;
        $fh->close;
    }

yashiro_lj

把$| = 1改成select((select(HANDLE), $| = 1)[0])

或者use IO::Handle;再把$| = 1改成HANDLE->autoflush都可以實(shí)時(shí)寫文件

Perl_Er

http://perldoc.perl.org/functions/select.html

ldorothy

謝謝Perl_Er 和yashiro_lj 。
要多多努力學(xué)習(xí)了。謝謝前輩們