Perl 尊重 '<'作为常规字符而不是输出重定向 [英] Perl is respecting '<' as a regular character rather an output redirection

问题描述

我需要一些帮助来解决这个特定的编码问题.

I would like some help figuring this particular coding problem.

我有一个调用另一个 perl 脚本(#2)的 perl 脚本(#1).在#1 中，我调用#2 也将其输出重定向到日志文件.像这样

I have a perl script (#1) that calls another perl script(#2). In #1, I call #2 to also redirect its output to a log file. like so

my @command = ('downloadImage', '-url', $url, '>', $log);

此命令在终端上运行时运行良好.我是否必须使用其他类型的特殊字符来告诉 perl > 是输出重定向，而不仅仅是一些常规字符?

this commands runs fine when it runs on the terminal. Do I have to use some other kind of special character to tell perl that > is output redirection not just some regular character?

我运行它:

system(@command);

推荐答案

我假设完整的代码是:

my @command = ('downloadImage', '-url', $url, '>', $log);
system @command;

system 有两种模式.system $command 将在 shell 中运行 $command.

system has two modes. system $command will run $command in the shell.

# This will write 'foo' to the file 'bar'
system "echo foo > bar";

system @command 实际上是 system $program, @args.它将绕过 shell 并使用 @args 运行 $program.

system @command is really system $program, @args. It will bypass the shell and run the $program with @args.

# This will print 'foo > bar'
system "echo", "foo", ">", "bar"

所以如果你想像这样进行输出重定向，你可以将@command 连接在一起.

So if you want to do output redirection like that you could join @command together.

system join " ", @command;

但这可能会遇到 shell 引用问题.在 Perl 中使用 管道打开自己进行重定向更安全、更快、更便携.

But that can run into shell quoting issues. It's safer, faster, and more portable to do the redirection yourself in Perl using a piped open.

use strict;
use warnings;
use autodie;

open my $echo, "-|", "echo", "foo";
open my $log, ">", "some.log";

print {$log} <$echo>;

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