1Net::SSH::Expect(3) User Contributed Perl Documentation Net::SSH::Expect(3)
2
6 Net::SSH::Expect - SSH wrapper to execute remote commands
7
9 use Net::SSH::Expect;
10 #
12 # You can do SSH authentication with user-password or without it.
13 #
14 # Making an ssh connection with user-password authentication
16 # 1) construct the object
17 my $ssh = Net::SSH::Expect->new (
18 host => "myserver.com",
19 password=> 'pass87word',
20 user => 'bnegrao',
21 raw_pty => 1
22 );
23 # 2) logon to the SSH server using those credentials.
25 # test the login output to make sure we had success
26 my $login_output = $ssh->login();
27 if ($login_output !~ /Welcome/) {
28 die "Login has failed. Login output was $login_output";
29 }
30 # - now you know you're logged in - #
32 # Starting ssh without password
34 # 1) run the constructor
35 my $ssh = Net::SSH::Expect->new (
36 host => "myserver.com",
37 user => 'bnegrao',
38 raw_pty => 1
39 );
40 # 2) now start the ssh process
41 $ssh->run_ssh() or die "SSH process couldn't start: $!";
42 # 3) you should be logged on now. Test if you received the remote prompt:
44 ($ssh->read_all(2) =~ />\s*\z/) or die "where's the remote prompt?"
45 # - now you know you're logged in - #
47 # disable terminal translations and echo on the SSH server
49 # executing on the server the stty command:
50 $ssh->exec("stty raw -echo");
51 # runs arbitrary commands and print their outputs
53 # (including the remote prompt comming at the end)
54 my $ls = $ssh->exec("ls -l /");
55 print($ls);
56 my $who = $ssh->exec("who");
58 print ($who);
59 # When running a command that causes a huge output,
61 # lets get the output line by line:
62 $ssh->send("find /"); # using send() instead of exec()
63 my $line;
64 # returns the next line, removing it from the input stream:
65 while ( defined ($line = $ssh->read_line()) ) {
66 print $line . "\n";
67 }
68 # take a look in what is immediately available on the input stream
70 print $ssh->peek(0); # you'll probably see the remote prompt
71 # the last read_line() on the previous loop will not include the
73 # remote prompt that appears at the end of the output, because the prompt
74 # doesn't end with a '\n' character. So let's remove the remainder
75 # prompt from the input stream:
76 $ssh->eat($ssh->peek(0)); # removes whatever is on the input stream now
77 # We can also iterate over the output in chunks,
79 # printing everything that's available at each 1 second:
80 $ssh->send ("find /home");
81 my $chunk;
82 while ($chunk = $ssh->peek(1)) { # grabs chunks of output each 1 second
83 print $ssh->eat($chunk);
84 }
85 # Now let's run an interactive command, like passwd.
87 # This is done combining send() and waitfor() methods together:
88 $ssh->send("passwd");
89 $ssh->waitfor('password:\s*\z', 1) or die "prompt 'password' not found after 1 second";
90 $ssh->send("curren_password");
91 $ssh->waitfor(':\s*\z', 1) or die "prompt 'New password:' not found";
92 $ssh->send("new_password");
93 $ssh->waitfor(':\s*\z', 1) or die "prompt 'Confirm new password:' not found";
94 $ssh->send("new_password");
95 # check that we have the system prompt again.
97 my ($before_match, $match) = $ssh->waitfor('>\s*\z', 1); # waitfor() in a list context
98 die "passwd failed. passwd said '$before_match'." unless ($match);
99 # closes the ssh connection
101 $ssh->close();
102
104 This module is a wrapper to the ssh executable that is available in
105 your system's $PATH. Use this module to execute commands on the remote
106 SSH server. It authenticates with the user and password you passed in
107 the constructor's attributes "user" and "password".
108 Once an ssh connection was started using the "connect()" method it will
110 remain open until you call the "close()" method. This allows you
111 execute as many commands as you want with the "exec()" method using
112 only one connection. This is a better approach over other ssh wrapper
113 implementations, i.e: Net::SCP, Net::SSH and Net::SCP::Expect, that
114 start a new ssh connection each time a remote command is issued or a
115 file is transfered.
116 It uses Expect.pm module to interact with the SSH server. A
118 "get_expect()" method is provided so you can obtain the internal
119 "Expect" object connected to the SSH server. Use this only if you have
120 some special need that you can't do with the "exec()" method.
121 This module was inspired by Net::SCP::Expect
123 http://search.cpan.org/~djberg/Net-SCP-Expect-0.12/Expect.pm
124 <http://search.cpan.org/~djberg/Net-SCP-Expect-0.12/Expect.pm> and by
125 Net::Telnet and some of its methods work the same as these two modules.
126 IMPORTANT NOTES ABOUT DEALING WITH SSH AND PSEUDO-TERMINALS
128 This module uses Expect to start the local ssh client process, and
129 Expect will interact with this process through a local pseudo-terminal
130 (ptty). Similarly, the ssh client will connect to the SSH server and
131 there will receive an ssh login process attached to a ptty too.
132 During my tests I realized that the I/O to and from the ssh server
134 changes drastically from OS to OS if we let the local and remote pttys
135 configured on their defaults. The echo's and the \r\n translations make
136 a mess that we are never sure what will be sent to the other side and
137 what will be received here.
138 Many ptty features are system dependent and we can't rely on them
140 working the same on different OS's.
141 To avoid these problems I always recommend you to:
143 1) enable the 'raw_pty' constructor attribute. This disables most (if
145 not all) of the problematic features on the local ptty.
146 2) Similarly set the ptty on the remote server to 'raw -echo' as soon
148 as you login. This can be done with:
149 $ssh->exec("stty raw -echo");
151 Obviously your server must support the 'stty' command for that.
153 3) If you won't run on the server interactive commands that prompt for
155 input, like 'passwd', you could prevent the ssh server from attributing
156 a ptty for the ssh login process. This is done by enabling the
157 'no_terminal' constructor attribute. What that does is passing the '-T'
158 option to the ssh client process when it is created. From the BSD ssh
159 client manual:
160 -T Disable pseudo-tty allocation.
161 This will create the cleaner connection possible. You won't have a ptty
163 on the server, and, weirdly, you won't receive a remote prompt. Try
164 yourself 'ssh -T my.ssh.server' to see how it works. Notice that some
165 system commands that rely on a terminal won't work, say, 'who am i',
166 'stty', etc.
167 Also, interactive commands like 'passwd' or 'mail' won't be able to
169 print their prompts.
170 But other system commands will run better: 'ls -l' will be printed
172 without terminal control characters. 'ps -ef' will have the command
173 lines printed fully, since there is no 'columns' terminal limitation.
174 Moral of the story: pseudo terminals do many character translations
176 that can bring some unexpected results in some situations. Avoid them
177 if you can.
178
180 None by default.
181
183 The constructor accepts all the following attributes that can be set in
184 the form of attribute => 'value' pairs. They are presentend in three
185 groups: 1) attributes to configure the ssh client process; 2)
186 attributes to configure the underlying Expect object; 3) attributes to
187 configure this module;
188 ATTRIBUTES TO CONFIGURE THE SSH CLIENT PROCESS
190 Some of the attributes bellow will enable/disable some options of the
191 ssh client. Refer to you ssh client documentation to know what each one
192 does.
193 string binary
195 the complete path to the 'ssh' executable in your machine. The
196 default is 'ssh' what means the ssh used by default is the first
197 one found in your $PATH environment variable.
198 string user
200 the username to login.
201 string password
203 the password used to login. You won't need to set this field if you
204 have public-key authentication configured for you ssh user. Read
205 run_ssh() documentation for more info.
206 string host
208 the address(dns name/ip) to the ssh server
209 string port
211 Feeds the -p ssh client option with alternate ssh port. This option
212 is not set by default.
213 boolean no_terminal
215 If enabled adds the -T ssh client option to the ssh command line.
216 See the discussion on "IMPORTANT NOTES ABOUT DEALING WITH SSH AND
217 PSEUDO-TERMINALS" to know if you want to enable this.
218 char escape_char
220 Passes a character to the -e ssh client option. This enables ssh
221 escapes. Since this option can cause trouble, it is explicitly
222 turned off by default with a '-e none' option being set on the ssh
223 command line.
224 string ssh_option
226 This lets you add your own ssh options to the command line. Set
227 this string to the options you want, like '-v -p 2022', and your
228 options will be added to the ssh command line that will start the
229 ssh process.
230 CONSTRUCTOR OPTIONS THAT CONFIGURE THE INTERNAL EXPECT OBJECT
232 The following constructor attributes can be used to configure special
233 features of the internal Expect object used to communicate with the ssh
234 server. These options will be passed to the Expect object inside the
235 "connect" method before it spawns the ssh process.
236 string log_file
238 Used as argument to the internal Expect->log_file() method. Default
239 is no logfile.
240 boolean log_stdout
242 Used as argument to the internal Expect->log_sdtout() method.
243 Default is 0, to disable log to stdout.
244 boolean exp_internal
246 Argument to be passed to the internal Expect->exp_internal()
247 method. Default is 0, to disable the internal exposure.
248 boolean exp_debug
250 Argument to be passed to the internal Expect->debug() method.
251 Default is 0, to disable debug.
252 boolean raw_pty
254 Argument to be passed to the internal Expect->raw_pty() method.
255 It's recommended that you enable this. See the disscussion in
256 "IMPORTANT NOTES ABOUT DEALING WITH SSH AND PSEUDO-TERMINALS" to
257 know why. Default is 0 to let the local ptty as its defaults.
258 boolean restart_timeout_upon_receive
260 If this is enabled the timeout in all reading operations works as
261 an inactivity timeout - it'll not start counting while there is
262 data arriving on input stream. Default is 0.
263 CONSTRUCTOR OPTIONS TO CONFIGURE THIS MODULE
265 string terminator
266 the line terminator in use on the SSH server, this will added at
267 the end of each command passed to the "exec()" method. The default
268 is "\n".
269 It also affects the read_line() method, it expect each line to be
271 terminated by the 'teminator' character. Lines can also be ended
272 with "\r" or "\r\n" in some systems. Remember to adjust this for
273 your system.
274 You can also use the terminator() method to set this attribute.
276 integer timeout
278 The maximum time to wait for a pattern to show up on input stream
279 before giving up in a read operation. The default is 1 second.
280 Timeout must always be an integer >= 0.
282 This attribute can also be get/set with the "timeout()" method.
284 boolean debug
286 Causes some methods to print debug messages to the STDERR. This
287 feature is not widely implemented yet. (only eat() implements it
288 until this moment)
289
291 boolean run_ssh() - forks the ssh client process
292 # boolean run_ssh() - forks the ssh client process opening an ssh connection to the SSH server.
293 #
294 # This method has three roles:
295 # 1) Instantiate a new Expect object configuring it with all the defaults and user-defined
296 # settings.
297 # 2) Define the ssh command line using the defaults and user-defined settings
298 # 3) Fork the ssh process using the spawn() method of the Expect instance we created.
299 # The SSH connection is established on this step using the user account set in the 'user'
300 # constructor attribute. No password is sent here, that happens only in the login() method.
301 #
302 # This method is run internally by the login() method so you don't need to run it yourself
303 # in most of the cases. You'll run this method alone if you had set up public-key authentication
304 # between the ssh client and the ssh server. In this case you only need to call this method
305 # to have an authenticated ssh connection, you won't call login(). Note that when you
306 # use public-key authentication you won't need to set the 'password' constructor attribute
307 # but you still need to define the 'user' attribute.
308 # If you don't know how to setup public-key authentication there's a good guide at
309 # http://sial.org/howto/openssh/publickey-auth/
310 #
311 # returns:
312 # boolean: 1 if the ssh ran OK or 0 otherwise. In case of failures, use $! to do get info.
313 string login([$login_prompt, $password_prompt] [,$test_success]) -
315 authenticates on the ssh server.
316 # string login ([$login_prompt, $password_prompt] [,$test_success]) - authenticates on the ssh server.
317 # This method responds to the authentication prompt sent by the SSH server.
318 # You can customize the "Login:" and "Password:" prompts that must be expected by passing their
319 # patterns as arguments to this method, although this method has default values that work to most
320 # SSH servers out there.
321 # It runs the run_ssh() method only if it wasn't run before(), but it'll die
322 # if run_ssh() returns false.
323 #
324 # param:
325 # $login_prompt: A pattern string used to match the "Login:" prompt. The default
326 # pattern is qr/ogin:\s*$/
327 #
328 # $password_prompt: A pattern string used to match the "Password:" prompt. The default
329 # pattern is qr/[Pp]assword.*?:|[Pp]assphrase.*?:/
330 #
331 # $test_success: 0 | 1. if 1, login will do an extra-test to verify if the password
332 # entered was accepted. The test consists in verifying if, after sending the password,
333 # the "Password" prompt shows up again what would indicate that the password was rejected.
334 # This test is disabled by default.
335 #
336 # OBS: the number of paramaters passed to this method will tell it what parameters are being passed:
337 # 0 parameters: login() : All the default values will be used.
338 # 1 parameter: login(1) : The $test_success parameter is set.
339 # 2 parameters: login("Login:", "Password:") : the $login_prompt and $password_prompt parameters are set.
340 # 3 parameters: login("Login:", "Password;", 1) : the three parameters received values on this order.
341 #
342 # returns:
343 # string: whatever the SSH server wrote in my input stream after loging in. This usually is some
344 # welcome message and/or the remote prompt. You could use this string to do your verification
345 # that the login was successful. The content returned is removed from the input stream.
346 # dies:
347 # IllegalState: if any of 'host' or 'user' or 'password' fields are unset.
348 # SSHProccessError: if run_ssh() failed to spawn the ssh process
349 # SSHConnectionError: if the connection failed for some reason, like invalid 'host' address or network problems.
350 string exec($cmd [,$timeout]) - executes a command in the remote
352 machine returning its output
353 exec('command') runs 'command' in the remote machine and returns
354 all the output generated by 'command' into a string.
355 boolean waitfor($pattern [,$timeout])
357 # boolean waitfor ($string [, $timeout, $match_type])
358 # This method reads until a pattern or string is found in the input stream.
359 # All the characters before and including the match are removed from the input stream.
360 #
361 # After waitfor returns, use the methods before(), match() and after() to get the data
362 # 'before the match', 'what matched', and 'after the match' respectively.
363 #
364 # If waitfor returns false, whatever content is on input stream can be accessed with
365 # before(). In this case before() will return the same content as peek().
366 #
367 # params:
368 # $string: a string to be matched. It can be a regular expression or a literal string
369 # anb its interpretation as one or other depends on $match_type. Default is
370 # 're', what treats $string as a regular expression.
371 #
372 # $timeout: the timeout in seconds while waiting for $string
373 #
374 # $match_type: match_type affects how $string will be matched:
375 # '-re': means $string is a regular expression.
376 # '-ex': means $string is an "exact match", i.e., will be matched literally.
377 #
378 # returns:
379 # boolean: 1 is returned if string was found, 0 otherwise. When the match fails
380 # waitfor() will only return after waiting $timeout seconds.
381 #
382 # dies:
383 # SSH_CONNECTION_ABORTED if EOF is found (error type 2)
384 # SSH_PROCESS_ERROR if the ssh process has died (error type 3)
385 # SSH_CONNECTION_ERROR if unknown error (type 4) is found
386 string before() - returns the "before match" data of the last waitfor()
388 call.
389 When waitfor() matches, if there is any content before the match,
390 this will be returned by before().
391 If the last waitfor() didn't match, before() will return all the
393 current content on the input stream, just as if you had called
394 peek() with the same timeout.
395 string match() - returns the "match" data of the last waitfor() call,
397 or undef if didn't match.
398 string after() - returns the "after match" data of the last waitfor()
399 call, or undef if didn't match.
400 void close() - terminates the ssh connection
401 void send($string) - sends $string to the SSH server, returns nothing
402 Sends the string to the SSH server. If the ssh server process is
403 attached to a pseudo-terminal (this is the default) it is likely
404 that the echo terminal property will be on, what will make the
405 server place the command you just sent in our input stream, i.e.,
406 you'll see the command you sent in your next read operation.
407 To avoid this, try to disable the echo property on the server-side,
409 using
410 $ssh->exec("stty -echo");
412 It's also advisable to disable the terminal character convertions
414 on server-side, what will make you sure that every character you
415 sent will be received "as-is" to the other side.
416 So you'll probably use this to disable character conversions and
418 echo:
419 $ssh->exec("stty raw -echo");
421 Of course you're server must support the 'stty' command for that
423 work.
424 To guarantee that your characters are not converted by your local
426 pseudo-terminal before you send them out, set the constructor
427 option:
428 raw_pty => 1
430 And if you don't need a terminal on the server-side at all, set the
432 constructor option bellow to 1:
433 no_terminal => 1
435 string peek([$timeout]) - returns what is in the input stream without
437 removing anything
438 # peek([$timeout]) - returns what is in the input stream without removing anything
439 # peek() returns what is available on the input stream until $timeout seconds.
440 # If there is data continuosly arriving on the input stream, subsequent calls to peek()
441 # will return a growing amount of data.
442 #
443 # dies:
444 # SSH_CONNECTION_ABORTED if EOF is found (error type 2)
445 # SSH_PROCESS_ERROR if the ssh process has died (error type 3)
446 # SSH_CONNECTION_ERROR if unknown error (type 4) is found
447 string eat($string) - removes all the head of the input stream until
449 $string inclusive.
450 # string eat($string)- removes all the head of the input stream until $string inclusive.
451 # eat() will only be able to remove the $string if it's currently present on the
452 # input stream because eat() will wait 0 seconds before removing it.
453 #
454 # Use it associated with peek to eat everything that appears on the input stream:
455 #
456 # while ($chunk = $exp->eat($exp->peak())) {
457 # print $chunk;
458 # }
459 #
460 # Or use the read_all() method that does the above loop for you returning the accumulated
461 # result.
462 #
463 # param:
464 # string: a string currently available on the input stream.
465 # If $string doesn't start in the head, all the content before $string will also
466 # be removed.
467 #
468 # If $string is undef or empty string it will be returned immediately as it.
469 #
470 # returns:
471 # string: the removed content or empty string if there is nothing in the input stream.
472 #
473 # dies:
474 # SSH_CONNECTION_ABORTED if EOF is found (error type 2)
475 # SSH_PROCESS_ERROR if the ssh process has died (error type 3)
476 # SSH_CONNECTION_ERROR if unknown error (type 4) is found
477 #
478 # debbuging features:
479 # The following warnings are printed to STDERR if $exp->debug() == 1:
480 # eat() prints a warning is $string wasn't found in the head of the input stream.
481 # eat() prints a warning is $string was empty or undefined.
482 #
483 string read_all([$timeout]) - reads and removes all the output from the
485 input stream.
486 The reading/removing process will be interrupted after $timeout
487 seconds of inactivity on the input stream.
488 string read_line([$timeout]) - reads the next line from the input
490 stream and returns it.
491 # string read_line([$timeout]) - reads the next line from the input stream
492 # Read a line of text. A line is considered to be terminated by the 'teminator'
493 # character. Default is "\n". Lines can also be ended with "\r" or "\r\n".
494 # Remember to adequate this for your system with the terminator() method.
495 # When there are no more lines available, read_line() returns undef. Note that this doen't mean
496 # there is no data left on input stream since there can be a string not terminated with the
497 # 'terminator' character, notably the remote prompt could be left there when read_line() returns
498 # undef.
499 #
500 # params:
501 # $timeout: the timeout waiting for a line. Defaults to timeout().
502 #
503 # returns:
504 # string: a line on the input stream, without the trailing 'terminator' character.
505 # An empty string indicates that the line read only contained the 'terminator'
506 # character (an empty line).
507 # undef: when there are no more lines on the input stream.
508 #
509 void restart_timeout_upon_receive( 0 | 1 ) - changes the timeout
511 counter behaviour
512 # void restart_timeout_upon_receive( 0 | 1 ) - changes the timeout counter behaviour
513 # params:
514 # boolean: if true, sets the timeout to "inactivity timeout", if false
515 # sets it to "absolute timeout".
516 # dies:
517 # IllegalParamenter if argument is not given.
518 Expect get_expect() - returns the internal Expect object
520 params:
521 none
522 returns:
524 an "Expect" object connected to the SSH server. It will die if
525 you try to run it without being connected.
526 dies:
528 IllegalState: if this there is no valid ssh connection
529 established
530
532 Net::SCP::Expect, Net::SCP, Net::SSH::Perl, Expect
533
535 To report bugs please use the bug reporting tool available on CPAN
536 website, in the module's page. That way I can keep track of what I need
537 to do and I can also communicate with you through that tool.
538
540 Bruno Negrao Guimaraes Zica. <bnegrao@cpan.org>.
541
543 Daniel Berger, author of Net::SCP::Expect. Special thanks to the people
544 helping me improve this module by reporting their tests and the bugs
545 they find.
546
548 Copyright (C) 2007 by Bruno Negrao Guimaraes Zica
549 This library is free software; you can redistribute it and/or modify it
551 under the same terms as Perl itself, either Perl version 5.8.3 or, at
552 your option, any later version of Perl 5 you may have available.
553perl v5.12.3 2008-04-23 Net::SSH::Expect(3)