1Net::Telnet(3) User Contributed Perl Documentation Net::Telnet(3)
2
6 Net::Telnet - interact with TELNET port or other TCP ports
7
9 "use Net::Telnet ();"
10 see METHODS or EXAMPLES sections below
12
14 Net::Telnet allows you to make client connections to a TCP port and do
15 network I/O, especially to a port using the TELNET protocol. Simple
16 I/O methods such as print, get, and getline are provided. More
17 sophisticated interactive features are provided because connecting to a
18 TELNET port ultimately means communicating with a program designed for
19 human interaction. These interactive features include the ability to
20 specify a time-out and to wait for patterns to appear in the input
21 stream, such as the prompt from a shell. IPv6 support is available
22 when using perl 5.14 or later, see family().
23 Other reasons to use this module than strictly with a TELNET port are:
25 • You're not familiar with sockets and you want a simple way to make
27 client connections to TCP services.
28 • You want to be able to specify your own time-out while connecting,
30 reading, or writing.
31 • You're communicating with an interactive program at the other end of
33 some socket or pipe and you want to wait for certain patterns to
34 appear.
35 Here's an example that prints who's logged-on to a remote host. In
37 addition to a username and password, you must also know the user's
38 shell prompt, which for this example is "bash$ "
39 use Net::Telnet ();
41 $t = new Net::Telnet (Timeout => 10,
42 Prompt => '/bash\$ $/');
43 $t->open($host);
44 $t->login($username, $passwd);
45 @lines = $t->cmd("who");
46 print @lines;
47 See the EXAMPLES section below for more examples.
49 Usage questions should be directed to the perlmonks.org discussion
51 group. Bugs can be viewed or reported at cpan.org on the Net::Telnet
52 page.
53 What To Know Before Using
55 • All output is flushed while all input is buffered. Each object
56 contains its own input buffer.
57 • The output record separator for print() and cmd() is set to "\n" by
59 default, so that you don't have to append all your commands with a
60 newline. To avoid printing a trailing "\n" use put() or set the
61 output_record_separator to "".
62 • The methods login() and cmd() use the prompt setting in the object to
64 determine when a login or remote command is complete. Those methods
65 will fail with a time-out if you don't set the prompt correctly.
66 • Use a combination of print() and waitfor() as an alternative to
68 login() or cmd() when they don't do what you want.
69 • Errors such as timing-out are handled according to the error mode
71 action. The default action is to print an error message to standard
72 error and have the program die. See the errmode() method for more
73 information.
74 • When constructing the match operator argument for prompt() or
76 waitfor(), always use single quotes instead of double quotes to avoid
77 unexpected backslash interpretation (e.g. '/bash\$ $/'). If you're
78 constructing a DOS like file path, you'll need to use four
79 backslashes to represent one (e.g. '/c:\\\\users\\\\bill>$/i').
80 Of course don't forget about regexp metacharacters like ".", "[", or
82 "$". You'll only need a single backslash to quote them. The anchor
83 metacharacters "^" and "$" refer to positions in the input buffer.
84 To avoid matching characters read that look like a prompt, it's a
85 good idea to end your prompt pattern with the "$" anchor. That way
86 the prompt will only match if it's the last thing read.
87 • In the input stream, each sequence of carriage return and line feed
89 (i.e. "\015\012" or CR LF) is converted to "\n". In the output
90 stream, each occurrence of "\n" is converted to a sequence of CR LF.
91 See binmode() to change the behavior. TCP protocols typically use
92 the ASCII sequence, carriage return and line feed to designate a
93 newline.
94 • Timing-out while making a connection is disabled for machines that
96 don't support the alarm() function. Most notably these include MS-
97 Windows machines.
98 • You'll need to be running at least Perl version 5.002 to use this
100 module. This module does not require any libraries that don't
101 already come with a standard Perl distribution.
102 If you have the IO:: libraries installed (they come standard with
104 perl5.004 and later) then IO::Socket::INET is used as a base class,
105 otherwise FileHandle is used.
106 Debugging
108 The typical usage bug causes a time-out error because you've made
109 incorrect assumptions about what the remote side actually sends. The
110 easiest way to reconcile what the remote side sends with your
111 expectations is to use input_log() or dump_log().
112 dump_log() allows you to see the data being sent from the remote side
114 before any translation is done, while input_log() shows you the results
115 after translation. The translation includes converting end of line
116 characters, removing and responding to TELNET protocol commands in the
117 data stream.
118 Style of Named Parameters
120 Two different styles of named parameters are supported. This document
121 only shows the IO:: style:
122 Net::Telnet->new(Timeout => 20);
124 however the dash-option style is also allowed:
126 Net::Telnet->new(-timeout => 20);
128 Connecting to a Remote MS-Windows Machine
130 By default MS-Windows doesn't come with a TELNET server. However third
131 party TELNET servers are available. Unfortunately many of these
132 servers falsely claim to be a TELNET server. This is especially true
133 of the so-called "Microsoft Telnet Server" that comes installed with
134 some newer versions MS-Windows.
135 When a TELNET server first accepts a connection, it must use the ASCII
137 control characters carriage-return and line-feed to start a new line
138 (see RFC854). A server like the "Microsoft Telnet Server" that doesn't
139 do this, isn't a TELNET server. These servers send ANSI terminal
140 escape sequences to position to a column on a subsequent line and to
141 even position while writing characters that are adjacent to each other.
142 Worse, when sending output these servers resend previously sent command
143 output in a misguided attempt to display an entire terminal screen.
144 Connecting Net::Telnet to one of these false TELNET servers makes your
146 job of parsing command output very difficult. It's better to replace a
147 false TELNET server with a real TELNET server. The better TELNET
148 servers for MS-Windows allow you to avoid the ANSI escapes by turning
149 off something some of them call console mode.
150
152 In the calling sequences below, square brackets [] represent optional
153 parameters.
154 new - create a new Net::Telnet object
156 $obj = new Net::Telnet ([$host]);
157 $obj = new Net::Telnet ([Binmode => $mode,]
159 [Cmd_remove_mode => $mode,]
160 [Dump_Log => $filename,]
161 [Errmode => $errmode,]
162 [Family => $family,]
163 [Fhopen => $filehandle,]
164 [Host => $host,]
165 [Input_log => $file,]
166 [Input_record_separator => $chars,]
167 [Localfamily => $family,]
168 [Localhost => $host,]
169 [Max_buffer_length => $len,]
170 [Ofs => $chars,]
171 [Option_log => $file,]
172 [Ors => $chars,]
173 [Output_field_separator => $chars,]
174 [Output_log => $file,]
175 [Output_record_separator => $chars,]
176 [Port => $port,]
177 [Prompt => $matchop,]
178 [Rs => $chars,]
179 [Telnetmode => $mode,]
180 [Timeout => $secs,]);
181 This is the constructor for Net::Telnet objects. A new object is
183 returned on success, the error mode action is performed on failure
184 - see errmode(). The optional arguments are short-cuts to methods
185 of the same name.
186 If the $host argument is given then the object is opened by
188 connecting to TCP $port on $host. Also see open(). The new object
189 returned is given the following defaults in the absence of
190 corresponding named parameters:
191 • The default Host is "localhost"
193 • The default Port is 23
195 • The default Family is "ipv4"
197 • The default Prompt is '/[\$%#>] $/'
199 • The default Timeout is 10
201 • The default Errmode is "die"
203 • The default Output_record_separator is "\n". Note that Ors is
205 synonymous with Output_record_separator.
206 • The default Input_record_separator is "\n". Note that Rs is
208 synonymous with Input_record_separator.
209 • The default Binmode is 0, which means do newline translation.
211 • The default Telnetmode is 1, which means respond to TELNET
213 commands in the data stream.
214 • The default Cmd_remove_mode is "auto"
216 • The defaults for Dump_log, Input_log, Option_log, and
218 Output_log are "", which means that logging is turned-off.
219 • The default Max_buffer_length is 1048576 bytes, i.e. 1 MiB.
221 • The default Output_field_separator is "". Note that Ofs is
223 synonymous with Output_field_separator.
224 • The default Localhost is ""
226 • The default Localfamily is "ipv4"
228 binmode - toggle newline translation
230 $mode = $obj->binmode;
231 $prev = $obj->binmode($mode);
233 This method controls whether or not sequences of carriage returns
235 and line feeds (CR LF or more specifically "\015\012") are
236 translated. By default they are translated (i.e. binmode is 0).
237 If no argument is given, the current mode is returned.
239 If $mode is 1 then binmode is on and newline translation is not
241 done.
242 If $mode is 0 then binmode is off and newline translation is done.
244 In the input stream, each sequence of CR LF is converted to "\n"
245 and in the output stream, each occurrence of "\n" is converted to a
246 sequence of CR LF.
247 Note that input is always buffered. Changing binmode doesn't
249 effect what's already been read into the buffer. Output is not
250 buffered and changing binmode will have an immediate effect.
251 break - send TELNET break character
253 $ok = $obj->break;
254 This method sends the TELNET break character. This character is
256 provided because it's a signal outside the ASCII character set
257 which is currently given local meaning within many systems. It's
258 intended to indicate that the Break Key or the Attention Key was
259 hit.
260 This method returns 1 on success, or performs the error mode action
262 on failure.
263 buffer - scalar reference to object's input buffer
265 $ref = $obj->buffer;
266 This method returns a scalar reference to the input buffer for
268 $obj. Data in the input buffer is data that has been read from the
269 remote side but has yet to be read by the user. Modifications to
270 the input buffer are returned by a subsequent read.
271 buffer_empty - discard all data in object's input buffer
273 $obj->buffer_empty;
274 This method removes all data in the input buffer for $obj.
276 close - close object
278 $ok = $obj->close;
279 This method closes the socket, file, or pipe associated with the
281 object. It always returns a value of 1.
282 cmd - issue command and retrieve output
284 $ok = $obj->cmd($string);
285 $ok = $obj->cmd(String => $string,
286 [Output => $ref,]
287 [Cmd_remove_mode => $mode,]
288 [Errmode => $mode,]
289 [Input_record_separator => $chars,]
290 [Ors => $chars,]
291 [Output_record_separator => $chars,]
292 [Prompt => $match,]
293 [Rs => $chars,]
294 [Timeout => $secs,]);
295 @output = $obj->cmd($string);
297 @output = $obj->cmd(String => $string,
298 [Output => $ref,]
299 [Cmd_remove_mode => $mode,]
300 [Errmode => $mode,]
301 [Input_record_separator => $chars,]
302 [Ors => $chars,]
303 [Output_record_separator => $chars,]
304 [Prompt => $match,]
305 [Rs => $chars,]
306 [Timeout => $secs,]);
307 This method sends the command $string, and reads the characters
309 sent back by the command up until and including the matching
310 prompt. It's assumed that the program to which you're sending is
311 some kind of command prompting interpreter such as a shell.
312 The command $string is automatically appended with the
314 output_record_separator, by default it is "\n". This is similar to
315 someone typing a command and hitting the return key. Set the
316 output_record_separator to change this behavior.
317 In a scalar context, the characters read from the remote side are
319 discarded and 1 is returned on success. On time-out, eof, or other
320 failures, the error mode action is performed. See errmode().
321 In a list context, just the output generated by the command is
323 returned, one line per element. In other words, all the characters
324 in between the echoed back command string and the prompt are
325 returned. If the command happens to return no output, a list
326 containing one element, the empty string is returned. This is so
327 the list will indicate true in a boolean context. On time-out,
328 eof, or other failures, the error mode action is performed. See
329 errmode().
330 The characters that matched the prompt may be retrieved using
332 last_prompt().
333 Many command interpreters echo back the command sent. In most
335 situations, this method removes the first line returned from the
336 remote side (i.e. the echoed back command). See cmd_remove_mode()
337 for more control over this feature.
338 Use dump_log() to debug when this method keeps timing-out and you
340 don't think it should.
341 Consider using a combination of print() and waitfor() as an
343 alternative to this method when it doesn't do what you want, e.g.
344 the command you send prompts for input.
345 The Output named parameter provides an alternative method of
347 receiving command output. If you pass a scalar reference, all the
348 output (even if it contains multiple lines) is returned in the
349 referenced scalar. If you pass an array or hash reference, the
350 lines of output are returned in the referenced array or hash. You
351 can use input_record_separator() to change the notion of what
352 separates a line.
353 Optional named parameters are provided to override the current
355 settings of cmd_remove_mode, errmode, input_record_separator, ors,
356 output_record_separator, prompt, rs, and timeout. Rs is synonymous
357 with input_record_separator and ors is synonymous with
358 output_record_separator.
359 cmd_remove_mode - toggle removal of echoed commands
361 $mode = $obj->cmd_remove_mode;
362 $prev = $obj->cmd_remove_mode($mode);
364 This method controls how to deal with echoed back commands in the
366 output returned by cmd(). Typically, when you send a command to
367 the remote side, the first line of output returned is the command
368 echoed back. Use this mode to remove the first line of output
369 normally returned by cmd().
370 If no argument is given, the current mode is returned.
372 If $mode is 0 then the command output returned from cmd() has no
374 lines removed. If $mode is a positive integer, then the first
375 $mode lines of command output are stripped.
376 By default, $mode is set to "auto". Auto means that whether or not
378 the first line of command output is stripped, depends on whether or
379 not the remote side offered to echo. By default, Net::Telnet
380 always accepts an offer to echo by the remote side. You can change
381 the default to reject such an offer using option_accept().
382 A warning is printed to STDERR when attempting to set this
384 attribute to something that is not "auto" or a non-negative
385 integer.
386 dump_log - log all I/O in dump format
388 $fh = $obj->dump_log;
389 $fh = $obj->dump_log($fh);
391 $fh = $obj->dump_log($tiefh);
393 $fh = $obj->dump_log($filename);
395 This method starts or stops dump format logging of all the object's
397 input and output. The dump format shows the blocks read and
398 written in a hexadecimal and printable character format. This
399 method is useful when debugging, however you might want to first
400 try input_log() as it's more readable.
401 If no argument is given, the log filehandle is returned. A
403 returned empty string indicates logging is off.
404 To stop logging, use an empty string as an argument. The stopped
406 filehandle is not closed.
407 If an open filehandle is given, it is used for logging and
409 returned. Otherwise, the argument is assumed to be the name of a
410 file, the filename is opened for logging and a filehandle to it is
411 returned. If the filehandle is not already opened or the filename
412 can't be opened for writing, the error mode action is performed.
413 The filehandle can be a tied filehandle.
414 eof - end of file indicator
416 $eof = $obj->eof;
417 This method returns 1 if end of file has been read, otherwise it
419 returns an empty string. Because the input is buffered this isn't
420 the same thing as $obj has closed. In other words $obj can be
421 closed but there still can be stuff in the buffer to be read.
422 Under this condition you can still read but you won't be able to
423 write.
424 errmode - define action to be performed on error
426 $mode = $obj->errmode;
427 $prev = $obj->errmode($mode);
429 This method gets or sets the action used when errors are
431 encountered using the object. The first calling sequence returns
432 the current error mode. The second calling sequence sets it to
433 $mode and returns the previous mode. Valid values for $mode are
434 "die" (the default), "return", a coderef, or an arrayref.
435 When mode is "die" and an error is encountered using the object,
437 then an error message is printed to standard error and the program
438 dies.
439 When mode is "return" then the method generating the error places
441 an error message in the object and returns an undefined value in a
442 scalar context and an empty list in list context. The error
443 message may be obtained using errmsg().
444 When mode is a coderef, then when an error is encountered coderef
446 is called with the error message as its first argument. Using this
447 mode you may have your own subroutine handle errors. If coderef
448 itself returns then the method generating the error returns
449 undefined or an empty list depending on context.
450 When mode is an arrayref, the first element of the array must be a
452 coderef. Any elements that follow are the arguments to coderef.
453 When an error is encountered, the coderef is called with its
454 arguments. Using this mode you may have your own subroutine handle
455 errors. If the coderef itself returns then the method generating
456 the error returns undefined or an empty list depending on context.
457 A warning is printed to STDERR when attempting to set this
459 attribute to something that is not "die", "return", a coderef, or
460 an arrayref whose first element isn't a coderef.
461 errmsg - most recent error message
463 $msg = $obj->errmsg;
464 $prev = $obj->errmsg(@msgs);
466 The first calling sequence returns the error message associated
468 with the object. The empty string is returned if no error has been
469 encountered yet. The second calling sequence sets the error
470 message for the object to the concatenation of @msgs and returns
471 the previous error message. Normally, error messages are set
472 internally by a method when an error is encountered.
473 error - perform the error mode action
475 $obj->error(@msgs);
476 This method concatenates @msgs into a string and places it in the
478 object as the error message. Also see errmsg(). It then performs
479 the error mode action. Also see errmode().
480 If the error mode doesn't cause the program to die, then an
482 undefined value or an empty list is returned depending on the
483 context.
484 This method is primarily used by this class or a sub-class to
486 perform the user requested action when an error is encountered.
487 family - IP address family for remote host
489 $family = $obj->family;
490 $prev = $obj->family($family);
492 This method designates which IP address family host() refers to,
494 i.e. IPv4 or IPv6. IPv6 support is available when using perl 5.14
495 or later. With no argument it returns the current value set in the
496 object. With an argument it sets the current address family to
497 $family and returns the previous address family. Valid values are
498 "ipv4", "ipv6", or "any". When "any", the host() can be a hostname
499 or IP address for either IPv4 or IPv6. After connecting, you can
500 use sockfamily() to determine which IP address family was used.
501 The default value is "ipv4".
503 The error mode action is performed when attempting to set this
505 attribute to something that isn't "ipv4", "ipv6", or "any". It is
506 also performed when attempting to set it to "ipv6" when the Socket
507 module is less than version 1.94 or IPv6 is not supported in the OS
508 as indicated by Socket::AF_INET6 not being defined.
509 fhopen - use already open filehandle for I/O
511 $ok = $obj->fhopen($fh);
512 This method associates the open filehandle $fh with $obj for
514 further I/O. Filehandle $fh must already be opened.
515 Suppose you want to use the features of this module to do I/O to
517 something other than a TCP port, for example STDIN or a filehandle
518 opened to read from a process. Instead of opening the object for
519 I/O to a TCP port by using open() or new(), call this method
520 instead.
521 The value 1 is returned success, the error mode action is performed
523 on failure.
524 get - read block of data
526 $data = $obj->get([Binmode => $mode,]
527 [Errmode => $errmode,]
528 [Telnetmode => $mode,]
529 [Timeout => $secs,]);
530 This method reads a block of data from the object and returns it
532 along with any buffered data. If no buffered data is available to
533 return, it will wait for data to read using the timeout specified
534 in the object. You can override that timeout using $secs. Also
535 see timeout(). If buffered data is available to return, it also
536 checks for a block of data that can be immediately read.
537 On eof an undefined value is returned. On time-out or other
539 failures, the error mode action is performed. To distinguish
540 between eof or an error occurring when the error mode is not set to
541 "die", use eof().
542 Optional named parameters are provided to override the current
544 settings of binmode, errmode, telnetmode, and timeout.
545 getline - read next line
547 $line = $obj->getline([Binmode => $mode,]
548 [Errmode => $errmode,]
549 [Input_record_separator => $chars,]
550 [Rs => $chars,]
551 [Telnetmode => $mode,]
552 [Timeout => $secs,]);
553 This method reads and returns the next line of data from the
555 object. You can use input_record_separator() to change the notion
556 of what separates a line. The default is "\n". If a line isn't
557 immediately available, this method blocks waiting for a line or a
558 time-out.
559 On eof an undefined value is returned. On time-out or other
561 failures, the error mode action is performed. To distinguish
562 between eof or an error occurring when the error mode is not set to
563 "die", use eof().
564 Optional named parameters are provided to override the current
566 settings of binmode, errmode, input_record_separator, rs,
567 telnetmode, and timeout. Rs is synonymous with
568 input_record_separator.
569 getlines - read next lines
571 @lines = $obj->getlines([Binmode => $mode,]
572 [Errmode => $errmode,]
573 [Input_record_separator => $chars,]
574 [Rs => $chars,]
575 [Telnetmode => $mode,]
576 [Timeout => $secs,]
577 [All => $boolean,]);
578 This method reads and returns all the lines of data from the object
580 until end of file is read. You can use input_record_separator() to
581 change the notion of what separates a line. The default is "\n".
582 A time-out error occurs if all the lines can't be read within the
583 time-out interval. See timeout().
584 The behavior of this method was changed in version 3.03. Prior to
586 version 3.03 this method returned just the lines available from the
587 next read. To get that old behavior, use the optional named
588 parameter All and set $boolean to "" or 0.
589 If only eof is read then an empty list is returned. On time-out or
591 other failures, the error mode action is performed. Use eof() to
592 distinguish between reading only eof or an error occurring when the
593 error mode is not set to "die".
594 Optional named parameters are provided to override the current
596 settings of binmode, errmode, input_record_separator, rs,
597 telnetmode, and timeout. Rs is synonymous with
598 input_record_separator.
599 host - name or IP address of remote host
601 $host = $obj->host;
602 $prev = $obj->host($host);
604 This method designates the remote host for open(). It is either a
606 hostname or an IP address. With no argument it returns the current
607 value set in the object. With an argument it sets the current host
608 name to $host and returns the previous value. Use family() to
609 control which IP address family, IPv4 or IPv6, host refers to.
610 The default value is "localhost". It may also be set by open() or
612 new().
613 input_log - log all input
615 $fh = $obj->input_log;
616 $fh = $obj->input_log($fh);
618 $fh = $obj->input_log($tiefh);
620 $fh = $obj->input_log($filename);
622 This method starts or stops logging of input. This is useful when
624 debugging. Also see dump_log(). Because most command interpreters
625 echo back commands received, it's likely all your output will also
626 be in this log. Note that input logging occurs after newline
627 translation. See binmode() for details on newline translation.
628 If no argument is given, the log filehandle is returned. A
630 returned empty string indicates logging is off.
631 To stop logging, use an empty string as an argument. The stopped
633 filehandle is not closed.
634 If an open filehandle is given, it is used for logging and
636 returned. Otherwise, the argument is assumed to be the name of a
637 file, the filename is opened for logging and a filehandle to it is
638 returned. If the filehandle is not already opened or the filename
639 can't be opened for writing, the error mode action is performed.
640 The filehandle can be a tied filehandle.
641 input_record_separator - input line delimiter
643 $chars = $obj->input_record_separator;
644 $prev = $obj->input_record_separator($chars);
646 This method designates the line delimiter for input. It's used
648 with getline(), getlines(), and cmd() to determine lines in the
649 input.
650 With no argument this method returns the current input record
652 separator set in the object. With an argument it sets the input
653 record separator to $chars and returns the previous value. Note
654 that $chars must have length.
655 A warning is printed to STDERR when attempting to set this
657 attribute to a string with no length.
658 last_prompt - last prompt read
660 $string = $obj->last_prompt;
661 $prev = $obj->last_prompt($string);
663 With no argument this method returns the last prompt read by cmd()
665 or login(). See prompt(). With an argument it sets the last
666 prompt read to $string and returns the previous value. Normally,
667 only internal methods set the last prompt.
668 lastline - last line read
670 $line = $obj->lastline;
671 $prev = $obj->lastline($line);
673 This method retrieves the last line read from the object. This may
675 be a useful error message when the remote side abnormally closes
676 the connection. Typically the remote side will print an error
677 message before closing.
678 With no argument this method returns the last line read from the
680 object. With an argument it sets the last line read to $line and
681 returns the previous value. Normally, only internal methods set
682 the last line.
683 localfamily - IP address family for local host
685 $localfamily = $obj->localfamily;
686 $prev = $obj->localfamily($family);
688 This method designates which IP address family localhost() refers
690 to, i.e. IPv4 or IPv6. IPv6 support is available when using perl
691 5.14 or later. With no argument it returns the current value set
692 in the object. With an argument it sets the current local address
693 family to $family and returns the previous address family. Valid
694 values are "ipv4", "ipv6", or "any". When "any", the localhost()
695 can be a hostname or IP address for either IPv4 or IPv6.
696 The default value is "ipv4".
698 The error mode action is performed when attempting to set this
700 attribute to something that isn't "ipv4", "ipv6", or "any". It is
701 also performed when attempting to set it to "ipv6" when the Socket
702 module is less than version 1.94 or IPv6 is not supported in the OS
703 as indicated by Socket::AF_INET6 not being defined.
704 localhost - bind local socket to a specific network interface
706 $localhost = $obj->localhost;
707 $prev = $obj->localhost($host);
709 This method designates the local socket IP address for open(). It
711 is either a hostname, an IP address, or a null string (i.e. ""). A
712 null string disables this feature.
713 Normally the OS picks which local network interface to use. This
715 method is useful when the local machine has more than one network
716 interface and you want to bind to a specific one. With no argument
717 it returns the current value set in the object. With an argument
718 it sets the current local host name to $host and returns the
719 previous value. Use localfamily() to control which IP address
720 family, IPv4 or IPv6, local host refers to.
721 The default value is "".
723 login - perform standard login
725 $ok = $obj->login($username, $password);
726 $ok = $obj->login(Name => $username,
728 Password => $password,
729 [Errmode => $mode,]
730 [Prompt => $match,]
731 [Timeout => $secs,]);
732 This method performs a standard login by waiting for a login prompt
734 and responding with $username, then waiting for the password prompt
735 and responding with $password, and then waiting for the command
736 interpreter prompt. If any of those prompts sent by the remote
737 side don't match what's expected, this method will time-out, unless
738 timeout is turned off.
739 Login prompt must match either of these case insensitive patterns:
741 /login[: ]*$/i
743 /username[: ]*$/i
744 Password prompt must match this case insensitive pattern:
746 /password[: ]*$/i
748 The command interpreter prompt must match the current setting of
750 prompt. See prompt().
751 Use dump_log() to debug when this method keeps timing-out and you
753 don't think it should.
754 Consider using a combination of print() and waitfor() as an
756 alternative to this method when it doesn't do what you want, e.g.
757 the remote host doesn't prompt for a username.
758 On success, 1 is returned. On time out, eof, or other failures,
760 the error mode action is performed. See errmode().
761 Optional named parameters are provided to override the current
763 settings of errmode, prompt, and timeout.
764 max_buffer_length - maximum size of input buffer
766 $len = $obj->max_buffer_length;
767 $prev = $obj->max_buffer_length($len);
769 This method designates the maximum size of the input buffer. An
771 error is generated when a read causes the buffer to exceed this
772 limit. The default value is 1,048,576 bytes (1 MiB). The input
773 buffer can grow much larger than the block size when you
774 continuously read using getline() or waitfor() and the data stream
775 contains no newlines or matching waitfor patterns.
776 With no argument, this method returns the current maximum buffer
778 length set in the object. With an argument it sets the maximum
779 buffer length to $len and returns the previous value. Values of
780 $len smaller than 512 will be adjusted to 512.
781 A warning is printed to STDERR when attempting to set this
783 attribute to something that isn't a positive integer.
784 ofs - field separator for print
786 $chars = $obj->ofs
787 $prev = $obj->ofs($chars);
789 This method is synonymous with output_field_separator().
791 open - connect to port on remote host
793 $ok = $obj->open($host);
794 $ok = $obj->open([Host => $host,]
796 [Port => $port,]
797 [Family => $family,]
798 [Errmode => $mode,]
799 [Timeout => $secs,]
800 [Localhost => $host,]
801 [Localfamily => $family,]);
802 This method opens a TCP connection to $port on $host for the IP
804 address $family. If any of those arguments are missing then the
805 current attribute value for the object is used. Specifying Host
806 sets that attribute for the object. Specifying any of the other
807 optional named parameters overrides the current setting.
808 The default IP address family is "ipv4". $family may be set to
810 "ipv4", "ipv6", or "any". See family() for more details.
811 Localhost is used to bind to a specific local network interface.
813 If the object is already open, it is closed before attempting a
815 connection.
816 On success 1 is returned. On time-out or other connection
818 failures, the error mode action is performed. See errmode().
819 Time-outs don't work for this method on machines that don't
821 implement SIGALRM - most notably MS-Windows machines. For those
822 machines, an error is returned when the system reaches its own
823 time-out while trying to connect.
824 A side effect of this method is to reset the alarm interval
826 associated with SIGALRM.
827 option_accept - indicate willingness to accept a TELNET option
829 $fh = $obj->option_accept([Do => $telopt,]
830 [Dont => $telopt,]
831 [Will => $telopt,]
832 [Wont => $telopt,]);
833 This method is used to indicate whether to accept or reject an
835 offer to enable a TELNET option made by the remote side. If you're
836 using Do or Will to indicate a willingness to enable, then a
837 notification callback must have already been defined by a prior
838 call to option_callback(). See option_callback() for details on
839 receiving enable/disable notification of a TELNET option.
840 You can give multiple Do, Dont, Will, or Wont arguments for
842 different TELNET options in the same call to this method.
843 The following example describes the meaning of the named
845 parameters. A TELNET option, such as "TELOPT_ECHO" used below, is
846 an integer constant that you can import from Net::Telnet. See the
847 source in file Telnet.pm for the complete list.
848 • Do => "TELOPT_ECHO"
850 • we'll accept an offer to enable the echo option on the
852 local side
853 • Dont => "TELOPT_ECHO"
855 • we'll reject an offer to enable the echo option on the
857 local side
858 • Will => "TELOPT_ECHO"
860 • we'll accept an offer to enable the echo option on the
862 remote side
863 • Wont => "TELOPT_ECHO"
865 • we'll reject an offer to enable the echo option on the
867 remote side
868 • Use option_send() to send a request to the remote side to
870 enable or disable a particular TELNET option.
871 option_callback - define the option negotiation callback
873 $coderef = $obj->option_callback;
874 $prev = $obj->option_callback($coderef);
876 This method defines the callback subroutine that is called when a
878 TELNET option is enabled or disabled. Once defined, the
879 option_callback may not be undefined. However, calling this method
880 with a different $coderef changes it.
881 A warning is printed to STDERR when attempting to set this
883 attribute to something that isn't a coderef.
884 Here are the circumstances that invoke $coderef:
886 • An option becomes enabled because the remote side requested an
888 enable and option_accept() had been used to arrange that it be
889 accepted.
890 • The remote side arbitrarily decides to disable an option that
892 is currently enabled. Note that Net::Telnet always accepts a
893 request to disable from the remote side.
894 • option_send() was used to send a request to enable or disable
896 an option and the response from the remote side has just been
897 received. Note, that if a request to enable is rejected then
898 $coderef is still invoked even though the option didn't change.
899 • Here are the arguments passed to &$coderef:
901 &$coderef($obj, $option, $is_remote,
903 $is_enabled, $was_enabled, $buf_position);
904 • 1. $obj is the Net::Telnet object
906 • 2. $option is the TELNET option. Net::Telnet exports
908 constants for the various TELNET options which just equate to
909 an integer.
910 • 3. $is_remote is a boolean indicating for which side the
912 option applies.
913 • 4. $is_enabled is a boolean indicating the option is enabled
915 or disabled
916 • 5. $was_enabled is a boolean indicating the option was
918 previously enabled or disabled
919 • 6. $buf_position is an integer indicating the position in the
921 object's input buffer where the option takes effect. See
922 buffer() to access the object's input buffer.
923 option_log - log all TELNET options sent or received
925 $fh = $obj->option_log;
926 $fh = $obj->option_log($fh);
928 $fh = $obj->option_log($tiefh);
930 $fh = $obj->option_log($filename);
932 This method starts or stops logging of all TELNET options being
934 sent or received. This is useful for debugging when you send
935 options via option_send() or you arrange to accept option requests
936 from the remote side via option_accept(). Also see dump_log().
937 If no argument is given, the log filehandle is returned. An empty
939 string indicates logging is off.
940 To stop logging, use an empty string as an argument. The stopped
942 filehandle is not closed.
943 If an open filehandle is given, it is used for logging and
945 returned. Otherwise, the argument is assumed to be the name of a
946 file, the filename is opened for logging and a filehandle to it is
947 returned. If the filehandle is not already opened or the filename
948 can't be opened for writing, the error mode action is performed.
949 The filehandle can be a tied filehandle.
950 option_send - send TELNET option negotiation request
952 $ok = $obj->option_send([Do => $telopt,]
953 [Dont => $telopt,]
954 [Will => $telopt,]
955 [Wont => $telopt,]
956 [Async => $boolean,]);
957 This method is not yet implemented. Look for it in a future
959 version.
960 option_state - get current state of a TELNET option
962 $hashref = $obj->option_state($telopt);
963 This method returns a hashref containing a copy of the current
965 state of TELNET option $telopt.
966 Here are the values returned in the hash:
968 • $hashref->{remote_enabled}
970 • boolean that indicates if the option is enabled on the
972 remote side.
973 • $hashref->{remote_enable_ok}
975 • boolean that indicates if it's ok to accept an offer to
977 enable this option on the remote side.
978 • $hashref->{remote_state}
980 • string used to hold the internal state of option
982 negotiation for this option on the remote side.
983 • $hashref->{local_enabled}
985 • boolean that indicates if the option is enabled on the
987 local side.
988 • $hashref->{local_enable_ok}
990 • boolean that indicates if it's ok to accept an offer to
992 enable this option on the local side.
993 • $hashref->{local_state}
995 • string used to hold the internal state of option
997 negotiation for this option on the local side.
998 ors - output line delimiter
1000 $chars = $obj->ors;
1001 $prev = $obj->ors($chars);
1003 This method is synonymous with output_record_separator().
1005 output_field_separator - field separator for print
1007 $chars = $obj->output_field_separator;
1008 $prev = $obj->output_field_separator($chars);
1010 This method designates the output field separator for print().
1012 Ordinarily the print method simply prints out the comma separated
1013 fields you specify. Set this to specify what's printed between
1014 fields.
1015 With no argument this method returns the current output field
1017 separator set in the object. With an argument it sets the output
1018 field separator to $chars and returns the previous value.
1019 By default it's set to an empty string.
1021 output_log - log all output
1023 $fh = $obj->output_log;
1024 $fh = $obj->output_log($fh);
1026 $fh = $obj->output_log($tiefh);
1028 $fh = $obj->output_log($filename);
1030 This method starts or stops logging of output. This is useful when
1032 debugging. Also see dump_log(). Because most command interpreters
1033 echo back commands received, it's likely all your output would also
1034 be in an input log. See input_log(). Note that output logging
1035 occurs before newline translation. See binmode() for details on
1036 newline translation.
1037 If no argument is given, the log filehandle is returned. A
1039 returned empty string indicates logging is off.
1040 To stop logging, use an empty string as an argument. The stopped
1042 filehandle is not closed.
1043 If an open filehandle is given, it is used for logging and
1045 returned. Otherwise, the argument is assumed to be the name of a
1046 file, the filename is opened for logging and a filehandle to it is
1047 returned. If the filehandle is not already opened or the filename
1048 can't be opened for writing, the error mode action is performed.
1049 The filehandle can be a tied filehandle.
1050 output_record_separator - output line delimiter
1052 $chars = $obj->output_record_separator;
1053 $prev = $obj->output_record_separator($chars);
1055 This method designates the output line delimiter for print() and
1057 cmd(). Set this to specify what's printed at the end of print()
1058 and cmd().
1059 The output record separator is set to "\n" by default, so there's
1061 no need to append all your commands with a newline. To avoid
1062 printing the output_record_separator use put() or set the
1063 output_record_separator to an empty string.
1064 With no argument this method returns the current output record
1066 separator set in the object. With an argument it sets the output
1067 record separator to $chars and returns the previous value.
1068 peerhost - IP address of the other end of the socket connection
1070 $ipaddr = $obj->peerhost;
1071 This method returns a string which is the IPv4 or IPv6 address the
1073 remote socket is bound to (i.e. it is the IP address of host()).
1074 It returns "" when not connected.
1075 peerport - TCP port of the other end of the socket connection
1077 $port = $obj->peerport;
1078 This method returns the port number which the remote socket is
1080 bound to. It is the same as the port() number when connected. It
1081 returns "" when not connected.
1082 port - remote port
1084 $port = $obj->port;
1085 $prev = $obj->port($port);
1087 This method designates the remote TCP port for open(). With no
1089 argument this method returns the current port number. With an
1090 argument it sets the current port number to $port and returns the
1091 previous port. If $port is a TCP service name, then it's first
1092 converted to a port number using the perl function getservbyname().
1093 The default value is 23.
1095 The error mode action is performed when attempting to set this
1097 attribute to something that is not a positive integer or a valid
1098 TCP service name.
1099 print - write to object
1101 $ok = $obj->print(@list);
1102 This method writes @list followed by the output_record_separator to
1104 the open object and returns 1 if all data was successfully written.
1105 On time-out or other failures, the error mode action is performed.
1106 See errmode().
1107 By default, the output_record_separator() is set to "\n" so all
1109 your commands automatically end with a newline. In most cases your
1110 output is being read by a command interpreter which won't accept a
1111 command until newline is read. This is similar to someone typing a
1112 command and hitting the return key. To avoid printing a trailing
1113 "\n" use put() instead or set the output_record_separator to an
1114 empty string.
1115 On failure, it's possible that some data was written. If you
1117 choose to try and recover from a print timing-out, use
1118 print_length() to determine how much was written before the error
1119 occurred.
1120 You may also use the output field separator to print a string
1122 between the list elements. See output_field_separator().
1123 print_length - number of bytes written by print
1125 $num = $obj->print_length;
1126 This returns the number of bytes successfully written by the most
1128 recent print() or put().
1129 prompt - pattern to match a prompt
1131 $matchop = $obj->prompt;
1132 $prev = $obj->prompt($matchop);
1134 This method sets the pattern used to find a prompt in the input
1136 stream. It must be a string representing a valid perl pattern
1137 match operator. The methods login() and cmd() try to read until
1138 matching the prompt. They will fail with a time-out error if the
1139 pattern you've chosen doesn't match what the remote side sends.
1140 With no argument this method returns the prompt set in the object.
1142 With an argument it sets the prompt to $matchop and returns the
1143 previous value.
1144 The default prompt is '/[\$%#>] $/'
1146 Always use single quotes, instead of double quotes, to construct
1148 $matchop (e.g. '/bash\$ $/'). If you're constructing a DOS like
1149 file path, you'll need to use four backslashes to represent one
1150 (e.g. '/c:\\\\users\\\\bill>$/i').
1151 Of course don't forget about regexp metacharacters like ".", "[",
1153 or "$". You'll only need a single backslash to quote them. The
1154 anchor metacharacters "^" and "$" refer to positions in the input
1155 buffer.
1156 The error mode action is performed when attempting to set this
1158 attribute with a match operator missing its opening delimiter.
1159 put - write to object
1161 $ok = $obj->put($string);
1162 $ok = $obj->put(String => $string,
1164 [Binmode => $mode,]
1165 [Errmode => $errmode,]
1166 [Telnetmode => $mode,]
1167 [Timeout => $secs,]);
1168 This method writes $string to the opened object and returns 1 if
1170 all data was successfully written. This method is like print()
1171 except that it doesn't write the trailing output_record_separator
1172 ("\n" by default). On time-out or other failures, the error mode
1173 action is performed. See errmode().
1174 On failure, it's possible that some data was written. If you
1176 choose to try and recover from a put timing-out, use print_length()
1177 to determine how much was written before the error occurred.
1178 Optional named parameters are provided to override the current
1180 settings of binmode, errmode, telnetmode, and timeout.
1181 rs - input line delimiter
1183 $chars = $obj->rs;
1184 $prev = $obj->rs($chars);
1186 This method is synonymous with input_record_separator().
1188 sockfamily - IP address family of connected local socket
1190 $sockfamily = $obj->sockfamily;
1191 This method returns which IP address family open() used to
1193 successfully connect. It is most useful when the requested address
1194 family() for open() was "any". Values returned may be "ipv4",
1195 "ipv6", or "" (when not connected).
1196 sockhost - IP address of this end of the socket connection
1198 $ipaddr = $obj->sockhost;
1199 This method returns a string which is the IPv4 or IPv6 address the
1201 local socket is bound to. It returns "" when not connected.
1202 sockport - TCP port of this end of the socket connection
1204 $port = $obj->sockport;
1205 This method returns the port number which the local socket is bound
1207 to. It returns "" when not connected.
1208 telnetmode - turn off/on telnet command interpretation
1210 $mode = $obj->telnetmode;
1211 $prev = $obj->telnetmode($mode);
1213 This method controls whether or not TELNET commands in the data
1215 stream are recognized and handled. The TELNET protocol uses
1216 certain character sequences sent in the data stream to control the
1217 session. If the port you're connecting to isn't using the TELNET
1218 protocol, then you should turn this mode off. The default is on.
1219 If no argument is given, the current mode is returned.
1221 If $mode is 0 then telnet mode is off. If $mode is 1 then telnet
1223 mode is on.
1224 timed_out - time-out indicator
1226 $boolean = $obj->timed_out;
1227 $prev = $obj->timed_out($boolean);
1229 This method indicates if a previous read, write, or open method
1231 timed-out. Remember that timing-out is itself an error. To be
1232 able to invoke timed_out() after a time-out error, you'd have to
1233 change the default error mode to something other than "die". See
1234 errmode().
1235 With no argument this method returns 1 if the previous method
1237 timed-out. With an argument it sets the indicator. Normally, only
1238 internal methods set this indicator.
1239 timeout - I/O time-out interval
1241 $secs = $obj->timeout;
1242 $prev = $obj->timeout($secs);
1244 This method sets the timeout interval used when performing I/O or
1246 connecting to a port. When a method doesn't complete within the
1247 timeout interval then it's an error and the error mode action is
1248 performed.
1249 A timeout may be expressed as a relative or absolute value. If
1251 $secs is greater than or equal to the time the program started, as
1252 determined by $^T, then it's an absolute time value for when time-
1253 out occurs. The perl function time() may be used to obtain an
1254 absolute time value. For a relative time-out value less than $^T,
1255 time-out happens $secs from when the method begins.
1256 If $secs is 0 then time-out occurs if the data cannot be
1258 immediately read or written. Use the undefined value to turn off
1259 timing-out completely.
1260 With no argument this method returns the timeout set in the object.
1262 With an argument it sets the timeout to $secs and returns the
1263 previous value. The default timeout value is 10 seconds.
1264 A warning is printed to STDERR when attempting to set this
1266 attribute to something that is not an "undef" or a non-negative
1267 integer.
1268 waitfor - wait for pattern in the input
1270 $ok = $obj->waitfor($matchop);
1271 $ok = $obj->waitfor([Match => $matchop,]
1272 [String => $string,]
1273 [Binmode => $mode,]
1274 [Errmode => $errmode,]
1275 [Telnetmode => $mode,]
1276 [Timeout => $secs,]);
1277 ($prematch, $match) = $obj->waitfor($matchop);
1279 ($prematch, $match) = $obj->waitfor([Match => $matchop,]
1280 [String => $string,]
1281 [Binmode => $mode,]
1282 [Errmode => $errmode,]
1283 [Telnetmode => $mode,]
1284 [Timeout => $secs,]);
1285 This method reads until a pattern match or string is found in the
1287 input stream. All the characters before and including the match
1288 are removed from the input stream.
1289 In a list context the characters before the match and the matched
1291 characters are returned in $prematch and $match. In a scalar
1292 context, the matched characters and all characters before it are
1293 discarded and 1 is returned on success. On time-out, eof, or other
1294 failures, for both list and scalar context, the error mode action
1295 is performed. See errmode().
1296 You can specify more than one pattern or string by simply providing
1298 multiple Match and/or String named parameters. A $matchop must be
1299 a string representing a valid Perl pattern match operator. The
1300 $string is just a substring to find in the input stream.
1301 Use dump_log() to debug when this method keeps timing-out and you
1303 don't think it should.
1304 An optional named parameter is provided to override the current
1306 setting of timeout.
1307 To avoid unexpected backslash interpretation, always use single
1309 quotes instead of double quotes to construct a match operator
1310 argument for prompt() and waitfor() (e.g. '/bash\$ $/'). If you're
1311 constructing a DOS like file path, you'll need to use four
1312 backslashes to represent one (e.g. '/c:\\\\users\\\\bill>$/i').
1313 Of course don't forget about regexp metacharacters like ".", "[",
1315 or "$". You'll only need a single backslash to quote them. The
1316 anchor metacharacters "^" and "$" refer to positions in the input
1317 buffer.
1318 Optional named parameters are provided to override the current
1320 settings of binmode, errmode, telnetmode, and timeout.
1321
1323 RFC 854
1324 TELNET Protocol Specification
1325 http://tools.ietf.org/html/rfc854
1327 RFC 1143
1329 Q Method of Implementing TELNET Option Negotiation
1330 http://tools.ietf.org/html/rfc1143
1332 TELNET Option Assignments
1334 http://www.iana.org/assignments/telnet-options
1335
1337 Setting prompt() to match a user's shell prompt can be tricky. This
1338 example logs in without knowing the shell prompt and then sets it to
1339 match prompt(). It requires /usr/bin/env and /bin/sh on the remote
1340 host.
1341 my $host = 'your_destination_host_here';
1343 my $user = 'your_username_here';
1344 my $passwd = 'your_password_here';
1345 my ($t, @output);
1346 ## Create a Net::Telnet object.
1348 use Net::Telnet ();
1349 $t = new Net::Telnet (Timeout => 10);
1350 ## Connect and login.
1352 $t->open($host);
1353 $t->waitfor('/login: ?$/i');
1355 $t->print($user);
1356 $t->waitfor('/password: ?$/i');
1358 $t->print($passwd);
1359 ## Switch to a known shell, using a known prompt.
1361 $t->prompt('/<xPROMPTx> $/');
1362 $t->errmode("return");
1363 $t->cmd("exec /usr/bin/env 'PS1=<xPROMPTx> ' /bin/sh -i")
1365 or die "login failed to remote host $host";
1366 $t->errmode("die");
1368 ## Now you can do cmd() to your heart's content.
1370 @output = $t->cmd("uname -a");
1371 print @output;
1372 exit;
1374 Usually you want the remote TERM environment variable to be set to
1376 something like "dumb" so you don't read escape sequences meant to be
1377 interpreted by a display terminal. It is best to set it via cmd(), or
1378 via waitfor() and print(). It is also possible to negotiate the
1379 terminal type via telnet. Here is how to do that.
1380 ## Module import.
1382 use Net::Telnet qw(TELNET_IAC TELNET_SB TELNET_SE TELOPT_TTYPE);
1383 ## Global variables.
1385 my $Term;
1386 ## Main program.
1388 {
1389 my $host = "your_destination_host_here";
1390 my $user = "your_username_here";
1391 my $passwd = "your_password_here";
1392 my $prompt = '/bash\$ $/'; # your regexp for shell prompt here
1393 my $t;
1394 $t = new Net::Telnet (Prompt => $prompt);
1396 ## Set up callbacks to negotiate terminal type.
1398 $t->option_callback(sub {});
1399 $t->suboption_callback(\&subopt_callback);
1400 $t->option_accept(Do => TELOPT_TTYPE);
1401 ## Login and print value of TERM.
1403 $Term = "dumb";
1404 $t->open($host);
1405 $t->login($user, $passwd);
1406 print $t->cmd('hostname');
1407 print "TERM=", $t->cmd('echo $TERM');
1408 $t->close;
1409 exit;
1411 } # end main program
1412 sub subopt_callback {
1414 my ($t, $option, $parameters) = @_;
1415 my $telcmd;
1416 if ($option == TELOPT_TTYPE) {
1418 $telcmd = pack("C4 A* C2", TELNET_IAC, TELNET_SB, TELOPT_TTYPE, 0,
1419 $Term, TELNET_IAC, TELNET_SE);
1420 $t->put(String => $telcmd,
1421 Telnetmode => 0);
1422 }
1423 1;
1425 } # end sub subopt_callback
1426 You can also use Net::Telnet to interact with local programs. This
1428 example changes a user's login password. It introduces the spawn()
1429 subroutine to start a program and associate a filehandle with its
1430 standard I/O. Because the passwd program always prompts for passwords
1431 on its controlling terminal, the IO::Pty module is used to create a new
1432 pseudo terminal for use by passwd. The Net::Telnet object reads and
1433 writes to that pseudo terminal. To use the code below, substitute
1434 "changeme" with the actual old and new passwords.
1435 ## Main program. {
1437 my ($pty, $passwd);
1438 my $oldpw = "changeme";
1439 my $newpw = "changeme";
1440 ## Start passwd program.
1442 $pty = spawn("passwd");
1443 ## Create a Net::Telnet object to perform I/O on passwd's tty.
1445 use Net::Telnet;
1446 $passwd = new Net::Telnet (-fhopen => $pty,
1447 -timeout => 2,
1448 -output_record_separator => "\r",
1449 -telnetmode => 0,
1450 -cmd_remove_mode => 1);
1451 $passwd->errmode("return");
1452 ## Send existing password.
1454 $passwd->waitfor('/password: ?$/i')
1455 or die "no old password prompt: ", $passwd->lastline;
1456 $passwd->print($oldpw);
1457 ## Send new password.
1459 $passwd->waitfor('/new (\w+\s)?password: ?$/i')
1460 or die "bad old password: ", $passwd->lastline;
1461 $passwd->print($newpw);
1462 ## Send new password verification.
1464 $passwd->waitfor('/new (\w+\s)?password: ?$/i')
1465 or die "bad new password: ", $passwd->lastline;
1466 $passwd->print($newpw);
1467 ## Display success or failure.
1469 $passwd->waitfor('/(changed|updated)/')
1470 or die "bad new password: ", $passwd->lastline;
1471 print $passwd->lastline;
1472 $passwd->close;
1474 exit;
1475 } # end main program
1476 sub spawn {
1478 my (@cmd) = @_;
1479 my ($pid, $pty, $tty, $tty_fd);
1480 ## Create a new pseudo terminal.
1482 use IO::Pty ();
1483 $pty = new IO::Pty
1484 or die $!;
1485 ## Execute the program in another process.
1487 unless ($pid = fork) { # child process
1488 die "problem spawning program: $!\n" unless defined $pid;
1489 ## Disassociate process from its controlling terminal.
1491 use POSIX ();
1492 POSIX::setsid()
1493 or die "setsid failed: $!";
1494 ## Associate process with a new controlling terminal.
1496 $pty->make_slave_controlling_terminal;
1497 $tty = $pty->slave;
1498 $tty_fd = $tty->fileno;
1499 close $pty;
1500 ## Make standard I/O use the new controlling terminal.
1502 open STDIN, "<&$tty_fd" or die $!;
1503 open STDOUT, ">&$tty_fd" or die $!;
1504 open STDERR, ">&STDOUT" or die $!;
1505 close $tty;
1506 ## Execute requested program.
1508 exec @cmd
1509 or die "problem executing $cmd[0]\n";
1510 } # end child process
1511 $pty;
1513 } # end sub spawn
1514 Here is an example that uses the openssh program to connect to a remote
1516 host. It uses the spawn() subroutine, from the password changing
1517 example above, to start the ssh program and then read and write to it
1518 via a Net::Telnet object. This example turns off ssh host key
1519 checking, which reduces your ability to know when someone on the
1520 network is impersonating the remote host. To use the code below,
1521 substitute "changeme" with the actual host, user, password, and command
1522 prompt.
1523 ## Main program.
1525 {
1526 my $host = "changeme";
1527 my $user = "changeme";
1528 my $passwd = "changeme";
1529 my $prompt = '/changeme\$ $/';
1530 my ($buf, $match, $pty, $ssh, @lines);
1531 ## Start ssh program.
1533 $pty = spawn("ssh",
1534 "-l", $user,
1535 "-e", "none",
1536 "-F", "/dev/null",
1537 "-o", "PreferredAuthentications=password",
1538 "-o", "NumberOfPasswordPrompts=1",
1539 "-o", "StrictHostKeyChecking=no",
1540 "-o", "UserKnownHostsFile=/dev/null",
1541 $host);
1542 ## Create a Net::Telnet object to perform I/O on ssh's tty.
1544 use Net::Telnet;
1545 $ssh = new Net::Telnet (-fhopen => $pty,
1546 -prompt => $prompt,
1547 -telnetmode => 0,
1548 -output_record_separator => "\r",
1549 -cmd_remove_mode => 1);
1550 ## Wait for the password prompt and send password.
1552 $ssh->waitfor(-match => '/password: ?$/i',
1553 -errmode => "return")
1554 or die "problem connecting to \"$host\": ", $ssh->lastline;
1555 $ssh->print($passwd);
1556 ## Wait for the shell prompt.
1558 (undef, $match) = $ssh->waitfor(-match => $ssh->prompt,
1559 -match => '/^Permission denied/m',
1560 -errmode => "return")
1561 or return $ssh->error("login failed: expected shell prompt ",
1562 "doesn't match actual\n");
1563 return $ssh->error("login failed: bad login-name or password\n")
1564 if $match =~ /^Permission denied/m;
1565 ## Run commands on remote host.
1567 print $ssh->cmd("hostname");
1568 print $ssh->cmd("uptime");
1569 $ssh->close;
1571 exit;
1572 } # end main program
1573 Some shells have a rather restrictive 255 character line limit. If you
1575 run into this problem, here is an example for sending lines longer than
1576 254 as a sequence of shorter lines.
1577 ## Main program.
1579 {
1580 my $host = "changeme";
1581 my $user = "changeme";
1582 my $passwd = "changeme";
1583 my $prompt = '/changeme\$ $/';
1584 my $cmd = join("", "echo ",
1585 "11111111112222222222333333333344444444445555555555",
1586 "66666666667777777777888888888899999999990000000000",
1587 "11111111112222222222333333333344444444445555555555",
1588 "66666666667777777777888888888899999999990000000000",
1589 "11111111112222222222333333333344444444445555555555",
1590 "66666666667777777777888888888899999999990000000000");
1591 use Net::Telnet ();
1593 my $t = new Net::Telnet (-prompt => $prompt);
1594 $t->open($host);
1595 $t->login($user, $passwd);
1596 my @output = cmd_unixlong($t, $cmd);
1598 print @output;
1599 exit;
1601 } # end main program
1602 sub cmd_unixlong {
1604 my ($obj, $cmd) = @_;
1605 my ($line, $pos);
1606 my $max_tty_line = 254;
1607 ## Start a Bourne shell.
1609 $obj->cmd(-string => "/usr/bin/env " .
1610 "'PS1=<xPROMPTx> ' 'PS2=<xPROMPTx> ' /bin/sh -i",
1611 -prompt => '/<xPROMPTx> $/')
1612 or return;
1613 ## Break-up the one large command line and send as shorter lines.
1615 $pos = 0;
1616 while (1) {
1617 $line = substr $cmd, $pos, $max_tty_line;
1618 $pos += length $line;
1619 last unless $pos < length $cmd;
1620 ## Send the line with continuation char.
1622 $obj->cmd(-string => "$line\\",
1623 -prompt => '/<xPROMPTx> $/')
1624 or return;
1625 }
1626 ## Send the last line and return the output.
1628 $obj->cmd("$line ; exit");
1629 } # end sub cmd_unixlong
1630
1632 Jay Rogers <jay@rgrs.com>
1633
1635 Dave Martin, Dave Cardosi
1636
1638 Copyright 1997, 2000, 2002, 2013, 2021 by Jay Rogers. All rights
1639 reserved. This program is free software; you can redistribute it
1640 and/or modify it under the same terms as Perl itself.
1641perl v5.38.0 2023-07-21 Net::Telnet(3)