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I thought this must be simple, but I haven't found a viable solution.

The problem is as simple as this: I want to execute a system command and capture the output in Perl variable. The command is specified in Perl array (containing command and parameters, e.g. @cmd = ('mycmd', '-opt1', 'arg1', 'val1')).

I don't want to use forking, i.e. open(FROM_KID, '-|') is not an option. I know that if I had the command in a string I can achieve this with backticks. So perhaps this problem reduces to converting @cmd array into a string. In my case, the command arguments can contain spaces.

Is there a simple way to convert @cmd array into string that can be used with backticks, but such that all arguments are properly quoted? Also ideally without using any external libraries.

Thanks!!

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    First, using system or backtics will fork a child process - there's no way around that. You could do something like $cmd = join(' ', map { s/'/\\'/g; "'$_'" } @cmd); but open would probably be safer.. Commented Sep 16, 2015 at 17:42
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    Re "I don't want to use forking", It's impossible not to fork. That's how all processes are created in unix, including when using system. Commented Sep 16, 2015 at 17:46
  • By forking, I meant implicit forking the Perl process itself that opening a pipe does, as I understood. Commented Sep 16, 2015 at 18:04
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    That's the same as the implicit forking done by system and backticks. Commented Sep 16, 2015 at 18:20
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    You should explain why you think you don't want to fork a subprocess, and why you don't want to use a Perl module Commented Sep 16, 2015 at 21:39

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You may be looking for String::ShellQuote. Note that only Bourne shell quoting is supported.

But backticks also perform an implicit fork, and if they in any way differ from the implicit fork of pipe open, I for one never noticed. :-\

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The String::ShellQuote is third-party package, which I would like to avoid. We have an existing script that uses only core packages and supports Perl back to version 5.8. I just need to make it work under Windows with possibly not affecting the minimum requirements or adding dependency on packages not in core.
String::ShellQuote is pure Perl – you could copy the code from it. But it will only work with Bourne shell, not with Windows' command.exe/cmd.exe. On Windows, you'd need Win32::ShellQuote – or a recent enough version of perl that pipe open works. ;-)
The Win32::ShellQuote seems to be a place to borrow the code from. Thanks!

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