in reply to Re^2: Capture::Tiny alternative
in thread Capture::Tiny alternative

Hello again melezhik ,

Create and post some example where you will be testing your code so future visitors have a good starting point or ideas on how to implement it on their project(s).

Keep the "force" strong :D.

Seeking for Perl wisdom...on the process of learning...not there...yet!

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Re^4: Capture::Tiny alternative
by melezhik (Monk) on Mar 24, 2017 at 13:47 UTC

    Yeah, sure. when I get something to show I will put it here.

    Meanwhile here is example of how simple script using Perl IPC to read from external program may hangs : 

    
$ cat test.pl

my $cmd = '/usr/sbin/sshuttle -v -D -r  vagrant@127.0.0.1 192.168.0.0/24';

open(OUT, "$cmd 2>&1 |") || die "can't fork: $!";

while (my $l = <OUT>) {
  print $l;
}

    When I run test.pl it hangs: 

    $ perl test.pl
Starting sshuttle proxy.
Listening on ('127.0.0.1', 12300).
c : connecting to server...
vagrant@127.0.0.1's password:
c : connected.
Connected.

...

^C # I have to enter control C to finish my script

    When run the same command directly, it does not hang: 

    
$ /usr/sbin/sshuttle -v -D -r  vagrant@127.0.0.1 192.168.0.0/24
Starting sshuttle proxy.
Listening on ('127.0.0.1', 12300).
c : connecting to server...
vagrant@127.0.0.1's password:
c : connected.
Connected.
$ # finishes without interruption ..

    Sshutle information could be found here - https://github.com/apenwarr/sshuttle
    But I provide it only __as example__. Probably other command will cause the same Perl/IPC behavior. Any ideas why?


    And yeah , with Capture::Tiny sshutle does not hang ...
[reply]

      Hello again melezhik ,

      Try your command like this:

      my $cmd = `/usr/sbin/sshuttle -v -D -r  vagrant@127.0.0.1 192.168.0.0/
+24`;

      [download]

      Instead of this:

      my $cmd = '/usr/sbin/sshuttle -v -D -r  vagrant@127.0.0.1 192.168.0.0/
+24';

      [download]

      Read more about it here (How to run a shell script from a Perl program?).

      Seeking for Perl wisdom...on the process of learning...not there...yet!
[reply]
[d/l]
[select]
        my $cmd = `/usr/sbin/sshuttle ...` Instead of this: my $cmd = '/usr/sbin/sshuttle ...'

        I don't think that'll help, as the OP said they want to stream the output of the command, while backticks wait until the external command has completed.

        I suspect there's something going on in the IPC interaction between sshuttle and perl calling it (maybe sshuttle isn't daemonizing properly when called from Perl or something), at the moment I don't know more.

        melezhik: Just a guess, try my $cmd = 'nohup /usr/sbin/sshuttle ...' although that may prevent you from capturing its output, not sure if that's what you want or not. But since you're asking sshuttle to damonize (-D) anyways...

[reply]
[d/l]
[select]
        Anyway, Capture::Tiny::Extended looks like good for me, so I will try ... and let know ...
[reply]
        yeah, but this way does not work if I want real time STDOUT/STDEER reading ...
[reply]

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