1Net::OpenSSH(3) User Contributed Perl Documentation Net::OpenSSH(3)
2
6 Net::OpenSSH - Perl SSH client package implemented on top of OpenSSH
7
9 use Net::OpenSSH;
10 my $ssh = Net::OpenSSH->new($host);
12 $ssh->error and
13 die "Couldn't establish SSH connection: ". $ssh->error;
14 $ssh->system("ls /tmp") or
16 die "remote command failed: " . $ssh->error;
17 my @ls = $ssh->capture("ls");
19 $ssh->error and
20 die "remote ls command failed: " . $ssh->error;
21 my ($out, $err) = $ssh->capture2("find /root");
23 $ssh->error and
24 die "remote find command failed: " . $ssh->error;
25 my ($rin, $pid) = $ssh->pipe_in("cat >/tmp/foo") or
27 die "pipe_in method failed: " . $ssh->error;
28 print $rin "hello\n";
30 close $rin;
31 my ($rout, $pid) = $ssh->pipe_out("cat /tmp/foo") or
33 die "pipe_out method failed: " . $ssh->error;
34 while (<$rout>) { print }
36 close $rout;
37 my ($in, $out ,$pid) = $ssh->open2("foo");
39 my ($pty, $pid) = $ssh->open2pty("foo");
40 my ($in, $out, $err, $pid) = $ssh->open3("foo");
41 my ($pty, $err, $pid) = $ssh->open3pty("login");
42 my $sftp = $ssh->sftp();
44 $sftp->error and die "SFTP failed: " . $sftp->error;
45
47 Net::OpenSSH is a secure shell client package implemented on top of
48 OpenSSH binary client ("ssh").
49 Under the hood
51 This package is implemented around the multiplexing feature found in
52 later versions of OpenSSH. That feature allows one to run several
53 sessions over a single SSH connection (OpenSSH 4.1 was the first one to
54 provide all the required functionality).
55 When a new Net::OpenSSH object is created, the OpenSSH "ssh" client is
57 run in master mode, establishing a persistent (for the lifetime of the
58 object) connection to the server.
59 Then, every time a new operation is requested a new "ssh" process is
61 started in slave mode, effectively reusing the master SSH connection to
62 send the request to the remote side.
63 Net::OpenSSH Vs. Net::SSH::.* modules
65 Why should you use Net::OpenSSH instead of any of the other Perl SSH
66 clients available?
67 Well, this is my (biased) opinion:
69 Net::SSH::Perl is not well maintained nowadays (update: a new
71 maintainer has stepped in so this situation could change!!!), requires
72 a bunch of modules (some of them very difficult to install) to be
73 acceptably efficient and has an API that is limited in some ways.
74 Net::SSH2 is much better than Net::SSH::Perl, but not completely stable
76 yet. It can be very difficult to install on some specific operating
77 systems and its API is also limited, in the same way as Net::SSH::Perl.
78 Using Net::SSH::Expect, in general, is a bad idea. Handling interaction
80 with a shell via Expect in a generic way just can not be reliably done.
81 Net::SSH is just a wrapper around any SSH binary commands available on
83 the machine. It can be very slow as they establish a new SSH connection
84 for every operation performed.
85 In comparison, Net::OpenSSH is a pure perl module that does not have
87 any mandatory dependencies (obviously, besides requiring OpenSSH
88 binaries).
89 Net::OpenSSH has a very perlish interface. Most operations are
91 performed in a fashion very similar to that of the Perl builtins and
92 common modules (e.g. IPC::Open2).
93 It is also very fast. The overhead introduced by launching a new ssh
95 process for every operation is not appreciable (at least on my Linux
96 box). The bottleneck is the latency intrinsic to the protocol, so
97 Net::OpenSSH is probably as fast as an SSH client can be.
98 Being based on OpenSSH is also an advantage: a proved, stable, secure
100 (to paranoid levels), inseparably and well maintained implementation of
101 the SSH protocol is used.
102 On the other hand, Net::OpenSSH does not work on Windows, not even
104 under Cygwin.
105 Net::OpenSSH specifically requires the OpenSSH SSH client (AFAIK, the
107 multiplexing feature is not available from any other SSH client).
108 However, note that it will interact with any server software, not just
109 servers running OpenSSH "sshd".
110 For password authentication, IO::Pty has to be installed. Other modules
112 and binaries are also required to implement specific functionality (for
113 instance Net::SFTP::Foreign, Expect or rsync(1)).
114 Net::OpenSSH and Net::SSH2 do not support version 1 of the SSH
116 protocol.
117
119 Optional arguments
120 Almost all methods in this package accept as first argument an optional
121 reference to a hash containing parameters ("\%opts"). For instance,
122 these two method calls are equivalent:
123 my $out1 = $ssh->capture(@cmd);
125 my $out2 = $ssh->capture({}, @cmd);
126 Error handling
128 Most methods return undef (or an empty list) to indicate failure.
129 The "error" method can always be used to explicitly check for errors.
131 For instance:
132 my ($output, $errput) = $ssh->capture2({timeout => 1}, "find /");
134 $ssh->error and die "ssh failed: " . $ssh->error;
135 Net::OpenSSH methods
137 These are the methods provided by the package:
138 Net::OpenSSH->new($host, %opts)
140 Creates a new SSH master connection
141 $host can be a hostname or an IP address. It may also contain the
143 name of the user, her password and the TCP port number where the
144 server is listening:
145 my $ssh1 = Net::OpenSSH->new('jack@foo.bar.com');
147 my $ssh2 = Net::OpenSSH->new('jack:secret@foo.bar.com:10022');
148 my $ssh3 = Net::OpenSSH->new('jsmith@2001:db8::1428:57ab'); # IPv6
149 IPv6 addresses may optionally be enclosed in brackets:
151 my $ssh4 = Net::OpenSSH->new('jsmith@[::1]:1022');
153 This method always succeeds in returning a new object. Error
155 checking has to be performed explicitly afterwards:
156 my $ssh = Net::OpenSSH->new($host, %opts);
158 $ssh->error and die "Can't ssh to $host: " . $ssh->error;
159 If you have problems getting Net::OpenSSH to connect to the remote
161 host read the troubleshooting chapter near the end of this
162 document.
163 Accepted options:
165 user => $user_name
167 Login name
168 port => $port
170 TCP port number where the server is running
171 password => $password
173 User given password for authentication.
174 Note that using password authentication in automated scripts is
176 a very bad idea. When possible, you should use public key
177 authentication instead.
178 passphrase => $passphrase
180 Uses given passphrase to open private key.
181 key_path => $private_key_path
183 Uses the key stored on the given file path for authentication.
184 gateway => $gateway
186 If the given argument is a gateway object as returned by
187 "find_gateway" in Net::OpenSSH::Gateway method, use it to
188 connect to the remote host.
189 If it is a hash reference, call the "find_gateway" method
191 first.
192 For instance, the following code fragments are equivalent:
194 my $gateway = Net::OpenSSH::Gateway->find_gateway(
196 proxy => 'http://proxy.corporate.com');
197 $ssh = Net::OpenSSH->new($host, gateway => $gateway);
198 and
200 $ssh = Net::OpenSSH->new($host,
202 gateway => { proxy => 'http://proxy.corporate.com'});
203 proxy_command => $proxy_command
205 Use the given command to establish the connection to the remote
206 host (see "ProxyCommand" on ssh_config(5)).
207 batch_mode => 1
209 Disables querying the user for password and passphrases.
210 ctl_dir => $path
212 Directory where the SSH master control socket will be created.
213 This directory and its parents must be writable only by the
215 current effective user or root, otherwise the connection will
216 be aborted to avoid insecure operation.
217 By default "~/.libnet-openssh-perl" is used.
219 ctl_path => $path
221 Path to the SSH master control socket.
222 Usually this option should be avoided as the module is able to
224 pick an unused socket path by itself. An exception to that rule
225 is when the "external_master" feature is enabled.
226 Note that the length of the path is usually limited to between
228 92 and 108 bytes, depending of the underlying operating system.
229 ssh_cmd => $cmd
231 Name or full path to OpenSSH "ssh" binary. For instance:
232 my $ssh = Net::OpenSSH->new($host, ssh_cmd => '/opt/OpenSSH/bin/ssh');
234 scp_cmd => $cmd
236 Name or full path to OpenSSH "scp" binary.
237 By default it is inferred from the "ssh" one.
239 rsync_cmd => $cmd
241 Name or full path to "rsync" binary. Defaults to "rsync".
242 remote_shell => $name
244 Name of the remote shell. Used to select the argument quoter
245 backend.
246 timeout => $timeout
248 Maximum acceptable time that can elapse without network traffic
249 or any other event happening on methods that are not immediate
250 (for instance, when establishing the master SSH connection or
251 inside methods "capture", "system", "scp_get", etc.).
252 See also "Timeouts".
254 kill_ssh_on_timeout => 1
256 This option tells Net::OpenSSH to kill the local slave SSH
257 process when some operation times out.
258 See also "Timeouts".
260 strict_mode => 0
262 By default, the connection will be aborted if the path to the
263 socket used for multiplexing is found to be non-secure (for
264 instance, when any of the parent directories is writable by
265 other users).
266 This option can be used to disable that feature. Use with
268 care!!!
269 async => 1
271 By default, the constructor waits until the multiplexing socket
272 is available. That option can be used to defer the waiting
273 until the socket is actually used.
274 For instance, the following code connects to several remote
276 machines in parallel:
277 my (%ssh, %ls);
279 # multiple connections are established in parallel:
280 for my $host (@hosts) {
281 $ssh{$host} = Net::OpenSSH->new($host, async => 1);
282 }
283 # then to run some command in all the hosts (sequentially):
284 for my $host (@hosts) {
285 $ssh{$host}->system('ls /');
286 }
287 connect => 0
289 Do not launch the master SSH process yet.
290 master_opts => [...]
292 Additional options to pass to the "ssh" command when
293 establishing the master connection. For instance:
294 my $ssh = Net::OpenSSH->new($host,
296 master_opts => [-o => "ProxyCommand corkscrew httpproxy 8080 $host"]);
297 default_ssh_opts => [...]
299 Default slave SSH command line options for "open_ex" and
300 derived methods.
301 For instance:
303 my $ssh = Net::OpenSSH->new($host,
305 default_ssh_opts => [-o => "ConnectionAttempts=0"]);
306 forward_agent => 1
308 forward_agent => 'always'
309 Enables forwarding of the authentication agent.
310 When "always" is passed as the argument, agent forwarding will
312 be enabled by default in all the channels created from the
313 object. Otherwise, it will have to be explicitly requested when
314 calling the channel creating methods (i.e. "open_ex" and its
315 derivations).
316 This option can not be used when passing a passphrase (via
318 "passphrase") to unlock the login private key.
319 Note that Net::OpenSSH will not run "ssh-agent" for you. This
321 has to be done ahead of time and the environment variable
322 "SSH_AUTH_SOCK" set pointing to the proper place.
323 forward_X11 => 1
325 Enables forwarding of the X11 protocol
326 default_stdin_fh => $fh
328 default_stdout_fh => $fh
329 default_stderr_fh => $fh
330 Default I/O streams for "open_ex" and derived methods
331 (currently, that means any method but "pipe_in" and "pipe_out"
332 and I plan to remove those exceptions soon!).
333 For instance:
335 open my $stderr_fh, '>>', '/tmp/$host.err' or die ...;
337 open my $stdout_fh, '>>', '/tmp/$host.log' or die ...;
338 my $ssh = Net::OpenSSH->new($host, default_stderr_fh => $stderr_fh,
340 default_stdout_fh => $stdout_fh);
341 $ssh->error and die "SSH connection failed: " . $ssh->error;
342 $ssh->scp_put("/foo/bar*", "/tmp")
344 or die "scp failed: " . $ssh->error;
345 default_stdin_file = $fn
347 default_stdout_file = $fn
348 default_stderr_file = $fn
349 Opens the given file names and use them as the defaults.
350 master_stdout_fh => $fh
352 master_stderr_fh => $fh
353 Redirect corresponding stdio streams of the master SSH process
354 to given filehandles.
355 master_stdout_discard => $bool
357 master_stderr_discard => $bool
358 Discard corresponding stdio streams.
359 expand_vars => $bool
361 Activates variable expansion inside command arguments and file
362 paths.
363 See "Variable expansion" below.
365 vars => \%vars
367 Initial set of variables.
368 external_master => 1
370 Instead of launching a new OpenSSH client in master mode, the
371 module tries to reuse an already existent one. "ctl_path" must
372 also be passed when this option is set. See also
373 "get_ctl_path".
374 Example:
376 $ssh = Net::OpenSSH->new('foo', external_master => 1, ctl_path = $path);
378 When "external_master" is set, the hostname argument becomes
380 optional (0.0.0.0 is passed to OpenSSH which does not use it at
381 all).
382 default_encoding => $encoding
384 default_stream_encoding => $encoding
385 default_argument_encoding => $encoding
386 Set default encodings. See "Data encoding".
387 password_prompt => $string
389 password_prompt => $re
390 By default, when using password authentication, the module
391 expects the remote side to send a password prompt matching
392 "/[?:]/".
393 This option can be used to override that default for the rare
395 cases when a different prompt is used.
396 Examples:
398 password_prompt => ']'; # no need to escape ']'
400 password_prompt => qr/[:?>]/;
401 login_handler => \&custom_login_handler
403 Some remote SSH server may require a custom
404 login/authentication interaction not natively supported by
405 Net::OpenSSH. In that cases, you can use this option to replace
406 the default login logic.
407 The callback will be invoked repeatedly as
409 "custom_login_handler($ssh, $pty, $data)" where $ssh is the
410 current Net::OpenSSH object, "pty" a IO::Pty object attached to
411 the slave "ssh" process tty and $data a reference to an scalar
412 you can use at will.
413 The login handler must return 1 after the login process has
415 completed successfully or 0 in case it still needs to do
416 something else. If some error happens, it must die.
417 Note, that blocking operations should not be performed inside
419 the login handler (at least if you want the "async" and
420 "timeout" features to work).
421 See also the sample script "login_handler.pl" in the "examples"
423 directory.
424 Usage of this option is incompatible with the "password" and
426 "passphrase" options, you will have to handle password or
427 passphrases from the custom handler yourself.
428 master_setpgrp => 1
430 When this option is set, the master process is run as a
431 different process group. As a consequence it will not die when
432 the user presses Ctrl-C at the terminal.
433 In order to allow the master SSH process to request any
435 information from the user, the module may set it as the
436 terminal controlling process while the connection is
437 established (using "tcsetpgrp" in POSIX). Afterwards, the
438 terminal controlling process is reset.
439 This feature is highly experimental. Report any problems you
441 may find, please.
442 master_pty_force => 1
444 By default, Net::OpenSSH attaches the master SSH process to a
445 pty only when some kind of interactive authentication is
446 requested. If this flag is set a pty will be attached always.
447 That allows to get better diagnostics for some kind of errors
449 (as for instance, bad host keys) and also allows to retrieve
450 the pty log using get_master_pty_log.
451 $ssh->error
453 Returns the error condition for the last performed operation.
454 The returned value is a dualvar as $! (see "$!" in perlvar) that
456 renders an informative message when used in string context or an
457 error number in numeric context (error codes appear in
458 Net::OpenSSH::Constants).
459 $ssh->get_master_pty_log
461 In order to handle password authentication or entering the
462 passphrase for a private key, Net::OpenSSH may run the master SSH
463 process attached to a pty.
464 In that case and after a constructor call returns a connection
466 failure error, this method can be called to retrieve the output
467 captured at the pty (the log is discarded when the connection is
468 established successfully).
469 Any data consumed from the pty by custom login handlers will be
471 missing from the the returned log.
472 $ssh->get_user
474 $ssh->get_host
475 $ssh->get_port
476 Return the corresponding SSH login parameters.
477 $ssh->get_ctl_path
479 Returns the path to the socket where the OpenSSH master process
480 listens for new multiplexed connections.
481 ($in, $out, $err, $pid) = $ssh->open_ex(\%opts, @cmd)
483 Note: this is a low level method which, probably, you do not need
484 to use!
485 That method starts the command @cmd on the remote machine creating
487 new pipes for the IO channels as specified on the %opts hash.
488 If @cmd is omitted, the remote user shell is run.
490 Returns four values, the first three ($in, $out and $err)
492 correspond to the local side of the pipes created (they can be
493 undef) and the fourth ($pid) to the PID of the new SSH slave
494 process. An empty list is returned on failure.
495 Note that "waitpid" has to be used afterwards to reap the slave SSH
497 process.
498 Accepted options:
500 stdin_pipe => 1
502 Creates a new pipe and connects the reading side to the stdin
503 stream of the remote process. The writing side is returned as
504 the first value ($in).
505 stdin_pty => 1
507 Similar to "stdin_pipe", but instead of a regular pipe it uses
508 a pseudo-tty (pty).
509 Note that on some operating systems (e.g. HP-UX, AIX), ttys are
511 not reliable. They can overflow when large chunks are written
512 or when data is written faster than it is read.
513 stdin_fh => $fh
515 Duplicates $fh and uses it as the stdin stream of the remote
516 process.
517 stdin_file => $filename
519 stdin_file => \@open_args
520 Opens the file of the given name for reading and uses it as the
521 remote process stdin stream.
522 If an array reference is passed its contents are used as the
524 arguments for the underlying open call. For instance:
525 $ssh->system({stdin_file => ['-|', 'gzip -c -d file.gz']}, $rcmd);
527 stdin_discard => 1
529 Uses /dev/null as the remote process stdin stream.
530 stdout_pipe => 1
532 Creates a new pipe and connects the writing side to the stdout
533 stream of the remote process. The reading side is returned as
534 the second value ($out).
535 stdout_pty => 1
537 Connects the stdout stream of the remote process to the pseudo-
538 pty. This option requires "stdin_pty" to be also set.
539 stdout_fh => $fh
541 Duplicates $fh and uses it as the stdout stream of the remote
542 process.
543 stdout_file => $filename
545 stdout_file => \@open_args
546 Opens the file of the given filename and redirect stdout there.
547 stdout_discard => 1
549 Uses /dev/null as the remote process stdout stream.
550 stdinout_socket => 1
552 Creates a new socketpair, attaches the stdin an stdout streams
553 of the slave SSH process to one end and returns the other as
554 the first value ($in) and undef for the second ($out).
555 Example:
557 my ($socket, undef, undef, $pid) = $ssh->open_ex({stdinout_socket => 1},
559 '/bin/netcat $dest');
560 See also "open2socket".
562 stdinout_dpipe => $cmd
564 stdinout_dpipe => \@cmd
565 Runs the given command locally attaching its stdio streams to
566 those of the remote SSH command. Conceptually it is equivalent
567 to the dpipe(1) shell command.
568 stderr_pipe => 1
570 Creates a new pipe and connects the writing side to the stderr
571 stream of the remote process. The reading side is returned as
572 the third value ($err).
573 Example:
575 my $pid = $ssh->open_ex({stdinout_dpipe => 'vncviewer -stdio'},
577 x11vnc => '-inetd');
578 stderr_fh => $fh
580 Duplicates $fh and uses it as the stderr stream of the remote
581 process.
582 stderr_file => $filename
584 Opens the file of the given name and redirects stderr there.
585 stderr_to_stdout => 1
587 Makes stderr point to stdout.
588 tty => $bool
590 Tells "ssh" to allocate a pseudo-tty for the remote process. By
591 default, a tty is allocated if remote command stdin stream is
592 attached to a tty.
593 When this flag is set and stdin is not attached to a tty, the
595 ssh master and slave processes may generate spurious warnings
596 about failed tty operations. This is caused by a bug present in
597 older versions of OpenSSH.
598 close_slave_pty => 0
600 When a pseudo pty is used for the stdin stream, the slave side
601 is automatically closed on the parent process after forking the
602 ssh command.
603 This option disables that feature, so that the slave pty can be
605 accessed on the parent process as "$pty->slave". It will have
606 to be explicitly closed (see IO::Pty)
607 quote_args => $bool
609 See "Shell quoting" below.
610 remote_shell => $shell
612 Sets the remote shell. Allows one to change the argument
613 quoting mechanism in a per-command fashion.
614 This may be useful when interacting with a Windows machine
616 where argument parsing may be done at the command level in
617 custom ways.
618 Example:
620 $ssh->system({remote_shell => 'MSWin'}, echo => $line);
622 $ssh->system({remote_shell => 'MSCmd,MSWin'}, type => $file);
623 forward_agent => $bool
625 Enables/disables forwarding of the authentication agent.
626 This option can only be used when agent forwarding has been
628 previously requested on the constructor.
629 forward_X11 => $bool
631 Enables/disables forwarding of the X11 protocol.
632 This option can only be used when X11 forwarding has been
634 previously requested on the constructor.
635 ssh_opts => \@opts
637 List of extra options for the "ssh" command.
638 This feature should be used with care, as the given options are
640 not checked in any way by the module, and they could interfere
641 with it.
642 tunnel => $bool
644 Instead of executing a command in the remote host, this option
645 instruct Net::OpenSSH to create a TCP tunnel. The arguments
646 become the target IP and port or the remote path for an Unix
647 socket.
648 Example:
650 my ($in, $out, undef, $pid) = $ssh->open_ex({tunnel => 1}, $IP, $port);
652 my ($in, $out, undef, $pid) = $ssh->open_ex({tunnel => 1}, $socket_path);
653 See also "Tunnels".
655 subsystem => $bool
657 Request a connection to a SSH subsystem. The name of the
658 subsystem must be passed as an argument, as in the following
659 example:
660 my $s = $ssh->open2socket({subsystem => 1}, 'netconf');
662 encoding => $encoding
664 argument_encoding => $encoding
665 Set encodings. See "Data encoding".
666 Usage example:
668 # similar to IPC::Open2 open2 function:
670 my ($in_pipe, $out_pipe, undef, $pid) =
671 $ssh->open_ex( { stdin_pipe => 1,
672 stdout_pipe => 1 },
673 @cmd )
674 or die "open_ex failed: " . $ssh->error;
675 # do some IO through $in/$out
676 # ...
677 waitpid($pid);
678 setpgrp => 1
680 Calls "setpgrp" after forking the child process. As a result it
681 will not die when the user presses Ctrl+C at the console. See also
682 "setpgrp" in perlfunc.
683 Using this option without also setting "master_setpgrp" on the
685 constructor call is mostly useless as the signal will be delivered
686 to the master process and all the remote commands aborted.
687 This feature is experimental.
689 $ssh->system(\%opts, @cmd)
691 Runs the command @cmd on the remote machine.
692 Returns true on success, undef otherwise.
694 The error status is set to "OSSH_SLAVE_CMD_FAILED" when the remote
696 command exits with a non zero code (the code is available from $?,
697 see "$?" in perlvar).
698 Example:
700 $ssh->system('ls -R /')
702 or die "ls failed: " . $ssh->error";
703 As for "system" builtin, "SIGINT" and "SIGQUIT" signals are
705 blocked. (see "system" in perlfunc). Also, setting $SIG{CHLD} to
706 "IGNORE" or to a custom signal handler will interfere with this
707 method.
708 Accepted options:
710 stdin_data => $input
712 stdin_data => \@input
713 Sends the given data through the stdin stream to the remote
714 process.
715 For example, the following code creates a file on the remote
717 side:
718 $ssh->system({stdin_data => \@data}, "cat >/tmp/foo")
720 or die "unable to write file: " . $ssh->error;
721 timeout => $timeout
723 The operation is aborted after $timeout seconds elapsed without
724 network activity.
725 See also "Timeouts".
727 async => 1
729 Does not wait for the child process to exit. The PID of the new
730 process is returned.
731 Note that when this option is combined with "stdin_data", the
733 given data will be transferred to the remote side before
734 returning control to the caller.
735 See also the "spawn" method documentation below.
737 stdin_fh => $fh
739 stdin_discard => $bool
740 stdout_fh => $fh
741 stdout_discard => $bool
742 stderr_fh => $fh
743 stderr_discard => $bool
744 stderr_to_stdout => $bool
745 stdinout_dpipe => $cmd
746 tty => $bool
747 See the "open_ex" method documentation for an explanation of
748 these options.
749 stdin_keep_open => $bool
751 When "stdin_data" is given, the module closes the stdin stream
752 once all the data has been sent. Unfortunately, some SSH buggy
753 servers fail to handle this event correctly and close the
754 channel prematurely.
755 As a workaround, when this flag is set the stdin is left open
757 until the remote process terminates.
758 $ok = $ssh->test(\%opts, @cmd);
760 Runs the given command and returns its success/failure exit status
761 as 1 or 0 respectively. Returns undef when something goes wrong in
762 the SSH layer.
763 Error status is not set to OSSH_SLAVE_CMD_FAILED when the remote
765 command exits with a non-zero code.
766 By default this method discards the remote command "stdout" and
768 "sterr" streams.
769 Usage example:
771 if ($ssh->test(ps => -C => $executable)) {
773 say "$executable is running on remote machine"
774 }
775 else {
776 die "something got wrong: ". $ssh->error if $ssh->error;
777 say "$executable is not running on remote machine"
779 }
780 This method support the same set of options as "system", except
782 "async" and "tunnel".
783 $output = $ssh->capture(\%opts, @cmd);
785 @output = $ssh->capture(\%opts, @cmd);
786 This method is conceptually equivalent to the perl backquote
787 operator (e.g. `ls`): it runs the command on the remote machine and
788 captures its output.
789 In scalar context returns the output as a scalar. In list context
791 returns the output broken into lines (it honors $/, see "$/" in
792 perlvar).
793 The exit status of the remote command is returned in $?.
795 When an error happens while capturing (for instance, the operation
797 times out), the partial captured output will be returned. Error
798 conditions have to be explicitly checked using the "error" method.
799 For instance:
800 my $output = $ssh->capture({ timeout => 10 },
802 "echo hello; sleep 20; echo bye");
803 $ssh->error and
804 warn "operation didn't complete successfully: ". $ssh->error;
805 print $output;
806 Setting $SIG{CHLD} to a custom signal handler or to "IGNORE" will
808 interfere with this method.
809 Accepted options:
811 stdin_data => $input
813 stdin_data => \@input
814 stdin_keep_open => $bool
815 See the "system" method documentation for an explanation of
816 these options.
817 timeout => $timeout
819 See "Timeouts".
820 stdin_fh => $fh
822 stdin_discard => $bool
823 stderr_fh => $fh
824 stderr_discard => $bool
825 stderr_to_stdout => $bool
826 tty => $bool
827 See the "open_ex" method documentation for an explanation of
828 these options.
829 ($output, $errput) = $ssh->capture2(\%opts, @cmd)
831 captures the output sent to both stdout and stderr by @cmd on the
832 remote machine.
833 Setting $SIG{CHLD} to a custom signal handler or to "IGNORE" will
835 also interfere with this method.
836 The accepted options are:
838 stdin_data => $input
840 stdin_data => \@input
841 stdin_keep_open => $bool
842 See the "system" method documentation for an explanation of
843 these options.
844 timeout => $timeout
846 See "Timeouts".
847 stdin_fh => $fh
849 stdin_discard => $bool
850 tty => $bool
851 See the "open_ex" method documentation for an explanation of
852 these options.
853 ($in, $pid) = $ssh->pipe_in(\%opts, @cmd)
855 This method is similar to the following Perl "open" call
856 $pid = open $in, '|-', @cmd
858 but running @cmd on the remote machine (see "open" in perlfunc).
860 No options are currently accepted.
862 There is no need to perform a waitpid on the returned PID as it
864 will be done automatically by perl when $in is closed.
865 Example:
867 my ($in, $pid) = $ssh->pipe_in('cat >/tmp/fpp')
869 or die "pipe_in failed: " . $ssh->error;
870 print $in $_ for @data;
871 close $in or die "close failed";
872 ($out, $pid) = $ssh->pipe_out(\%opts, @cmd)
874 Reciprocal to previous method, it is equivalent to
875 $pid = open $out, '-|', @cmd
877 running @cmd on the remote machine.
879 No options are currently accepted.
881 ($in, $out, $pid) = $ssh->open2(\%opts, @cmd)
883 ($pty, $pid) = $ssh->open2pty(\%opts, @cmd)
884 ($socket, $pid) = $ssh->open2socket(\%opts, @cmd)
885 ($in, $out, $err, $pid) = $ssh->open3(\%opts, @cmd)
886 ($pty, $err, $pid) = $ssh->open3pty(\%opts, @cmd)
887 Shortcuts around "open_ex" method.
888 $pid = $ssh->spawn(\%opts, @_)
890 Another "open_ex" shortcut, it launches a new remote process in the
891 background and returns the PID of the local slave SSH process.
892 At some later point in your script, "waitpid" should be called on
894 the returned PID in order to reap the slave SSH process.
895 For instance, you can run some command on several hosts in parallel
897 with the following code:
898 my %conn = map { $_ => Net::OpenSSH->new($_, async => 1) } @hosts;
900 my @pid;
901 for my $host (@hosts) {
902 open my($fh), '>', "/tmp/out-$host.txt"
903 or die "unable to create file: $!";
904 push @pid, $conn{$host}->spawn({stdout_fh => $fh}, $cmd);
905 }
906 waitpid($_, 0) for @pid;
908 Note that "spawn" should not be used to start detached remote
910 processes that may survive the local program (see also the "FAQ"
911 about running remote processes detached).
912 ($socket, $pid) = $ssh->open_tunnel(\%opts, $dest_host, $port)
914 ($socket, $pid) = $ssh->open_tunnel(\%opts, $socket_path)
915 Similar to "open2socket", but instead of running a command, it
916 opens a TCP tunnel to the given address. See also "Tunnels".
917 $out = $ssh->capture_tunnel(\%opts, $dest_host, $port)
919 @out = $ssh->capture_tunnel(\%opts, $dest_host, $port)
920 Similar to "capture", but instead of running a command, it opens a
921 TCP tunnel.
922 Example:
924 $out = $ssh->capture_tunnel({stdin_data => join("\r\n",
926 "GET / HTTP/1.0",
927 "Host: www.perl.org",
928 "", "") },
929 'www.perl.org', 80)
930 See also "Tunnels".
932 $ssh->scp_get(\%opts, $remote1, $remote2,..., $local_dir_or_file)
934 $ssh->scp_put(\%opts, $local, $local2,..., $remote_dir_or_file)
935 These two methods are wrappers around the "scp" command that allow
936 transfers of files to/from the remote host using the existing SSH
937 master connection.
938 When transferring several files, the target argument must point to
940 an existing directory. If only one file is to be transferred, the
941 target argument can be a directory or a file name or can be
942 omitted. For instance:
943 $ssh->scp_get({glob => 1}, '/var/tmp/foo*', '/var/tmp/bar*', '/tmp');
945 $ssh->scp_put('/etc/passwd');
946 Both "scp_get" and "scp_put" methods return a true value when all
948 the files are transferred correctly, otherwise they return undef.
949 Accepted options:
951 quiet => 0
953 By default, "scp" is called with the quiet flag "-q" enabled in
954 order to suppress progress information. This option allows one
955 to re-enable the progress indication bar.
956 verbose => 1
958 Calls "scp" with the "-v" flag.
959 recursive => 1
961 Copies files and directories recursively.
962 glob => 1
964 Enables expansion of shell metacharacters in the sources list
965 so that wildcards can be used to select files.
966 glob_flags => $flags
968 Second argument passed to File::Glob::bsd_glob function. Only
969 available for "scp_put" method.
970 copy_attrs => 1
972 Copies modification and access times and modes from the
973 original files.
974 bwlimit => $Kbits
976 Limits the used bandwidth, specified in Kbit/s.
977 timeout => $secs
979 The transfer is aborted if the connection does not finish
980 before the given timeout elapses. See also "Timeouts".
981 async => 1
983 Does not wait for the "scp" command to finish. When this option
984 is used, the method returns the PID of the child "scp" process.
985 For instance, it is possible to transfer files to several hosts
987 in parallel as follows:
988 use Errno;
990 my (%pid, %ssh);
991 for my $host (@hosts) {
992 $ssh{$host} = Net::OpenSSH->new($host, async => 1);
993 }
994 for my $host (@hosts) {
995 $pid{$host} = $ssh{$host}->scp_put({async => 1}, $local_fn, $remote_fn)
996 or warn "scp_put to $host failed: " . $ssh{$host}->error . "\n";
997 }
998 for my $host (@hosts) {
999 if (my $pid = $pid{$host}) {
1000 if (waitpid($pid, 0) > 0) {
1001 my $exit = ($? >> 8);
1002 $exit and warn "transfer of file to $host failed ($exit)\n";
1003 }
1004 else {
1005 redo if ($! == EINTR);
1006 warn "waitpid($pid) failed: $!\n";
1007 }
1008 }
1009 }
1010 stdout_fh => $fh
1012 stderr_fh => $fh
1013 stderr_to_stdout => 1
1014 These options are passed unchanged to method "open_ex",
1015 allowing capture of the output of the "scp" program.
1016 Note that "scp" will not generate progress reports unless its
1018 stdout stream is attached to a tty.
1019 ssh_opts => \@opts
1021 List of extra options for the "ssh" command.
1022 This feature should be used with care, as the given options are
1024 not checked in any way by the module, and they could interfere
1025 with it.
1026 $ssh->rsync_get(\%opts, $remote1, $remote2,..., $local_dir_or_file)
1028 $ssh->rsync_put(\%opts, $local1, $local2,..., $remote_dir_or_file)
1029 These methods use "rsync" over SSH to transfer files from/to the
1030 remote machine.
1031 They accept the same set of options as the "scp" ones.
1033 Any unrecognized option will be passed as an argument to the
1035 "rsync" command (see rsync(1)). Underscores can be used instead of
1036 dashes in "rsync" option names.
1037 For instance:
1039 $ssh->rsync_get({exclude => '*~',
1041 verbose => 1,
1042 safe_links => 1},
1043 '/remote/dir', '/local/dir');
1044 $sftp = $ssh->sftp(%sftp_opts)
1046 Creates a new Net::SFTP::Foreign object for SFTP interaction that
1047 runs through the ssh master connection.
1048 @call = $ssh->make_remote_command(\%opts, @cmd)
1050 $call = $ssh->make_remote_command(\%opts, @cmd)
1051 This method returns the arguments required to execute a command on
1052 the remote machine via SSH. For instance:
1053 my @call = $ssh->make_remote_command(ls => "/var/log");
1055 system @call;
1056 In scalar context, returns the arguments quoted and joined into one
1058 string:
1059 my $remote = $ssh->make_remote_comand("cd /tmp/ && tar xf -");
1061 system "tar cf - . | $remote";
1062 The options accepted are as follows:
1064 tty => $bool
1066 Enables/disables allocation of a tty on the remote side.
1067 forward_agent => $bool
1069 Enables/disables forwarding of authentication agent.
1070 This option can only be used when agent forwarding has been
1072 previously requested on the constructor.
1073 tunnel => 1
1075 Return a command to create a connection to some TCP server
1076 reachable from the remote host. In that case the arguments are
1077 the destination address and port. For instance:
1078 $cmd = $ssh->make_remote_command({tunnel => 1}, $host, $port);
1080 subsystem => 1
1082 Return a command for invoking a SSH subsystem (i.e. SFTP or
1083 netconf). In that case the only argument is the subsystem name.
1084 $ssh->wait_for_master($async)
1086 When the connection has been established by calling the constructor
1087 with the "async" option, this call allows one to advance the
1088 process.
1089 If $async is true, it will perform any work that can be done
1091 immediately without waiting (for instance, entering the password or
1092 checking for the existence of the multiplexing socket) and then
1093 return. If a false value is given, it will finalize the connection
1094 process and wait until the multiplexing socket is available.
1095 It returns a true value after the connection has been successfully
1097 established. False is returned if the connection process fails or
1098 if it has not yet completed (then, the "error" method can be used
1099 to distinguish between both cases).
1100 From version 0.64 upwards, undef is returned when the master is
1102 still in an unstable state (login, killing, etc.) and 0 when it is
1103 in a stable state (running, stopped or gone).
1104 $ssh->check_master
1106 This method runs several checks to ensure that the master
1107 connection is still alive.
1108 $ssh->shell_quote(@args)
1110 Returns the list of arguments quoted so that they will be restored
1111 to their original form when parsed by the remote shell.
1112 In scalar context returns the list of arguments quoted and joined.
1114 Usually this task is done automatically by the module. See "Shell
1116 quoting" below.
1117 This method can also be used as a class method.
1119 Example:
1121 my $quoted_args = Net::OpenSSH->shell_quote(@args);
1123 system('ssh', '--', $host, $quoted_args);
1124 $ssh->shell_quote_glob(@args)
1126 This method is like the previous "shell_quote" but leaves wildcard
1127 characters unquoted.
1128 It can be used as a class method also.
1130 $ssh->set_expand_vars($bool)
1132 Enables/disables variable expansion feature (see "Variable
1133 expansion").
1134 $ssh->get_expand_vars
1136 Returns current state of variable expansion feature.
1137 $ssh->set_var($name, $value)
1139 $ssh->get_var($name, $value)
1140 These methods allow one to change and to retrieve the value of the
1141 given name.
1142 $ssh->get_master_pid
1144 Returns the PID of the master SSH process
1145 $ssh->master_exited
1147 This methods allows one to tell the module that the master process
1148 has exited when we get its PID from some external wait or waitpid
1149 call. For instance:
1150 my $ssh = Net::OpenSSH->new('foo', async => 1);
1152 # create new processes
1154 # ...
1155 # rip them...
1157 my $master_pid = $ssh->master_pid;
1158 while ((my $pid = wait) > 0) {
1159 if ($pid == $master_pid) {
1160 $ssh->master_exited;
1161 }
1162 }
1163 If your program rips the master process and this method is not
1165 called, the OS could reassign the PID to a new unrelated process
1166 and the module would try to kill it at object destruction time.
1167 $ssh->disconnect($async)
1169 Shuts down the SSH connection.
1170 Usually, you don't need to call this method explicitly, but just
1172 let the Net::OpenSSH object go out of scope.
1173 If "async" is true, it doesn't wait for the SSH connection to
1175 terminate. In that case, "wait_for_master" must be called
1176 repeatedly until the shutdown sequence terminates (See the
1177 "AnyEvent" integration section below).
1178 $ssh->restart($async)
1180 Restarts the SSH session closing any open connection and creating a
1181 new one. Any open channel would also be killed.
1182 Note that calling this method may request again the password or
1184 passphrase from the user.
1185 In asynchronous mode, this method requires the connection to be
1187 terminated before it gets called. Afterwards, "wait_for_master"
1188 should be called repeaptly until the new connection is stablished.
1189 For instance:
1190 my $async = 1;
1192 $ssh->disconnect($async);
1193 while (1) {
1194 defined $ssh->wait_for_master($async) # returns 0 when the
1195 # disconnect process
1196 # finishes
1197 and last;
1198 do_something_else();
1199 }
1200 $ssh->restart($async);
1201 while (1) {
1202 defined $ssh->wait_for_master($async)
1203 and last;
1204 do_something_else();
1205 }
1206 $pid = $ssh->sshfs_import(\%opts, $remote_fs, $local_mnt_point)
1208 $pid = $ssh->sshfs_export(\%opts, $local_fs, $remote_mnt_point)
1209 These methods use sshfs(1) to import or export a file system
1210 through the SSH connection.
1211 They return the $pid of the "sshfs" process or of the slave "ssh"
1213 process used to proxy it. Killing that process unmounts the file
1214 system, though, it may be probably better to use fusermount(1).
1215 The options accepted are as follows:
1217 ssh_opts => \@ssh_opts
1219 Options passed to the slave "ssh" process.
1220 sshfs_opts => \@sshfs_opts
1222 Options passed to the "sshfs" command. For instance, to mount
1223 the file system in read-only mode:
1224 my $pid = $ssh->sshfs_export({sshfs_opts => [-o => 'ro']},
1226 "/", "/mnt/foo");
1227 Note that this command requires a recent version of "sshfs" to work
1229 (at the time of writing, it requires the yet unreleased version
1230 available from the FUSE git repository!).
1231 See also the sshfs(1) man page and the "sshfs" and FUSE web sites
1233 at <https://github.com/libfuse/sshfs> and
1234 <https://github.com/libfuse/libfuse> respectively.
1235 $or = $ssh->object_remote(@args)
1237 Returns an Object::Remote::Connection instance running on top of
1238 the Net::OpenSSH connection.
1239 Example:
1241 my $or = $ssh->object_remote;
1243 my $hostname = Sys::Hostname->can::on($or, 'hostname');
1244 say $hostname->();
1245 See also Object::Remote.
1247 $any = $ssh->any(%opts)
1249 Wraps the current object inside a Net::SSH::Any one.
1250 Example:
1252 my $any = $ssh->any;
1254 my $content = $any->scp_get_content("my-file.txt");
1255 $pid = $ssh->disown_master
1257 Under normal operation Net::OpenSSH controls the life-time of the
1258 master "ssh" process and when the object is destroyed the master
1259 process and any connection running over it are terminated.
1260 In some (rare) cases, it is desirable to let the master process and
1262 all the running connections survive. Calling this method does just
1263 that, it tells Net::OpenSSH object that the master process is not
1264 its own anymore.
1265 The return value is the PID of the master process.
1267 Note also that disowning the master process does not affect the
1269 operation of the module in any other regard.
1270 For instance:
1272 # See examples/sshfs_mount.pl for a working program
1274 my $ssh = Net::OpenSSH->new($host);
1275 my $sshfs_pid = $ssh->sshfs_import("/home/foo", "my-remote-home");
1276 $ssh->disown_master;
1277 $ssh->stop; # tells the master to stop accepting requests
1278 exit(0);
1279 Shell quoting
1281 By default, when invoking remote commands, this module tries to mimic
1282 perl "system" builtin in regard to argument processing. Quoting
1283 "system" in perlfunc:
1284 Argument processing varies depending on the number of arguments. If
1286 there is more than one argument in LIST, or if LIST is an array with
1287 more than one value, starts the program given by the first element
1288 of the list with arguments given by the rest of the list. If there
1289 is only one scalar argument, the argument is checked for shell
1290 metacharacters, and if there are any, the entire argument is passed
1291 to the system's command shell for parsing (this is "/bin/sh -c" on
1292 Unix platforms, but varies on other platforms).
1293 Take for example Net::OpenSSH "system" method:
1295 $ssh->system("ls -l *");
1297 $ssh->system('ls', '-l', '/');
1298 The first call passes the argument unchanged to ssh and it is executed
1300 in the remote side through the shell which interprets metacharacters.
1301 The second call escapes any shell metacharacters so that, effectively,
1303 it is equivalent to calling the command directly and not through the
1304 shell.
1305 Under the hood, as the Secure Shell protocol does not provide for this
1307 mode of operation and always spawns a new shell where it runs the given
1308 command, Net::OpenSSH quotes any shell metacharacters in the command
1309 list.
1310 All the methods that invoke a remote command (system, open_ex, etc.)
1312 accept the option "quote_args" that allows one to force/disable shell
1313 quoting.
1314 For instance:
1316 $ssh->system({quote_args => 1}, "/path with spaces/bin/foo");
1318 will correctly handle the spaces in the program path.
1320 The shell quoting mechanism implements some extensions (for instance,
1322 performing redirections to /dev/null on the remote side) that can be
1323 disabled with the option "quote_args_extended":
1324 $ssh->system({ stderr_discard => 1,
1326 quote_args => 1, quote_args_extended => 0 },
1327 @cmd);
1328 The option "quote_args" can also be used to disable quoting when more
1330 than one argument is passed. For instance, to get some pattern expanded
1331 by the remote shell:
1332 $ssh->system({quote_args => 0}, 'ls', '-l', "/tmp/files_*.dat");
1334 The method "shell_quote" can be used to selectively quote some
1336 arguments and leave others untouched:
1337 $ssh->system({quote_args => 0},
1339 $ssh->shell_quote('ls', '-l'),
1340 "/tmp/files_*.dat");
1341 When the glob option is set in "scp" and "rsync" file transfer methods,
1343 an alternative quoting method which knows about file wildcards and
1344 passes them unquoted is used. The set of wildcards recognized currently
1345 is the one supported by bash(1).
1346 Another way to selectively use quote globing or fully disable quoting
1348 for some specific arguments is to pass them as scalar references or
1349 double scalar references respectively. In practice, that means
1350 prepending them with one or two backslashes. For instance:
1351 # quote the last argument for globing:
1353 $ssh->system('ls', '-l', \'/tmp/my files/filed_*dat');
1354 # append a redirection to the remote command
1356 $ssh->system('ls', '-lR', \\'>/tmp/ls-lR.txt');
1357 # expand remote shell variables and glob in the same command:
1359 $ssh->system('tar', 'czf', \\'$HOME/out.tgz', \'/var/log/server.*.log');
1360 As shell quoting is a tricky matter, I expect bugs to appear in this
1362 area. You can see how "ssh" is called, and the quoting used setting the
1363 following debug flag:
1364 $Net::OpenSSH::debug |= 16;
1366 By default, the module assumes the remote shell is some variant of a
1368 POSIX or Bourne shell ("bash", "dash", "ksh", etc.). If this is not the
1369 case, the construction option "remote_shell" can be used to select an
1370 alternative quoting mechanism.
1371 For instance:
1373 $ssh = Net::OpenSSH->new($host, remote_shell => 'csh');
1375 $ssh->system(echo => "hard\n to\n quote\n argument!");
1376 Currently there are quoters available for POSIX (Bourne) compatible
1378 shells, "csh" and the two Windows variants "MSWin" (for servers using
1379 Win32::CreateProcess, see Net::OpenSSH::ShellQuoter::MSWin) and "MSCmd"
1380 (for servers using "cmd.exe", see Net::OpenSSH::ShellQuoter::MSCmd).
1381 In any case, you can always do the quoting yourself and pass the quoted
1383 remote command as a single string:
1384 # for VMS
1386 $ssh->system('DIR/SIZE NFOO::USERS:[JSMITH.DOCS]*.TXT;0');
1387 Note that the current quoting mechanism does not handle possible
1389 aliases defined by the remote shell. In that case, to force execution
1390 of the command instead of the alias, the full path to the command must
1391 be used.
1392 Timeouts
1394 In order to stop remote processes when they timeout, the ideal approach
1395 would be to send them signals through the SSH connection as specified
1396 by the protocol standard.
1397 Unfortunately OpenSSH does not implement that feature so Net::OpenSSH
1399 has to use other imperfect approaches:
1400 • close slave I/O streams
1402 Closing the STDIN and STDOUT streams of the unresponsive remote
1404 process will effectively deliver a SIGPIPE when it tries to access
1405 any of them.
1406 Remote processes may not access STDIN or STDOUT and even then,
1408 Net::OpenSSH can only close these channels when it is capturing
1409 them, so this approach does not always work.
1410 • killing the local SSH slave process
1412 This action may leave the remote process running, creating a remote
1414 orphan so Net::OpenSSH does not use it unless the construction
1415 option "kill_ssh_on_timeout" is set.
1416 Luckily, future versions of OpenSSH will support signaling remote
1418 processes via the mux channel.
1419 Variable expansion
1421 The variable expansion feature allows one to define variables that are
1422 expanded automatically inside command arguments and file paths.
1423 This feature is disabled by default. It is intended to be used with
1425 Net::OpenSSH::Parallel and other similar modules.
1426 Variables are delimited by a pair of percent signs ("%"), for instance
1428 "%HOST%". Also, two consecutive percent signs are replaced by a single
1429 one.
1430 The special variables "HOST", "USER" and "PORT" are maintained
1432 internally by the module and take the obvious values.
1433 Variable expansion is performed before shell quoting (see "Shell
1435 quoting").
1436 Some usage example:
1438 my $ssh = Net::OpenSSH->new('server.foo.com', expand_vars => 1);
1440 $ssh->set_var(ID => 42);
1441 $ssh->system("ls >/tmp/ls.out-%HOST%-%ID%");
1442 will redirect the output of the "ls" command to
1444 "/tmp/ls.out-server.foo.com-42" on the remote host.
1445 Tunnels
1447 Besides running commands on the remote host, Net::OpenSSH also allows
1448 one to tunnel TCP connections to remote machines reachable from the SSH
1449 server.
1450 That feature is made available through the "tunnel" option of the
1452 "open_ex" method, and also through wrapper methods "open_tunnel" and
1453 "capture_tunnel" and most others where it makes sense.
1454 Example:
1456 $ssh->system({tunnel => 1,
1458 stdin_data => "GET / HTTP/1.0\r\n\r\n",
1459 stdout_file => "/tmp/$server.res"},
1460 $server, 80)
1461 or die "unable to retrieve page: " . $ssh->error;
1462 or capturing the output of several requests in parallel:
1464 my @pids;
1466 for (@servers) {
1467 my $pid = $ssh->spawn({tunnel => 1,
1468 stdin_file => "/tmp/request.req",
1469 stdout_file => "/tmp/$_.res"},
1470 $_, 80);
1471 if ($pid) {
1472 push @pids, $pid;
1473 }
1474 else {
1475 warn "unable to spawn tunnel process to $_: " . $ssh->error;
1476 }
1477 }
1478 waitpid ($_, 0) for (@pids);
1479 Under the hood, in order to create a tunnel, a new "ssh" process is
1481 spawned with the option "-W${address}:${port}" (available from OpenSSH
1482 5.4 and upwards) making it redirect its stdio streams to the remote
1483 given address. Unlike when "ssh" "-L" options is used to create
1484 tunnels, no TCP port is opened on the local machine at any time so this
1485 is a perfectly secure operation.
1486 The PID of the new process is returned by the named methods. It must be
1488 reaped once the pipe or socket handlers for the local side of the
1489 tunnel have been closed.
1490 OpenSSH 5.4 or later is required for the tunnels functionality to work.
1492 Also, note that tunnel forwarding may be administratively forbidden at
1493 the server side (see sshd(8) and sshd_config(5) or the documentation
1494 provided by your SSH server vendor).
1495 Tunnels targeting UNIX sockets
1497 When connecting to hosts running a recent version of OpenSSH sshd, it
1499 is also possible to open connections targeting Unix sockets.
1500 For instance:
1502 my $response = $ssh->capture({tunnel => 1, stdin_data => $request },
1504 "/tmp/socket-foo");
1505 Currently, this feature requires a patched OpenSSH ssh client. The
1507 patch is available as
1508 "patches/openssh-fwd-stdio-to-streamlocal-1.patch".
1509 Port forwarding
1511 Net::OpenSSH does not offer direct support for handling port
1513 forwardings between server and client. But that can be done easily
1514 anyway passing custom SSH options to its methods.
1515 For instance, tunnel creation options can be passed to the constructor:
1517 my $ssh = Net::OpenSSH->new(...
1519 master_opts => -Llocalhost:1234:localhost:3306');
1520 The port forwardings can also be changed for a running SSH connection
1522 using a Control command:
1523 # setting up a tunnel:
1525 $ssh->system({ssh_opts => ['-O','forward',
1526 '-L127.0.0.1:12345:127.0.0.1:3306']});
1527 # canceling it:
1529 $ssh->system({ssh_opts => ['-O', 'cancel',
1530 '-L127.0.0.1:12345:127.0.0.1:3306']});
1531 Data encoding
1533 Net::OpenSSH has some support for transparently converting the data
1534 send or received from the remote server to Perl internal unicode
1535 representation.
1536 The methods supporting that feature are those that move data from/to
1538 Perl data structures (e.g. "capture", "capture2", "capture_tunnel" and
1539 methods supporting the "stdin_data" option). Data accessed through
1540 pipes, sockets or redirections is not affected by the encoding options.
1541 It is also possible to set the encoding of the command and arguments
1543 passed to the remote server on the command line.
1544 By default, if no encoding option is given on the constructor or on the
1546 method calls, Net::OpenSSH will not perform any encoding
1547 transformation, effectively processing the data as "latin1".
1548 When data can not be converted between the Perl internal representation
1550 and the selected encoding inside some Net::OpenSSH method, it will fail
1551 with an "OSSH_ENCODING_ERROR" error.
1552 The supported encoding options are as follows:
1554 stream_encoding => $encoding
1556 sets the encoding of the data send and received on capture methods.
1557 argument_encoding => $encoding
1559 sets the encoding of the command line arguments
1560 encoding => $encoding
1562 sets both "argument_encoding" and "stream_encoding".
1563 The constructor also accepts "default_encoding",
1565 "default_stream_encoding" and "default_argument_encoding" that set the
1566 defaults.
1567 Diverting "new"
1569 When a code ref is installed at $Net::OpenSSH::FACTORY, calls to new
1570 will be diverted through it.
1571 That feature can be used to transparently implement connection caching,
1573 for instance:
1574 my $old_factory = $Net::OpenSSH::FACTORY;
1576 my %cache;
1577 sub factory {
1579 my ($class, %opts) = @_;
1580 my $signature = join("\0", $class, map { $_ => $opts{$_} }, sort keys %opts);
1581 my $old = $cache{signature};
1582 return $old if ($old and $old->error != OSSH_MASTER_FAILED);
1583 local $Net::OpenSSH::FACTORY = $old_factory;
1584 $cache{$signature} = $class->new(%opts);
1585 }
1586 $Net::OpenSSH::FACTORY = \&factory;
1588 ... and I am sure it can be abused in several other ways!
1590
1592 Expect
1593 Sometimes you would like to use Expect to control some program running
1594 in the remote host. You can do it as follows:
1595 my ($pty, $pid) = $ssh->open2pty(@cmd)
1597 or die "unable to run remote command @cmd";
1598 my $expect = Expect->init($pty);
1599 Then, you will be able to use the new Expect object in $expect as
1601 usual.
1602 Net::Telnet
1604 This example is adapted from Net::Telnet documentation:
1605 my ($pty, $pid) = $ssh->open2pty({stderr_to_stdout => 1})
1607 or die "unable to start remote shell: " . $ssh->error;
1608 my $telnet = Net::Telnet->new(-fhopen => $pty,
1609 -prompt => '/.*\$ $/',
1610 -telnetmode => 0,
1611 -cmd_remove_mode => 1,
1612 -output_record_separator => "\r");
1613 $telnet->waitfor(-match => $telnet->prompt,
1615 -errmode => "return")
1616 or die "login failed: " . $telnet->lastline;
1617 my @lines = $telnet->cmd("who");
1619 ...
1621 $telnet->close;
1623 waitpid($pid, 0);
1624 mod_perl and mod_perl2
1626 mod_perl and mod_perl2 tie STDIN and STDOUT to objects that are not
1627 backed up by real file descriptors at the operating system level.
1628 Net::OpenSSH will fail if any of these handles is used explicitly or
1629 implicitly when calling some remote command.
1630 The work-around is to redirect them to "/dev/null" or to some file:
1632 open my $def_in, '<', '/dev/null' or die "unable to open /dev/null";
1634 my $ssh = Net::OpenSSH->new($host,
1635 default_stdin_fh => $def_in);
1636 my $out = $ssh->capture($cmd1);
1638 $ssh->system({stdout_discard => 1}, $cmd2);
1639 $ssh->system({stdout_to_file => '/tmp/output'}, $cmd3);
1640 Also, note that from a security stand point, running "ssh" from inside
1642 the web server process is not a great idea. An attacker exploiting some
1643 Apache bug would be able to access the SSH keys and passwords and gain
1644 unlimited access to the remote systems.
1645 If you can, use a queue (as TheSchwartz) or any other mechanism to
1647 execute the ssh commands from another process running under a different
1648 user account.
1649 At a minimum, ensure that "~www-data/.ssh" (or similar) is not
1651 accessible through the web server!
1652 Net::SFTP::Foreign
1654 See method "sftp".
1655 Net::SSH::Any
1657 See method "any".
1658 Object::Remote
1660 See method "object_remote".
1661 AnyEvent (and similar frameworks)
1663 Net::OpenSSH provides all the functionality required to be integrated
1664 inside event oriented programming framework such as AnyEvent or
1665 IO::Async in the following way:
1666 1. Create a disconnected Net::OpenSSH object:
1668 my $ssh = Net::OpenSSH->new($host, async => 1, ...);
1669 2. Let the object connect to the remote host:
1671 Use a timer to call the "wait_for_master" method in async mode
1672 repeatedly until it returns a true value indicating success.
1673 Also, the object error state needs to be checked after every call
1675 in order to detect failed connections. For instance:
1676 my $ssh = Net::OpenSSH->new(..., async => 1);
1678 my $w;
1679 $w = AE::timer 0.1, 0.1, sub {
1680 if ($ssh->wait_for_master(1)) {
1681 # the connection has been established!
1682 # remote commands can be run now
1683 undef $w;
1684 on_ssh_success(...);
1685 }
1686 elsif ($ssh->error) {
1687 # connection can not be established
1688 undef $w;
1689 on_ssh_failure(...);
1690 }
1691 }
1692 3. Use the event framework to launch the remote processes:
1694 Call Net::OpenSSH "make_remote_command" to construct commands which
1695 can be run using the framework regular facilities for launching
1696 external commands.
1697 Error checking should also be performed at this point because the
1699 SSH connection could be broken.
1700 For instance:
1702 if (defined(my $cmd = $ssh->make_remote_command(echo => 'hello!')) {
1704 AnyEvent::Util::run_cmd($cmd, %run_cmd_opts);
1705 }
1706 else {
1707 # something went wrong!
1708 }
1709 Alternatively, any of the "open*" methods provided by Net::OpenSSH
1711 could also be used to launch remote commands.
1712 4. When finished, disconnect asynchronously
1714 After initiating an asynchronous disconnect with disconnect(1),
1715 repeatedly call "wait_for_master" until you get a defined but false
1716 value:
1717 $ssh->disconnect(1);
1719 my $w; $w = AE::timer 0.1, 0.1, sub {
1721 my $res = $ssh->wait_for_master(1);
1722 if (defined $res && !$res) {
1724 undef $w;
1725 undef $ssh;
1726 }
1727 };
1728 Be careful not to let the $ssh object go out of scope until the
1730 disconnection has finished, otherwise its destructor will wait and
1731 block your program until the disconnection has completed.
1732 Other modules
1734 CPAN contains several modules that rely on SSH to perform their duties
1735 as for example IPC::PerlSSH or GRID::Machine.
1736 Often, it is possible to instruct them to go through a Net::OpenSSH
1738 multiplexed connection employing some available constructor option. For
1739 instance:
1740 use Net::OpenSSH;
1742 use IPC::PerlIPC;
1743 my $ssh = Net::OpenSSH->new(...);
1744 $ssh->error and die "unable to connect to remote host: " . $ssh->error;
1745 my @cmd = $ssh->make_remote_command('/usr/bin/perl');
1746 my $ipc = IPC::PerlSSH->new(Command => \@cmd);
1747 my @r = $ipc->eval('...');
1748 or...
1750 use GRID::Machine;
1752 ...
1753 my @cmd = $ssh->make_remote_command('/usr/bin/perl');
1754 my $grid = GRID::Machine->new(command => \@cmd);
1755 my $r = $grid->eval('print "hello world!\n"');
1756 In other cases, some kind of plugin mechanism is provided by the 3rd
1758 party modules to allow for different transports. The method "open2" may
1759 be used to create a pair of pipes for transport in these cases.
1760
1762 Usually, Net::OpenSSH works out of the box, but when it fails, some
1763 users have a hard time finding the cause of the problem. This mini
1764 troubleshooting guide should help you to find and solve it.
1765 1 - check the error message
1767 Add in your script, after the Net::OpenSSH constructor call, an
1768 error check:
1769 $ssh = Net::OpenSSH->new(...);
1771 $ssh->error and die "SSH connection failed: " . $ssh->error;
1772 The error message will tell what has gone wrong.
1774 2 - Check the connection parameters
1776 Believe it or not, passing bad parameters to Net::OpenSSH turns to
1777 be one of the top causes of failures so check that you are using
1778 the right parameters.
1779 Specifically, if you are obtaining them from the outside, ensure
1781 that they don't have extra spaces or new lines attached (do you
1782 need to "chomp"?).
1783 Passwords and URIs may contain "$" or "@" characters. If you have
1785 then hardcoded in your script, check that those are quoted properly
1786 (and BTW, use "strict").
1787 3 - OpenSSH version
1789 Ensure that you have a version of "ssh" recent enough:
1790 $ ssh -V
1792 OpenSSH_5.1p1 Debian-5, OpenSSL 0.9.8g 19 Oct 2007
1793 OpenSSH version 4.1 was the first to support the multiplexing
1795 feature and is the minimal required by the module to work. I advise
1796 you to use the latest OpenSSH (currently 7.5).
1797 The "ssh_cmd" constructor option lets you select the "ssh" binary
1799 to use. For instance:
1800 $ssh = Net::OpenSSH->new($host,
1802 ssh_cmd => "/opt/OpenSSH/5.8/bin/ssh")
1803 Some hardware vendors (e.g. Sun, err... Oracle) include custom
1805 versions of OpenSSH bundled with the operating system. In
1806 principle, Net::OpenSSH should work with these SSH clients as long
1807 as they are derived from some version of OpenSSH recent enough.
1808 Anyway, my advise is to use the real OpenSSH software if you can!
1809 4 - run ssh from the command line
1811 Check you can connect to the remote host using the same parameters
1812 you are passing to Net::OpenSSH. In particular, ensure that you are
1813 running "ssh" as the same local user.
1814 If you are running your script from a web server, the user would
1816 probably be "www", "apache" or something alike.
1817 Common problems are:
1819 • Remote host public key not present in known_hosts file.
1821 The SSH protocol uses public keys to identify the remote hosts
1823 so that they can not be supplanted by some malicious third
1824 parties.
1825 For OpenSSH, usually the server public key is stored in
1827 "/etc/ssh/ssh_host_dsa_key.pub" or in
1828 "/etc/ssh/ssh_host_rsa_key.pub" and that key should be copied
1829 into the "~/.ssh/known_hosts" file in the local machine (other
1830 SSH implementations may use other file locations).
1831 Maintaining the server keys when several hosts and clients are
1833 involved may be somewhat inconvenient, so most SSH clients, by
1834 default, when a new connection is established to a host whose
1835 key is not in the "known_hosts" file, show the key and ask the
1836 user if he wants the key copied there.
1837 • Wrong remote host public key in known_hosts file.
1839 This is another common problem that happens when some server is
1841 replaced or reinstalled from scratch and its public key changes
1842 becoming different to that installed on the "known_hosts" file.
1843 The easiest way to solve that problem is to remove the old key
1845 from the "known_hosts" file by hand using any editor and then
1846 to connect to the server replying "yes" when asked to save the
1847 new key.
1848 • Wrong permissions for the "~/.ssh" directory or its contents.
1850 OpenSSH client performs several checks on the access
1852 permissions of the "~/.ssh" directory and its contents and
1853 refuses to use them when misconfigured. See the FILES section
1854 from the ssh(1) man page.
1855 • Incorrect settings for password or public key authentication.
1857 Check that you are using the right password or that the user
1859 public key is correctly installed on the server.
1860 5 - security checks on the multiplexing socket
1862 Net::OpenSSH performs some security checks on the directory where
1863 the multiplexing socket is going to be placed to ensure that it can
1864 not be accessed by other users.
1865 The default location for the multiplexing socket is under
1867 "~/.libnet-openssh-perl". It can be changed using the "ctl_dir" and
1868 "ctl_path" constructor arguments.
1869 The requirements for that directory and all its parents are:
1871 • They have to be owned by the user executing the script or by
1873 root
1874 • Their permission masks must be 0755 or more restrictive, so
1876 nobody else has permissions to perform write operations on
1877 them.
1878 The constructor option "strict_mode" disables these security
1880 checks, but you should not use it unless you understand its
1881 implications.
1882 6 - file system must support sockets
1884 Some file systems (as for instance FAT or AFS) do not support
1885 placing sockets inside them.
1886 Ensure that the "ctl_dir" path does not lay into one of those file
1888 systems.
1889
1891 Debugging of Net::OpenSSH internals is controlled through the variable
1892 $Net::OpenSSH::debug. Every bit of this variable activates debugging of
1893 some subsystem as follows:
1894 bit 1 - errors
1896 Dumps changes on the internal object attribute where errors are
1897 stored.
1898 bit 2 - ctl_path
1900 Dumps information about ctl_path calculation and the tests
1901 performed on that directory in order to decide if it is secure to
1902 place the multiplexing socket inside.
1903 bit 4 - connecting
1905 Dumps information about the establishment of new master
1906 connections.
1907 bit 8 - commands and arguments
1909 Dumps the command and arguments for every system/exec call.
1910 bit 16 - command execution
1912 Dumps information about the progress of command execution.
1913 bit 32 - destruction
1915 Dumps information about the destruction of Net::OpenSSH objects and
1916 the termination of the SSH master processes.
1917 bit 64 - IO loop
1919 Dumps information about the progress of the IO loop on capture
1920 operations.
1921 bit 128 - IO hexdumps
1923 Generates hexdumps of the information that travels through the SSH
1924 streams inside capture operations.
1925 bit 512 - OS tracing of the master process
1927 Use the module Net::OpenSSH::OSTracer to trace the SSH master
1928 process at the OS level.
1929 For instance, in order to activate all the debugging flags, you can
1931 use:
1932 $Net::OpenSSH::debug = ~0;
1934 Note that the meaning of the flags and the information generated is
1936 only intended for debugging of the module and may change without notice
1937 between releases.
1938 If you are using password authentication, enabling debugging for
1940 IO::Tty may also show interesting information:
1941 $IO::Tty::DEBUG = 1;
1943 Finally, by default debugging output is sent to "STDERR". You can
1945 override it pointing $Net::OpenSSH::debug_fh to a different file
1946 handle. For instance:
1947 BEGIN {
1949 open my $out, '>', '/tmp/debug.txt' or warn $!;
1950 $Net::OpenSSH::debug_fh = $out;
1951 $Net::OpenSSH::debug = -1;
1952 }
1953
1955 Q: Is this module secure?
1956 A: Well, it tries to be!
1958 From a security standpoint the aim of this module is to be as secure as
1960 OpenSSH, your operating system, your shell and in general your
1961 environment allow it to be.
1962 It does not take any shortcut just to make your life easier if that
1964 means lowering the security level (for instance, disabling
1965 "StrictHostKeyChecking" by default).
1966 In code supporting features that are not just proxied to OpenSSH, the
1968 module tries to keep the same standards of security as OpenSSH (for
1969 instance, checking directory and file permissions when placing the
1970 multiplexing socket).
1971 On the other hand, and keeping with OpenSSH philosophy, the module lets
1973 you disable most (all?) of those security measures. But just because it
1974 lets you do it it doesn't mean it is a good idea to do so!!!
1975 If you are a novice programmer or SSH user, and googling you have just
1977 found some flag that you don't understand but that seems to magically
1978 solve your connection problems... well, believe me, it is probably a
1979 bad idea to use it. Ask somebody how really knows first!
1980 Just to make thinks clear, if your code contains any of the keywords
1982 from the (non-exclusive) list below and you don't know why, you are
1983 probably wrecking the security of the SSH protocol:
1984 strict_mode
1986 StrictHostKeyChecking
1987 UserKnownHostsFile
1988 Other considerations related to security you may like to know are as
1990 follows:
1991 Taint mode
1993 The module supports working in taint mode.
1994 If you are in an exposed environment, you should probably enable it
1996 for your script in order to catch any unchecked command for being
1997 executed in the remote side.
1998 Web environments
2000 It is a bad idea to establish SSH connections from your webserver
2001 because if it becomes compromised in any way, the attacker would be
2002 able to use the credentials from your script to connect to the
2003 remote host and do anything he wishes there.
2004 Command quoting
2006 The module can quote commands and arguments for you in a flexible
2007 and powerful way.
2008 This is a feature you should use as it reduces the possibility of
2010 some attacker being able to inject and run arbitrary commands on
2011 the remote machine (and even for scripts that are not exposed it is
2012 always advisable to enable argument quoting).
2013 Having said that, take into consideration that argument-quoting is
2015 just a hack to emulate the invoke-without-a-shell feature of Perl
2016 builtins such as "system" and alike. There may be bugs(*) on the
2017 quoting code, your particular shell may have different quoting
2018 rules with unhandled corner cases or whatever. If your script is
2019 exposed to the outside, you should check your inputs and restrict
2020 what you accept as valid.
2021 [* even if this is one of the parts of the module more intensively
2023 tested!]
2024 Shellshock
2026 (see Shellshock
2027 <http://en.wikipedia.org/wiki/Shellshock_%28software_bug%29>)
2028 When executing local commands, the module always avoids calling the
2030 shell so in this way it is not affected by Shellshock.
2031 Unfortunately, some commands ("scp", "rsync" and "ssh" when the
2033 "ProxyCommand" option is used) invoke other commands under the hood
2034 using the user shell. That opens the door to local Shellshock
2035 exploitation.
2036 On the remote side invocation of the shell is unavoidable due to
2038 the protocol design.
2039 By default, SSH does not forward environment variables but some
2041 Linux distributions explicitly change the default OpenSSH
2042 configuration to enable forwarding and acceptance of some specific
2043 ones (for instance "LANG" and "LC_*" on Debian and derivatives,
2044 Fedora does alike) and this also opens the door to Shellshock
2045 exploitation.
2046 Note that the shell used to invoke commands is not "/bin/sh" but
2048 the user shell as configured in "/etc/passwd", PAM or whatever
2049 authentication subsystem is used by the local or remote operating
2050 system. Debian users, don't think you are not affected because your
2051 "/bin/sh" points to "dash"!
2052
2054 Frequent questions about the module:
2055 Connecting to switches, routers, etc.
2057 Q: I can not get the method "system", "capture", etc., to work when
2058 connecting to some router, switch, etc. What I am doing wrong?
2059 A: Roughly, the SSH protocol allows for two modes of operation:
2061 command mode and interactive mode.
2062 Command mode is designed to run single commands on the remote host.
2064 It opens a SSH channel between both hosts, asks the remote computer
2065 to run some given command and when it finishes, the channel is
2066 closed. It is what you get, for instance, when you run something
2067 as...
2068 $ ssh my.unix.box cat foo.txt
2070 ... and it is also the way Net::OpenSSH runs commands on the remote
2072 host.
2073 Interactive mode launches a shell on the remote hosts with its
2075 stdio streams redirected to the local ones so that the user can
2076 transparently interact with it.
2077 Some devices (as probably the one you are using) do not run an
2079 standard, general purpose shell (e.g. "bash", "csh" or "ksh") but
2080 some custom program specially targeted and limited to the task of
2081 configuring the device.
2082 Usually, the SSH server running on these devices does not support
2084 command mode. It unconditionally attaches the restricted shell to
2085 any incoming SSH connection and waits for the user to enter
2086 commands through the redirected stdin stream.
2087 The only way to work-around this limitation is to make your script
2089 talk to the restricted shell (1-open a new SSH session, 2-wait for
2090 the shell prompt, 3-send a command, 4-read the output until you get
2091 to the shell prompt again, repeat from 3). The best tool for this
2092 task is probably Expect, used alone or combined with Net::OpenSSH
2093 (see "Expect").
2094 There are some devices that support command mode but that only
2096 accept one command per connection. In that cases, using Expect is
2097 also probably the best option.
2098 Nowadays, there is a new player, Net::CLI::Interact that may be
2100 more suitable than Expect, and Net::Appliance::Session for working
2101 specifically with network devices.
2102 Connection fails
2104 Q: I am unable to make the module connect to the remote host...
2105 A: Have you read the troubleshooting section? (see
2107 "TROUBLESHOOTING").
2108 Disable StrictHostKeyChecking
2110 Q: Why is "ssh" not run with "StrictHostKeyChecking=no"?
2111 A: Using "StrictHostKeyChecking=no" relaxes the default security
2113 level of SSH and it will be relatively easy to end with a
2114 misconfigured SSH (for instance, when "known_hosts" is unwritable)
2115 that could be forged to connect to a bad host in order to perform
2116 man-in-the-middle attacks, etc.
2117 I advice you to do not use that option unless you fully understand
2119 its implications from a security point of view.
2120 If you want to use it anyway, past it to the constructor:
2122 $ssh = Net::OpenSSH->new($host,
2124 master_opts => [-o => "StrictHostKeyChecking=no"],
2125 ...);
2126 child process STDIN/STDOUT/STDERR is not a real system file handle
2128 Q: Calls to "system", "capture", etc. fail with the previous error,
2129 what's happening?
2130 A: The reported stdio stream is closed or is not attached to a real
2132 file handle (e.g. it is a tied handle). Redirect it to "/dev/null"
2133 or to a real file:
2134 my $out = $ssh->capture({stdin_discard => 1, stderr_to_stdout => 1},
2136 $cmd);
2137 See also the mod_perl entry above.
2139 Solaris (and AIX and probably others)
2141 Q: I was trying Net::OpenSSH on Solaris and seem to be running into
2142 an issue...
2143 A: The SSH client bundled with Solaris is an early fork of OpenSSH
2145 that does not provide the multiplexing functionality required by
2146 Net::OpenSSH. You will have to install the OpenSSH client.
2147 Precompiled packages are available from Sun Freeware
2149 (<http://www.sunfreeware.com>). There, select your OS version an
2150 CPU architecture, download the OpenSSH package and its dependencies
2151 and install them. Note that you do not need to configure Solaris to
2152 use the OpenSSH server "sshd".
2153 Ensure that OpenSSH client is in your path before the system "ssh"
2155 or alternatively, you can hardcode the full path into your scripts
2156 as follows:
2157 $ssh = Net::OpenSSH->new($host,
2159 ssh_cmd => '/usr/local/bin/ssh');
2160 AIX and probably some other unixen, also bundle SSH clients lacking
2162 the multiplexing functionality and require installation of the real
2163 OpenSSH.
2164 Can not change working directory
2166 Q: I want to run some command inside a given remote directory but I
2167 am unable to change the working directory. For instance:
2168 $ssh->system('cd /home/foo/bin');
2170 $ssh->systen('ls');
2171 does not list the contents of "/home/foo/bin".
2173 What am I doing wrong?
2175 A: Net::OpenSSH (and, for that matter, all the SSH modules
2177 available from CPAN but Net::SSH::Expect) run every command in a
2178 new session so most shell builtins that are run for its side
2179 effects become useless (e.g. "cd", "export", "ulimit", "umask",
2180 etc., usually, you can list them running "help" from the shell).
2181 A work around is to combine several commands in one, for instance:
2183 $ssh->system('cd /home/foo/bin && ls');
2185 Note the use of the shell "&&" operator instead of ";" in order to
2187 abort the command as soon as any of the subcommands fail.
2188 Also, several commands can be combined into one while still using
2190 the multi-argument quoting feature as follows:
2191 $ssh->system(@cmd1, \\'&&', @cmd2, \\'&&', @cmd3, ...);
2193 Running detached remote processes
2195 Q: I need to be able to ssh into several machines from my script,
2196 launch a process to run in the background there, and then return
2197 immediately while the remote programs keep running...
2198 A: If the remote systems run some Unix/Linux variant, the right
2200 approach is to use nohup(1) that will disconnect the remote process
2201 from the stdio streams and to ask the shell to run the command on
2202 the background. For instance:
2203 $ssh->system("nohup $long_running_command &");
2205 Also, it may be possible to demonize the remote program. If it is
2207 written in Perl you can use App::Daemon for that (actually, there
2208 are several CPAN modules that provided that kind of functionality).
2209 In any case, note that you should not use "spawn" for that.
2211 MaxSessions server limit reached
2213 Q: I created an $ssh object and then fork a lot children processes
2214 which use this object. When the children number is bigger than
2215 "MaxSessions" as defined in sshd configuration (defaults to 10),
2216 trying to fork new remote commands will prompt the user for the
2217 password.
2218 A: When the slave SSH client gets a response from the remote
2220 servers saying that the maximum number of sessions for the current
2221 connection has been reached, it fall backs to open a new direct
2222 connection without going through the multiplexing socket.
2223 To stop that for happening, the following hack can be used:
2225 $ssh = Net::OpenSSH->new(host,
2227 default_ssh_opts => ['-oConnectionAttempts=0'],
2228 ...);
2229 Running remote commands with sudo
2231 Q: How can I run remote commands using "sudo" to become root first?
2232 A: The simplest way is to tell "sudo" to read the password from
2234 stdin with the "-S" flag and to do not use cached credentials with
2235 the "-k" flag. You may also like to use the "-p" flag to tell
2236 "sudo" to print an empty prompt. For instance:
2237 my @out = $ssh->capture({ stdin_data => "$sudo_passwd\n" },
2239 'sudo', '-Sk',
2240 '-p', '',
2241 '--',
2242 @cmd);
2243 If the version of sudo installed on the remote host does not
2245 support the "-S" flag (it tells sudo to read the password from its
2246 STDIN stream), you can do it as follows:
2247 my @out = $ssh->capture({ tty => 1,
2249 stdin_data => "$sudo_passwd\n" },
2250 'sudo', '-k',
2251 '-p', '',
2252 '--',
2253 @cmd);
2254 This may generate an spurious and harmless warning from the SSH
2256 master connection (because we are requesting allocation of a tty on
2257 the remote side and locally we are attaching it to a regular pair
2258 of pipes).
2259 If for whatever reason the methods described above fail, you can
2261 always revert to using Expect to talk to the remote "sudo". See the
2262 "examples/expect.pl" script from this module distribution.
2263
2265 OpenSSH client documentation ssh(1), ssh_config(5), the project web
2266 <http://www.openssh.org> and its FAQ
2267 <http://www.openbsd.org/openssh/faq.html>. scp(1) and rsync(1). The
2268 OpenSSH Wikibook <http://en.wikibooks.org/wiki/OpenSSH>.
2269 Net::OpenSSH::Gateway for detailed instruction about how to get this
2271 module to connect to hosts through proxies and other SSH gateway
2272 servers.
2273 Core perl documentation perlipc, "open" in perlfunc, "waitpid" in
2275 perlfunc.
2276 IO::Pty to known how to use the pseudo tty objects returned by several
2278 methods on this package.
2279 Net::SFTP::Foreign provides a compatible SFTP implementation.
2281 Expect can be used to interact with commands run through this module on
2283 the remote machine (see also the "expect.pl" and <autosudo.pl> scripts
2284 in the examples directory).
2285 SSH::OpenSSH::Parallel is an advanced scheduler that allows one to run
2287 commands in remote hosts in parallel. It is obviously based on
2288 Net::OpenSSH.
2289 SSH::Batch allows one to run remote commands in parallel in a cluster.
2291 It is build on top on "Net::OpenSSH" also.
2292 Other Perl SSH clients: Net::SSH::Perl, Net::SSH2, Net::SSH,
2294 Net::SSH::Expect, Net::SCP, Net::SSH::Mechanize.
2295 Net::OpenSSH::Compat is a package offering a set of compatibility
2297 layers for other SSH modules on top of Net::OpenSSH.
2298 IPC::PerlSSH, GRID::Machine allow execution of Perl code in remote
2300 machines through SSH.
2301 SSH::RPC implements an RPC mechanism on top of SSH using Net::OpenSSH
2303 to handle the connections.
2304 Net::CLI::Interact allows one to interact with remote shells and other
2306 services. It is specially suited for interaction with network
2307 equipment. The phrasebook approach it uses is very clever. You may also
2308 like to check the other modules <https://metacpan.org/author/OLIVER>
2309 from its author, Oliver Gorwits.
2310
2312 Experimental features
2313 Support for the "restart" feature is experimental.
2314 Object::Remote integration is highly experimental.
2316 Support for tunnels targeting Unix sockets is highly experimental.
2318 Support for the "setpgrp" feature is highly experimental.
2320 Support for the gateway feature is highly experimental and mostly
2322 stalled.
2323 Support for taint mode is experimental.
2325 Known issues
2327 Net::OpenSSH does not work on Windows. OpenSSH multiplexing feature
2328 requires passing file handles through sockets, something that is not
2329 supported by any version of Windows.
2330 It does not work on VMS either... well, probably, it does not work on
2332 anything not resembling a modern Linux/Unix OS.
2333 Old versions of OpenSSH "ssh" may leave stdio streams in non-blocking
2335 mode. That can result on failures when writing to "STDOUT" or "STDERR"
2336 after using the module. In order to work-around this issue, Perl
2337 "fcntl" in perlfunc can be used to unset the non-blocking flag:
2338 use Fcntl qw(F_GETFL F_SETFL O_NONBLOCK);
2340 my $flags = fcntl(STDOUT, F_GETFL, 0);
2341 fcntl(STDOUT, F_SETFL, $flags & ~O_NONBLOCK);
2342 Reporting bugs and asking for help
2344 To report bugs send an email to the address that appear below or use
2345 the CPAN bug tracking system at <http://rt.cpan.org>.
2346 Post questions related to how to use the module in PerlMonks
2348 <http://perlmonks.org/>, you will probably get faster responses than if
2349 you address me directly and I visit PerlMonks quite often, so I will
2350 see your question anyway.
2351 Commercial support
2353 Commercial support, professional services and custom software
2354 development around this module are available through my current
2355 company. Drop me an email with a rough description of your requirements
2356 and we will get back to you ASAP.
2357 My wishlist
2359 If you like this module and you are feeling generous, take a look at my
2360 Amazon Wish List: <http://amzn.com/w/1WU1P6IR5QZ42>.
2361 Also consider contributing to the OpenSSH project this module builds
2363 upon: <http://www.openssh.org/donations.html>.
2364
2366 - Tests for "scp_*", "rsync_*" and "sftp" methods
2367 - Make "pipe_in" and "pipe_out" methods "open_ex" based
2369 - "auto_discard_streams" feature for mod_perl2 and similar environments
2371 - Refactor open_ex support for multiple commands, maybe just keeping
2373 tunnel, ssh and raw
2374 Send your feature requests, ideas or any feedback, please!
2376
2378 The source code of this module is hosted at GitHub:
2379 <http://github.com/salva/p5-Net-OpenSSH>.
2380 Code contributions to the module are welcome but you should obey the
2382 following rules:
2383 Only Perl 5.8.4 required
2385 Yes, that's pretty old, but Net::OpenSSH is intended to be also
2386 used by system administrators that sometimes have to struggle with
2387 old systems. The reason to pick 5.8.4 is that it has been the
2388 default perl on Solaris for a long time.
2389 Avoid the "All the world's a Linux PC" syndrome
2391 The module should work on any (barely) sane Unix or Linux operating
2392 system. Specially, it should not be assumed that the over-featured
2393 GNU utilities and toolchain are available.
2394 Dependencies are optional
2396 In order to make the module very easy to install, no mandatory
2397 dependencies on other CPAN modules are allowed.
2398 Optional modules, that are loaded only on demand, are acceptable
2400 when they are used for adding new functionality (as it is done, for
2401 instance, with IO::Pty).
2402 Glue code for integration with 3rd party modules is also allowed
2404 (as it is done with Expect).
2405 Usage of language extension modules and alike is not acceptable.
2407 Tests should be lax
2409 We don't want false negatives when testing. In case of doubt tests
2410 should succeed.
2411 Also, in case of tests invoking some external program, it should be
2413 checked that the external program is available and that it works as
2414 expected or otherwise skip those tests.
2415 Backward compatibility
2417 Nowadays Net::OpenSSH is quite stable and there are lots of scripts
2418 out there using it that we don't want to break, so, keeping the API
2419 backward compatible is a top priority.
2420 Probably only security issues could now justify a backward
2422 incompatible change.
2423 Follow my coding style
2425 Look at the rest of the code.
2426 I let Emacs do the formatting for me using cperl-mode PerlStyle.
2428 Talk to me
2430 Before making a large change or implementing a new feature get in
2431 touch with me.
2432 I may have my own ideas about how things should be done. It is
2434 better if you know them before hand, otherwise, you risk getting
2435 your patch rejected.
2436 Well, actually you should know that I am quite good at rejecting
2438 patches but it is not my fault!
2439 Most of the patches I get are broken in some way: they don't follow the
2441 main module principles, sometimes the author didn't get the full
2442 picture and solved the issue in a short-sighted way, etc.
2443 In any case, you should not be discouraged to contribute. Even if your
2445 patch is not applied directly, seeing how it solves your requirements
2446 or, in the case of bugs, the underlying problem analysis may be very
2447 useful and help me to do it... my way.
2448 I always welcome documentation corrections and improvements.
2450
2452 Copyright (C) 2008-2022 by Salvador Fandiño (sfandino@yahoo.com)
2453 This library is free software; you can redistribute it and/or modify it
2455 under the same terms as Perl itself, either Perl version 5.10.0 or, at
2456 your option, any later version of Perl 5 you may have available.
2457perl v5.36.0 2023-01-20 Net::OpenSSH(3)