1ZSHTCPSYS(1) General Commands Manual ZSHTCPSYS(1)
2
6 zshtcpsys - zsh tcp system
7
9 A module zsh/net/tcp is provided to provide network I/O over TCP/IP
10 from within the shell; see its description in zshmodules(1) . This
11 manual page describes a function suite based on the module. If the
12 module is installed, the functions are usually installed at the same
13 time, in which case they will be available for autoloading in the
14 default function search path. In addition to the zsh/net/tcp module,
15 the zsh/zselect module is used to implement timeouts on read opera‐
16 tions. For troubleshooting tips, consult the corresponding advice for
17 the zftp functions described in zshftpsys(1) .
18 There are functions corresponding to the basic I/O operations open,
20 close, read and send, named tcp_open etc., as well as a function
21 tcp_expect for pattern match analysis of data read as input. The sys‐
22 tem makes it easy to receive data from and send data to multiple named
23 sessions at once. In addition, it can be linked with the shell's line
24 editor in such a way that input data is automatically shown at the ter‐
25 minal. Other facilities available including logging, filtering and
26 configurable output prompts.
27 To use the system where it is available, it should be enough to
29 `autoload -U tcp_open' and run tcp_open as documented below to start a
30 session. The tcp_open function will autoload the remaining functions.
31
33 Basic I/O
34 tcp_open [-qz] host port [ sess ]
35 tcp_open [-qz] [ -s sess | -l sess,... ] ...
36 tcp_open [-qz] [-a fd | -f fd ] [ sess ]
37 Open a new session. In the first and simplest form, open a TCP
38 connection to host host at port port; numeric and symbolic forms
39 are understood for both.
40 If sess is given, this becomes the name of the session which can
42 be used to refer to multiple different TCP connections. If sess
43 is not given, the function will invent a numeric name value
44 (note this is not the same as the file descriptor to which the
45 session is attached). It is recommended that session names not
46 include `funny' characters, where funny characters are not
47 well-defined but certainly do not include alphanumerics or
48 underscores, and certainly do include whitespace.
49 In the second case, one or more sessions to be opened are given
51 by name. A single session name is given after -s and a
52 comma-separated list after -l; both options may be repeated as
53 many times as necessary. The host and port are read from the
54 file .ztcp_sessions in the same directory as the user's zsh ini‐
55 tialisation files, i.e. usually the home directory, but $ZDOTDIR
56 if that is set. The file consists of lines each giving a ses‐
57 sion name and the corresponding host and port, in that order
58 (note the session name comes first, not last), separated by
59 whitespace.
60 The third form allows passive and fake TCP connections. If the
62 option -a is used, its argument is a file descriptor open for
63 listening for connections. No function front-end is provided to
64 open such a file descriptor, but a call to `ztcp -l port' will
65 create one with the file descriptor stored in the parameter
66 $REPLY. The listening port can be closed with `ztcp -c fd'. A
67 call to `tcp_open -a fd' will block until a remote TCP connec‐
68 tion is made to port on the local machine. At this point, a
69 session is created in the usual way and is largely indistin‐
70 guishable from an active connection created with one of the
71 first two forms.
72 If the option -f is used, its argument is a file descriptor
74 which is used directly as if it were a TCP session. How well
75 the remainder of the TCP function system copes with this depends
76 on what actually underlies this file descriptor. A regular file
77 is likely to be unusable; a FIFO (pipe) of some sort will work
78 better, but note that it is not a good idea for two different
79 sessions to attempt to read from the same FIFO at once.
80 If the option -q is given with any of the three forms, tcp_open
82 will not print informational messages, although it will in any
83 case exit with an appropriate status.
84 If the line editor (zle) is in use, which is typically the case
86 if the shell is interactive, tcp_open installs a handler inside
87 zle which will check for new data at the same time as it checks
88 for keyboard input. This is convenient as the shell consumes no
89 CPU time while waiting; the test is performed by the operating
90 system. Giving the option -z to any of the forms of tcp_open
91 prevents the handler from being installed, so data must be read
92 explicitly. Note, however, this is not necessary for executing
93 complete sets of send and read commands from a function, as zle
94 is not active at this point. Generally speaking, the handler is
95 only active when the shell is waiting for input at a command
96 prompt or in the vared builtin. The option has no effect if zle
97 is not active; `[[ -o zle]]' will test for this.
98 The first session to be opened becomes the current session and
100 subsequent calls to tcp_open do not change it. The current ses‐
101 sion is stored in the parameter $TCP_SESS; see below for more
102 detail about the parameters used by the system.
103 tcp_close [-qn] [ -a | -l sess,... | sess ... ]
105 Close the named sessions, or the current session if none is
106 given, or all open sessions if -a is given. The options -l and
107 -s are both handled for consistency with tcp_open, although the
108 latter is redundant.
109 If the session being closed is the current one, $TCP_SESS is
111 unset, leaving no current session, even if there are other ses‐
112 sions still open.
113 If the session was opened with tcp_open -f, the file descriptor
115 is closed so long as it is in the range 0 to 9 accessible
116 directly from the command line. If the option -n is given, no
117 attempt will be made to close file descriptors in this case.
118 The -n option is not used for genuine ztcp session; the file
119 descriptors are always closed with the session.
120 If the option -q is given, no informational messages will be
122 printed.
123 tcp_read [-bdq] [ -t TO ] [ -T TO ]
125 [ -a | -u fd ... | -l sess,... | -s sess ...]
126 Perform a read operation on the current session, or on a list of
127 sessions if any are given with -u, -l or -s, or all open ses‐
128 sions if the option -a is given. Any of the -u, -l or -s
129 options may be repeated or mixed together. The -u option speci‐
130 fies a file descriptor directly (only those managed by this sys‐
131 tem are useful), the other two specify sessions as described for
132 tcp_open above.
133 The function checks for new data available on all the sessions
135 listed. Unless the -b option is given, it will not block wait‐
136 ing for new data. Any one line of data from any of the avail‐
137 able sessions will be read, stored in the parameter $TCP_LINE,
138 and displayed to standard output unless $TCP_SILENT contains a
139 non-empty string. When printed to standard output the string
140 $TCP_PROMPT will be shown at the start of the line; the default
141 form for this includes the name of the session being read. See
142 below for more information on these parameters. In this mode,
143 tcp_read can be called repeatedly until it returns status 2
144 which indicates all pending input from all specified sessions
145 has been handled.
146 With the option -b, equivalent to an infinite timeout, the func‐
148 tion will block until a line is available to read from one of
149 the specified sessions. However, only a single line is
150 returned.
151 The option -d indicates that all pending input should be
153 drained. In this case tcp_read may process multiple lines in
154 the manner given above; only the last is stored in $TCP_LINE,
155 but the complete set is stored in the array $tcp_lines. This is
156 cleared at the start of each call to tcp_read.
157 The options -t and -T specify a timeout in seconds, which may be
159 a floating point number for increased accuracy. With -t the
160 timeout is applied before each line read. With -T, the timeout
161 applies to the overall operation, possibly including multiple
162 read operations if the option -d is present; without this
163 option, there is no distinction between -t and -T.
164 The function does not print informational messages, but if the
166 option -q is given, no error message is printed for a non-exis‐
167 tent session.
168 A return value of 2 indicates a timeout or no data to read. Any
170 other non-zero return value indicates some error condition.
171 See tcp_log for how to control where data is sent by tcp_read.
173 tcp_send [-nq] [ -s sess | -l sess,... ] data ...
175 tcp_send [-nq] -a data ...
176 Send the supplied data strings to all the specified sessions in
177 turn. The underlying operation differs little from a `print -r'
178 to the session's file descriptor, although it attempts to pre‐
179 vent the shell from dying owing to a SIGPIPE caused by an
180 attempt to write to a defunct session.
181 The option -n prevents tcp_send from putting a newline at the
183 end of the data strings.
184 The remaining options all behave as for tcp_read.
186 The data arguments are not further processed once they have been
188 passed to tcp_send; they are simply passed down to print -r.
189 If the parameter $TCP_OUTPUT is a non-empty string and logging
191 is enabled then the data sent to each session will be echoed to
192 the log file(s) with $TCP_OUTPUT in front where appropriate,
193 much in the manner of $TCP_PROMPT.
194 Session Management
196 tcp_alias [-q] alias=sess ...
197 tcp_alias [-q] [ alias ] ...
198 tcp_alias -d [-q] alias ...
199 This function is not particularly well tested.
200 The first form creates an alias for a session name; alias can
202 then be used to refer to the existing session sess. As many
203 aliases may be listed as required.
204 The second form lists any aliases specified, or all aliases if
206 none.
207 The third form deletes all the aliases listed. The underlying
209 sessions are not affected.
210 The option -q suppresses an inconsistently chosen subset of
212 error messages.
213 tcp_log [-asc] [ -n | -N ] [ logfile ]
215 With an argument logfile, all future input from tcp_read will be
216 logged to the named file. Unless -a (append) is given, this
217 file will first be truncated or created empty. With no argu‐
218 ments, show the current status of logging.
219 With the option -s, per-session logging is enabled. Input from
221 tcp_read is output to the file logfile.sess. As the session is
222 automatically discriminated by the filename, the contents are
223 raw (no $TCP_PROMPT). The option -a applies as above.
224 Per-session logging and logging of all data in one file are not
225 mutually exclusive.
226 The option -c closes all logging, both complete and per-session
228 logs.
229 The options -n and -N respectively turn off or restore output of
231 data read by tcp_read to standard output; hence `tcp_log -cn'
232 turns off all output by tcp_read.
233 The function is purely a convenient front end to setting the
235 parameters $TCP_LOG, $TCP_LOG_SESS, $TCP_SILENT, which are
236 described below.
237 tcp_rename old new
239 Rename session old to session new. The old name becomes
240 invalid.
241 tcp_sess [ sess [ command ... ] ]
243 With no arguments, list all the open sessions and associated
244 file descriptors. The current session is marked with a star.
245 For use in functions, direct access to the parameters
246 $tcp_by_name, $tcp_by_fd and $TCP_SESS is probably more conve‐
247 nient; see below.
248 With a sess argument, set the current session to sess. This is
250 equivalent to changing $TCP_SESS directly.
251 With additional arguments, temporarily set the current session
253 while executing the string command .... The first argument is
254 re-evaluated so as to expand aliases etc., but the remaining
255 arguments are passed through as the appear to tcp_sess. The
256 original session is restored when tcp_sess exits.
257 Advanced I/O
259 tcp_command send-options ... send-arguments ...
260 This is a convenient front-end to tcp_send. All arguments are
261 passed to tcp_send, then the function pauses waiting for data.
262 While data is arriving at least every $TCP_TIMEOUT (default 0.3)
263 seconds, data is handled and printed out according to the cur‐
264 rent settings. Status 0 is always returned.
265 This is generally only useful for interactive use, to prevent
267 the display becoming fragmented by output returned from the con‐
268 nection. Within a programme or function it is generally better
269 to handle reading data by a more explicit method.
270 tcp_expect [ -q ] [ -p var ] [ -t to | -T TO]
272 [ -a | -s sess ... | -l sess,... ] pattern ...
273 Wait for input matching any of the given patterns from any of
274 the specified sessions. Input is ignored until an input line
275 matches one of the given patterns; at this point status zero is
276 returned, the matching line is stored in $TCP_LINE, and the full
277 set of lines read during the call to tcp_expect is stored in the
278 array $tcp_expect_lines.
279 Sessions are specified in the same way as tcp_read: the default
281 is to use the current session, otherwise the sessions specified
282 by -a, -s, or -l are used.
283 Each pattern is a standard zsh extended-globbing pattern; note
285 that it needs to be quoted to avoid it being expanded immedi‐
286 ately by filename generation. It must match the full line, so
287 to match a substring there must be a `*' at the start and end.
288 The line matched against includes the $TCP_PROMPT added by
289 tcp_read. It is possible to include the globbing flags `#b' or
290 `#m' in the patterns to make backreferences available in the
291 parameters $MATCH, $match, etc., as described in the base zsh
292 documentation on pattern matching.
293 Unlike tcp_read, the default behaviour of tcp_expect is to block
295 indefinitely until the required input is found. This can be
296 modified by specifying a timeout with -t or -T; these function
297 as in tcp_read, specifying a per-read or overall timeout,
298 respectively, in seconds, as an integer or floating-point num‐
299 ber. As tcp_read, the function returns status 2 if a timeout
300 occurs.
301 The function returns as soon as any one of the patterns given
303 match. If the caller needs to know which of the patterns
304 matched, the option -p var can be used; on return, $var is set
305 to the number of the pattern using ordinary zsh indexing, i.e.
306 the first is 1, and so on. Note the absence of a `$' in front
307 of var. To avoid clashes, the parameter cannot begin with
308 `_expect'.
309 The option -q is passed directly down to tcp_read.
311 As all input is done via tcp_read, all the usual rules about
313 output of lines read apply. One exception is that the parameter
314 $tcp_lines will only reflect the line actually matched by
315 tcp_expect; use $tcp_expect_lines for the full set of lines read
316 during the function call.
317 tcp_proxy
319 This is a simple-minded function to accept a TCP connection and
320 execute a command with I/O redirected to the connection.
321 Extreme caution should be taken as there is no security whatso‐
322 ever and this can leave your computer open to the world. Ide‐
323 ally, it should only be used behind a firewall.
324 The first argument is a TCP port on which the function will lis‐
326 ten.
327 The remaining arguments give a command and its arguments to exe‐
329 cute with standard input, standard output and standard error
330 redirected to the file descriptor on which the TCP session has
331 been accepted. If no command is given, a new zsh is started.
332 This gives everyone on your network direct access to your
333 account, which in many cases will be a bad thing.
334 The command is run in the background, so tcp_proxy can then
336 accept new connections. It continues to accept new connections
337 until interrupted.
338 tcp_spam [-ertv] [ -a | -s sess | -l sess,... ] cmd ...
340 Execute `cmd ...' for each session in turn. Note this executes
341 the command and arguments; it does not send the command line as
342 data unless the -t (transmit) option is given.
343 The sessions may be selected explicitly with the standard -a, -s
345 or -l options, or may be chosen implicitly. If none of the
346 three options is given the rules are: first, if the array
347 $tcp_spam_list is set, this is taken as the list of sessions,
348 otherwise all sessions are taken. Second, any sessions given in
349 the array $tcp_no_spam_list are removed from the list of ses‐
350 sions.
351 Normally, any sessions added by the `-a' flag or when all ses‐
353 sions are chosen implicitly are spammed in alphabetic order;
354 sessions given by the $tcp_spam_list array or on the command
355 line are spammed in the order given. The -r flag reverses the
356 order however it was arrived it.
357 The -v flag specifies that a $TCP_PROMPT will be output before
359 each session. This is output after any modification to TCP_SESS
360 by the user-defined tcp_on_spam function described below.
361 (Obviously that function is able to generate its own output.)
362 If the option -e is present, the line given as cmd ... is exe‐
364 cuted using eval, otherwise it is executed without any further
365 processing.
366 tcp_talk
368 This is a fairly simple-minded attempt to force input to the
369 line editor to go straight to the default TCP_SESSION.
370 An escape string, $TCP_TALK_ESCAPE, default `:', is used to
372 allow access to normal shell operation. If it is on its own at
373 the start of the line, or followed only by whitespace, the line
374 editor returns to normal operation. Otherwise, the string and
375 any following whitespace are skipped and the remainder of the
376 line executed as shell input without any change of the line edi‐
377 tor's operating mode.
378 The current implementation is somewhat deficient in terms of use
380 of the command history. For this reason, many users will prefer
381 to use some form of alternative approach for sending data easily
382 to the current session. One simple approach is to alias some
383 special character (such as `%') to `tcp_command --'.
384 tcp_wait
386 The sole argument is an integer or floating point number which
387 gives the seconds to delay. The shell will do nothing for that
388 period except wait for input on all TCP sessions by calling
389 tcp_read -a. This is similar to the interactive behaviour at
390 the command prompt when zle handlers are installed.
391 `One-shot' file transfer
393 tcp_point port
394 tcp_shoot host port
395 This pair of functions provide a simple way to transfer a file
396 between two hosts within the shell. Note, however, that bulk
397 data transfer is currently done using cat. tcp_point reads any
398 data arriving at port and sends it to standard output; tcp_shoot
399 connects to port on host and sends its standard input. Any
400 unused port may be used; the standard mechanism for picking a
401 port is to think of a random four-digit number above 1024 until
402 one works.
403 To transfer a file from host woodcock to host springes, on
405 springes:
406 tcp_point 8091 >output_file
408 and on woodcock:
410 tcp_shoot springes 8091 <input_file
412 As these two functions do not require tcp_open to set up a TCP
414 connection first, they may need to be autoloaded separately.
415
417 Certain functions, if defined by the user, will be called by the func‐
418 tion system in certain contexts. This facility depends on the module
419 zsh/parameter, which is usually available in interactive shells as the
420 completion system depends on it. None of the functions need be
421 defined; they simply provide convenient hooks when necessary.
422 Typically, these are called after the requested action has been taken,
424 so that the various parameters will reflect the new state.
425 tcp_on_alias alias fd
427 When an alias is defined, this function will be called with two
428 arguments: the name of the alias, and the file descriptor of the
429 corresponding session.
430 tcp_on_close sess fd
432 This is called with the name of a session being closed and the
433 file descriptor which corresponded to that session. Both will
434 be invalid by the time the function is called.
435 tcp_on_open sess fd
437 This is called after a new session has been defined with the
438 session name and file descriptor as arguments.
439 tcp_on_rename oldsess fd newsess
441 This is called after a session has been renamed with the three
442 arguments old session name, file descriptor, new session name.
443 tcp_on_spam sess command ...
445 This is called once for each session spammed, just before a com‐
446 mand is executed for a session by tcp_spam. The arguments are
447 the session name followed by the command list to be executed.
448 If tcp_spam was called with the option -t, the first command
449 will be tcp_send.
450 This function is called after $TCP_SESS is set to reflect the
452 session to be spammed, but before any use of it is made. Hence
453 it is possible to alter the value of $TCP_SESS within this func‐
454 tion. For example, the session arguments to tcp_spam could
455 include extra information to be stripped off and processed in
456 tcp_on_spam.
457 If the function sets the parameter $REPLY to `done', the command
459 line is not executed; in addition, no prompt is printed for the
460 -v option to tcp_spam.
461 tcp_on_unalias alias fd
463 This is called with the name of an alias and the corresponding
464 session's file descriptor after an alias has been deleted.
465
467 The following functions are used by the TCP function system but will
468 rarely if ever need to be called directly.
469 tcp_fd_handler
471 This is the function installed by tcp_open for handling input
472 from within the line editor, if that is required. It is in the
473 format documented for the builtin `zle -F' in zshzle(1) .
474 While active, the function sets the parameter TCP_HANDLER_ACTIVE
476 to 1. This allows shell code called internally (for example, by
477 setting tcp_on_read) to tell if is being called when the shell
478 is otherwise idle at the editor prompt.
479 tcp_output [ -q ] -P prompt -F fd -S sess
481 This function is used for both logging and handling output to
482 standard output, from within tcp_read and (if $TCP_OUTPUT is
483 set) tcp_send.
484 The prompt to use is specified by -P; the default is the empty
486 string. It can contain:
487 %c Expands to 1 if the session is the current session, oth‐
488 erwise 0. Used with ternary expresions such as
489 `%(c.-.+)' to output `+' for the current session and `-'
490 otherwise.
491 %f Replaced by the session's file descriptor.
493 %s Replaced by the session name.
495 %% Replaced by a single `%'.
497 The option -q suppresses output to standard output, but not to
499 any log files which are configured.
500 The -S and -F options are used to pass in the session name and
502 file descriptor for possible replacement in the prompt.
503
505 Parameters follow the usual convention that uppercase is used for
506 scalars and integers, while lowercase is used for normal and associa‐
507 tive array. It is always safe for user code to read these parameters.
508 Some parameters may also be set; these are noted explicitly. Others
509 are included in this group as they are set by the function system for
510 the user's benefit, i.e. setting them is typically not useful but is
511 benign.
512 It is often also useful to make settable parameters local to a func‐
514 tion. For example, `local TCP_SILENT=1' specifies that data read dur‐
515 ing the function call will not be printed to standard output, regard‐
516 less of the setting outside the function. Likewise, `local
517 TCP_SESS=sess' sets a session for the duration of a function, and
518 `local TCP_PROMPT=' specifies that no prompt is used for input during
519 the function.
520 tcp_expect_lines
522 Array. The set of lines read during the last call to
523 tcp_expect, including the last ($TCP_LINE).
524 tcp_filter
526 Array. May be set directly. A set of extended globbing patterns
527 which, if matched in tcp_output, will cause the line not to be
528 printed to standard output. The patterns should be defined as
529 described for the arguments to tcp_expect. Output of line to
530 log files is not affected.
531 TCP_HANDLER_ACTIVE
533 Scalar. Set to 1 within tcp_fd_handler to indicate to functions
534 called recursively that they have been called during an editor
535 session. Otherwise unset.
536 TCP_LINE
538 The last line read by tcp_read, and hence also tcp_expect.
539 TCP_LINE_FD
541 The file descriptor from which $TCP_LINE was read.
542 ${tcp_by_fd[$TCP_LINE_FD]} will give the corresponding session
543 name.
544 tcp_lines
546 Array. The set of lines read during the last call to tcp_read,
547 including the last ($TCP_LINE).
548 TCP_LOG
550 May be set directly, although it is also controlled by tcp_log.
551 The name of a file to which output from all sessions will be
552 sent. The output is proceeded by the usual $TCP_PROMPT. If it
553 is not an absolute path name, it will follow the user's current
554 directory.
555 TCP_LOG_SESS
557 May be set directly, although it is also controlled by tcp_log.
558 The prefix for a set of files to which output from each session
559 separately will be sent; the full filename is
560 ${TCP_LOG_SESS}.sess. Output to each file is raw; no prompt is
561 added. If it is not an absolute path name, it will follow the
562 user's current directory.
563 tcp_no_spam_list
565 Array. May be set directly. See tcp_spam for how this is used.
566 TCP_OUTPUT
568 May be set directly. If a non-empty string, any data sent to a
569 session by tcp_send will be logged. This parameter gives the
570 prompt to be used in a file specified by $TCP_LOG but not in a
571 file generated from $TCP_LOG_SESS. The prompt string has the
572 same format as TCP_PROMPT and the same rules for its use apply.
573 TCP_PROMPT
575 May be set directly. Used as the prefix for data read by
576 tcp_read which is printed to standard output or to the log file
577 given by $TCP_LOG, if any. Any `%s', `%f' or `%%' occurring in
578 the string will be replaced by the name of the session, the ses‐
579 sion's underlying file descriptor, or a single `%', respec‐
580 tively. The expression `%c' expands to 1 if the session being
581 read is the current session, else 0; this is most useful in
582 ternary expressions such as `%(c.-.+)' which outputs `+' if the
583 session is the current one, else `-'.
584 TCP_READ_DEBUG
586 May be set directly. If this has non-zero length, tcp_read will
587 give some limited diagnostics about data being read.
588 TCP_SECONDS_START
590 This value is created and initialised to zero by tcp_open.
591 The functions tcp_read and tcp_expect use the shell's SECONDS
593 parameter for their own timing purposes. If that parameter is
594 not of floating point type on entry to one of the functions, it
595 will create a local parameter SECONDS which is floating point
596 and set the parameter TCP_SECONDS_START to the previous value of
597 $SECONDS. If the parameter is already floating point, it is
598 used without a local copy being created and TCP_SECONDS_START is
599 not set. As the global value is zero, the shell elapsed time is
600 guaranteed to be the sum of $SECONDS and $TCP_SECONDS_START.
601 This can be avoided by setting SECONDS globally to a floating
603 point value using `typeset -F SECONDS'; then the TCP functions
604 will never make a local copy and never set TCP_SECONDS_START to
605 a non-zero value.
606 TCP_SESS
608 May be set directly. The current session; must refer to one of
609 the sessions established by tcp_open.
610 TCP_SILENT
612 May be set directly, although it is also controlled by tcp_log.
613 If of non-zero length, data read by tcp_read will not be written
614 to standard output, though may still be written to a log file.
615 tcp_spam_list
617 Array. May be set directly. See the description of the func‐
618 tion tcp_spam for how this is used.
619 TCP_TALK_ESCAPE
621 May be set directly. See the description of the function
622 tcp_talk for how this is used.
623 TCP_TIMEOUT
625 May be set directly. Currently this is only used by the func‐
626 tion tcp_command, see above.
627
629 The following parameters are not set by the function system, but have a
630 special effect if set by the user.
631 tcp_on_read
633 This should be an associative array; if it is not, the behaviour
634 is undefined. Each key is the name of a shell function or other
635 command, and the corresponding value is a shell pattern (using
636 EXTENDED_GLOB). Every line read from a TCP session directly or
637 indirectly using tcp_read (which includes lines read by
638 tcp_expect) is compared against the pattern. If the line
639 matches, the command given in the key is called with two argu‐
640 ments: the name of the session from which the line was read, and
641 the line itself.
642 If any function called to handle a line returns a non-zero sta‐
644 tus, the line is not output. Thus a tcp_on_read handler con‐
645 taining only the instruction `return 1' can be used to suppress
646 output of particular lines (see, however, tcp_filter above).
647 However, the line is still stored in TCP_LINE and tcp_lines;
648 this occurs after all tcp_on_read processing.
649
651 These parameters are controlled by the function system; they may be
652 read directly, but should not usually be set by user code.
653 tcp_aliases
655 Associative array. The keys are the names of sessions estab‐
656 lished with tcp_open; each value is a space-separated list of
657 aliases which refer to that session.
658 tcp_by_fd
660 Associative array. The keys are session file descriptors; each
661 value is the name of that session.
662 tcp_by_name
664 Associative array. The keys are the names of sessions; each
665 value is the file descriptor associated with that session.
666
668 Here is a trivial example using a remote calculator.
669 TO create a calculator server on port 7337 (see the dc manual page for
671 quite how infuriating the underlying command is):
672 tcp_proxy 7337 dc
674 To connect to this from the same host with a session also named `dc':
676 tcp_open localhost 7337 dc
678 To send a command to the remote session and wait a short while for out‐
680 put (assuming dc is the current session):
681 tcp_command 2 4 + p
683 To close the session:
685 tcp_close
687 The tcp_proxy needs to be killed to be stopped. Note this will not
689 usually kill any connections which have already been accepted, and also
690 that the port is not immediately available for reuse.
691 The following chunk of code puts a list of sessions into an xterm
693 header, with the current session followed by a star.
694 print -n "\033]2;TCP:" ${(k)tcp_by_name:/$TCP_SESS/$TCP_SESS\*} "\a"
696
698 The function tcp_read uses the shell's normal read builtin. As this
699 reads a complete line at once, data arriving without a terminating new‐
700 line can cause the function to block indefinitely.
701 Though the function suite works well for interactive use and for data
703 arriving in small amounts, the performance when large amounts of data
704 are being exchanged is likely to be extremely poor.
705zsh 4.2.6 November 28, 2005 ZSHTCPSYS(1)