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Manual Reference Pages  -  NET::OPENSSH::OSTRACER (3)

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Net::OpenSSH::OSTracer - trace ssh master process at the OS level



    use Net::OpenSSH;
    $Net::OpenSSH::debug |= 512;

    Net::OpenSSH->new($host)->system("echo hello world");

    system "less /tmp/net_openssh_master.*.strace";


This is a Net::OpenSSH helper module that allows you to trace the master ssh process at the operating system level using the proper utility available in your system (e.g., strace, truss, ktruss, tusc, etc.).

This feature can be used when debugging your programs or to report bugs on the module.

It is enabled setting the flag 512 on the $Net::OpenSSH::debug variable:

  $Net::OpenSSH::debug |= 512;

By default the output files of the tracer are saved as /tmp/net_openssh_master.$pid.$tracer_type.

Also, the output send by the tracer to stdout/stderr is saved as /tmp/net_openssh_master.$pid.txt.

The module can be configured through the following global variables:
$Net::OpenSSH::OSTracer::type By default, the module decides which tracer to use in base to the operating system name. This variable allows one to select a different tracer.

Currently accepted types are: strace (Linux), ktrace (*BSD), tusc (HP-UX) and truss (Solaris and AIX).

$Net::OpenSSH::OSTracer::cmd Command to execute for tracing the ssh process.

By default, it infers it from the tracer type selected.

$Net::OpenSSH::OSTracer::output Basename for the destination file. The PID of the ssh process and the tracer type will be appended.
$Net::OpenSSH::OSTracer::sudo This variable can be used to request the tracer to be run with sudo (some operating systems as for example Ubuntu, do not allow one to attach tracers, even to your own processes, unless you do it as root).

The variable has to be set with the path of the sudo binary. For instance:

  $Net::OpenSSH::OSTracer::sudo = /usr/bin/sudo;

If you need to pass a password to sudo, set the environment variable SUDO_ASKPASS. For instance:


$Net::OpenSSH::OSTracer::delay This variable can be used to delay the ssh execution so that the tracer can attach the process first. This is specially handy when using sudo with a password.


This module has not been tested under all the operating systems is says to support.

If you find any problem, just report it, please!


Copyright (C) 2012 by Salvador Fandinõ (

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.10.0 or, at your option, any later version of Perl 5 you may have available.

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perl v5.20.3 NET::OPENSSH::OSTRACER (3) 2015-10-12

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