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我想使用 Perl 逐行解析外部程序（一些 shell 命令）的输出。该命令连续运行，因此我将其放入一个线程并使用共享变量与我的主程序进行通信。

到目前为止，我的代码看起来类似于

#!/usr/bin/perl

use warnings;
use strict;
use threads;
use threads::shared;

my $var :shared; $var="";

threads->create(
    sub {
        # command writes to stdout each ~100ms
        my $cmd = "<long running command> |";
        open(README, $cmd) or die "Can't run program: $!\n";
        while(<README>) {
            my $line = $_;
            # extract some information from line
            $var = <some value>;
            print "Debug\n";
        }
        close(README);
    }
);

while(1) {
    # evaluate variable each ~second
    print "$var\n";
    sleep 1;
}

对于某些命令，这工作得非常好，并且行在它们进入时被处理。输出将类似于：

...
Debug
Debug
...
<value 1>
...
Debug
Debug
...
<value 2>
...

但是，对于其他命令，这表现得很奇怪，并且正在逐块处理这些行。所以$var不会更新，Debug也不会打印一段时间。然后，突然输出是（类似于）：

...
<value 1>
<value 1>
<value 1>
...
Debug
Debug
Debug
...
<value 20>

并$var设置为最后/当前值。然后重复。解析总是延迟并在块中完成，而$var在两者之间不更新。

首先：除了使用管道之外，还有什么更好/更合适的方法来解析外部程序的输出（逐行！）？

如果没有，我该如何避免这种行为？

我读过，使用autoflush(1);或$|=1;可能是一种解决方案，但仅适用于“当前选择的输出通道”。我将如何在我的上下文中使用它？

先感谢您。

4

2 回答 2

0

In the general case, your script cannot change the buffering of the child process' output. In some specific cases you may be able to do so by starting it with appropriate switches, but that's about it.

I would recommend that instead of writing your own code to do the running and reading, you re-write your script to use the IPC::Run module. It exists to solve exactly this sort of problem. The documentation isn't the best ever, but the module itself is well-tested and solid.

于 2014-09-24T08:52:14.893 回答
0

感谢ikegami和Calle Dybedahl，我为我的问题找到了以下解决方案：

#!/usr/bin/perl

use warnings;
use strict;
use threads;
use threads::shared;
use sigtrap qw(handler exit_safely normal-signals stack-trace error-signals);
use IPC::Run qw(finish pump start);

# define shared variable
my $var :shared; $var="";

# define long running command
my @cmd = ('<long running command>','with','arguments');
my $in = '';
my $out = '';
# start harness
my $h = start \@cmd, '<pty<', \$in, '>pty>', \$out;

# create thread
my $thr = threads->create(
    sub {
        while (1) {
            # pump harness
            $h->pump;
            # extract some information from $out
            $var = <some value>;
            # empty output
            $out = '';
        }
    }
);

while(1) {
    # evaluate variable each ~second
    print "$var\n";
    sleep 1;
}

sub exit_safely {
    my ($sig) = @_;
    print "Caught SIG $sig\n";
    # harness has to be killed, otherwise
    # it will continue to run in background
    $h->kill_kill;
    $thr->join();
    exit(0);
}

exit(0);
于 2014-09-24T14:41:18.187 回答