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 man‐
11 ual page describes a function suite based on the module. If the module
12 is installed, the functions are usually installed at the same time, in
13 which case they will be available for autoloading in the default func‐
14 tion search path. In addition to the zsh/net/tcp module, the zsh/zse‐
15 lect module is used to implement timeouts on read operations. For
16 troubleshooting tips, consult the corresponding advice for the zftp
17 functions described in zshzftpsys(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 `au‐
29 toload -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 un‐
48 derscores, 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. A failure to open any session causes
54 tcp_open to abort. The host and port are read from the file
55 .ztcp_sessions in the same directory as the user's zsh initiali‐
56 sation files, i.e. usually the home directory, but $ZDOTDIR if
57 that is set. The file consists of lines each giving a session
58 name and the corresponding host and port, in that order (note
59 the session name comes first, not last), separated by white‐
60 space.
61 The third form allows passive and fake TCP connections. If the
63 option -a is used, its argument is a file descriptor open for
64 listening for connections. No function front-end is provided to
65 open such a file descriptor, but a call to `ztcp -l port' will
66 create one with the file descriptor stored in the parameter $RE‐
67 PLY. The listening port can be closed with `ztcp -c fd'. A
68 call to `tcp_open -a fd' will block until a remote TCP connec‐
69 tion is made to port on the local machine. At this point, a
70 session is created in the usual way and is largely indistin‐
71 guishable from an active connection created with one of the
72 first two forms.
73 If the option -f is used, its argument is a file descriptor
75 which is used directly as if it were a TCP session. How well
76 the remainder of the TCP function system copes with this depends
77 on what actually underlies this file descriptor. A regular file
78 is likely to be unusable; a FIFO (pipe) of some sort will work
79 better, but note that it is not a good idea for two different
80 sessions to attempt to read from the same FIFO at once.
81 If the option -q is given with any of the three forms, tcp_open
83 will not print informational messages, although it will in any
84 case exit with an appropriate status.
85 If the line editor (zle) is in use, which is typically the case
87 if the shell is interactive, tcp_open installs a handler inside
88 zle which will check for new data at the same time as it checks
89 for keyboard input. This is convenient as the shell consumes no
90 CPU time while waiting; the test is performed by the operating
91 system. Giving the option -z to any of the forms of tcp_open
92 prevents the handler from being installed, so data must be read
93 explicitly. Note, however, this is not necessary for executing
94 complete sets of send and read commands from a function, as zle
95 is not active at this point. Generally speaking, the handler is
96 only active when the shell is waiting for input at a command
97 prompt or in the vared builtin. The option has no effect if zle
98 is not active; `[[ -o zle]]' will test for this.
99 The first session to be opened becomes the current session and
101 subsequent calls to tcp_open do not change it. The current ses‐
102 sion is stored in the parameter $TCP_SESS; see below for more
103 detail about the parameters used by the system.
104 The function tcp_on_open, if defined, is called when a session
106 is opened. See the description below.
107 tcp_close [ -qn ] [ -a | -l sess[,...] | sess ... ]
109 Close the named sessions, or the current session if none is
110 given, or all open sessions if -a is given. The options -l and
111 -s are both handled for consistency with tcp_open, although the
112 latter is redundant.
113 If the session being closed is the current one, $TCP_SESS is un‐
115 set, leaving no current session, even if there are other ses‐
116 sions still open.
117 If the session was opened with tcp_open -f, the file descriptor
119 is closed so long as it is in the range 0 to 9 accessible di‐
120 rectly from the command line. If the option -n is given, no at‐
121 tempt will be made to close file descriptors in this case. The
122 -n option is not used for genuine ztcp session; the file de‐
123 scriptors are always closed with the session.
124 If the option -q is given, no informational messages will be
126 printed.
127 tcp_read [ -bdq ] [ -t TO ] [ -T TO ]
130 [ -a | -u fd[,...] | -l sess[,...] | -s sess ... ]
131 Perform a read operation on the current session, or on a list of
132 sessions if any are given with -u, -l or -s, or all open ses‐
133 sions if the option -a is given. Any of the -u, -l or -s op‐
134 tions may be repeated or mixed together. The -u option speci‐
135 fies a file descriptor directly (only those managed by this sys‐
136 tem are useful), the other two specify sessions as described for
137 tcp_open above.
138 The function checks for new data available on all the sessions
140 listed. Unless the -b option is given, it will not block wait‐
141 ing for new data. Any one line of data from any of the avail‐
142 able sessions will be read, stored in the parameter $TCP_LINE,
143 and displayed to standard output unless $TCP_SILENT contains a
144 non-empty string. When printed to standard output the string
145 $TCP_PROMPT will be shown at the start of the line; the default
146 form for this includes the name of the session being read. See
147 below for more information on these parameters. In this mode,
148 tcp_read can be called repeatedly until it returns status 2
149 which indicates all pending input from all specified sessions
150 has been handled.
151 With the option -b, equivalent to an infinite timeout, the func‐
153 tion will block until a line is available to read from one of
154 the specified sessions. However, only a single line is re‐
155 turned.
156 The option -d indicates that all pending input should be
158 drained. In this case tcp_read may process multiple lines in
159 the manner given above; only the last is stored in $TCP_LINE,
160 but the complete set is stored in the array $tcp_lines. This is
161 cleared at the start of each call to tcp_read.
162 The options -t and -T specify a timeout in seconds, which may be
164 a floating point number for increased accuracy. With -t the
165 timeout is applied before each line read. With -T, the timeout
166 applies to the overall operation, possibly including multiple
167 read operations if the option -d is present; without this op‐
168 tion, there is no distinction between -t and -T.
169 The function does not print informational messages, but if the
171 option -q is given, no error message is printed for a non-exis‐
172 tent session.
173 A return status of 2 indicates a timeout or no data to read.
175 Any other non-zero return status indicates some error condition.
176 See tcp_log for how to control where data is sent by tcp_read.
178 tcp_send [ -cnq ] [ -s sess | -l sess[,...] ] data ...
180 tcp_send [ -cnq ] -a data ...
181 Send the supplied data strings to all the specified sessions in
182 turn. The underlying operation differs little from a `print -r'
183 to the session's file descriptor, although it attempts to pre‐
184 vent the shell from dying owing to a SIGPIPE caused by an at‐
185 tempt to write to a defunct session.
186 The option -c causes tcp_send to behave like cat. It reads
188 lines from standard input until end of input and sends them in
189 turn to the specified session(s) exactly as if they were given
190 as data arguments to individual tcp_send commands.
191 The option -n prevents tcp_send from putting a newline at the
193 end of the data strings.
194 The remaining options all behave as for tcp_read.
196 The data arguments are not further processed once they have been
198 passed to tcp_send; they are simply passed down to print -r.
199 If the parameter $TCP_OUTPUT is a non-empty string and logging
201 is enabled then the data sent to each session will be echoed to
202 the log file(s) with $TCP_OUTPUT in front where appropriate,
203 much in the manner of $TCP_PROMPT.
204 Session Management
206 tcp_alias [ -q ] alias=sess ...
207 tcp_alias [ -q ] [ alias ... ]
208 tcp_alias -d [ -q ] alias ...
209 This function is not particularly well tested.
210 The first form creates an alias for a session name; alias can
212 then be used to refer to the existing session sess. As many
213 aliases may be listed as required.
214 The second form lists any aliases specified, or all aliases if
216 none.
217 The third form deletes all the aliases listed. The underlying
219 sessions are not affected.
220 The option -q suppresses an inconsistently chosen subset of er‐
222 ror messages.
223 tcp_log [ -asc ] [ -n | -N ] [ logfile ]
225 With an argument logfile, all future input from tcp_read will be
226 logged to the named file. Unless -a (append) is given, this
227 file will first be truncated or created empty. With no argu‐
228 ments, show the current status of logging.
229 With the option -s, per-session logging is enabled. Input from
231 tcp_read is output to the file logfile.sess. As the session is
232 automatically discriminated by the filename, the contents are
233 raw (no $TCP_PROMPT). The option -a applies as above.
234 Per-session logging and logging of all data in one file are not
235 mutually exclusive.
236 The option -c closes all logging, both complete and per-session
238 logs.
239 The options -n and -N respectively turn off or restore output of
241 data read by tcp_read to standard output; hence `tcp_log -cn'
242 turns off all output by tcp_read.
243 The function is purely a convenient front end to setting the pa‐
245 rameters $TCP_LOG, $TCP_LOG_SESS, $TCP_SILENT, which are de‐
246 scribed below.
247 tcp_rename old new
249 Rename session old to session new. The old name becomes in‐
250 valid.
251 tcp_sess [ sess [ command [ arg ... ] ] ]
253 With no arguments, list all the open sessions and associated
254 file descriptors. The current session is marked with a star.
255 For use in functions, direct access to the parameters
256 $tcp_by_name, $tcp_by_fd and $TCP_SESS is probably more conve‐
257 nient; see below.
258 With a sess argument, set the current session to sess. This is
260 equivalent to changing $TCP_SESS directly.
261 With additional arguments, temporarily set the current session
263 while executing `command arg ...'. command is re-evaluated so
264 as to expand aliases etc., but the remaining args are passed
265 through as that appear to tcp_sess. The original session is re‐
266 stored when tcp_sess exits.
267 Advanced I/O
269 tcp_command send-option ... send-argument ...
270 This is a convenient front-end to tcp_send. All arguments are
271 passed to tcp_send, then the function pauses waiting for data.
272 While data is arriving at least every $TCP_TIMEOUT (default 0.3)
273 seconds, data is handled and printed out according to the cur‐
274 rent settings. Status 0 is always returned.
275 This is generally only useful for interactive use, to prevent
277 the display becoming fragmented by output returned from the con‐
278 nection. Within a programme or function it is generally better
279 to handle reading data by a more explicit method.
280 tcp_expect [ -q ] [ -p var | -P var ] [ -t TO | -T TO ]
283 [ -a | -s sess | -l sess[,...] ] pattern ...
284 Wait for input matching any of the given patterns from any of
285 the specified sessions. Input is ignored until an input line
286 matches one of the given patterns; at this point status zero is
287 returned, the matching line is stored in $TCP_LINE, and the full
288 set of lines read during the call to tcp_expect is stored in the
289 array $tcp_expect_lines.
290 Sessions are specified in the same way as tcp_read: the default
292 is to use the current session, otherwise the sessions specified
293 by -a, -s, or -l are used.
294 Each pattern is a standard zsh extended-globbing pattern; note
296 that it needs to be quoted to avoid it being expanded immedi‐
297 ately by filename generation. It must match the full line, so
298 to match a substring there must be a `*' at the start and end.
299 The line matched against includes the $TCP_PROMPT added by
300 tcp_read. It is possible to include the globbing flags `#b' or
301 `#m' in the patterns to make backreferences available in the pa‐
302 rameters $MATCH, $match, etc., as described in the base zsh doc‐
303 umentation on pattern matching.
304 Unlike tcp_read, the default behaviour of tcp_expect is to block
306 indefinitely until the required input is found. This can be
307 modified by specifying a timeout with -t or -T; these function
308 as in tcp_read, specifying a per-read or overall timeout, re‐
309 spectively, in seconds, as an integer or floating-point number.
310 As tcp_read, the function returns status 2 if a timeout occurs.
311 The function returns as soon as any one of the patterns given
313 match. If the caller needs to know which of the patterns
314 matched, the option -p var can be used; on return, $var is set
315 to the number of the pattern using ordinary zsh indexing, i.e.
316 the first is 1, and so on. Note the absence of a `$' in front
317 of var. To avoid clashes, the parameter cannot begin with `_ex‐
318 pect'. The index -1 is used if there is a timeout and 0 if
319 there is no match.
320 The option -P var works similarly to -p, but instead of numeri‐
322 cal indexes the regular arguments must begin with a prefix fol‐
323 lowed by a colon: that prefix is then used as a tag to which var
324 is set when the argument matches. The tag timeout is used if
325 there is a timeout and the empty string if there is no match.
326 Note it is acceptable for different arguments to start with the
327 same prefix if the matches do not need to be distinguished.
328 The option -q is passed directly down to tcp_read.
330 As all input is done via tcp_read, all the usual rules about
332 output of lines read apply. One exception is that the parameter
333 $tcp_lines will only reflect the line actually matched by
334 tcp_expect; use $tcp_expect_lines for the full set of lines read
335 during the function call.
336 tcp_proxy
338 This is a simple-minded function to accept a TCP connection and
339 execute a command with I/O redirected to the connection. Ex‐
340 treme caution should be taken as there is no security whatsoever
341 and this can leave your computer open to the world. Ideally, it
342 should only be used behind a firewall.
343 The first argument is a TCP port on which the function will lis‐
345 ten.
346 The remaining arguments give a command and its arguments to exe‐
348 cute with standard input, standard output and standard error
349 redirected to the file descriptor on which the TCP session has
350 been accepted. If no command is given, a new zsh is started.
351 This gives everyone on your network direct access to your ac‐
352 count, which in many cases will be a bad thing.
353 The command is run in the background, so tcp_proxy can then ac‐
355 cept new connections. It continues to accept new connections
356 until interrupted.
357 tcp_spam [ -ertv ] [ -a | -s sess | -l sess[,...] ] cmd [ arg ... ]
359 Execute `cmd [ arg ... ]' for each session in turn. Note this
360 executes the command and arguments; it does not send the command
361 line as data unless the -t (transmit) option is given.
362 The sessions may be selected explicitly with the standard -a, -s
364 or -l options, or may be chosen implicitly. If none of the
365 three options is given the rules are: first, if the array
366 $tcp_spam_list is set, this is taken as the list of sessions,
367 otherwise all sessions are taken. Second, any sessions given in
368 the array $tcp_no_spam_list are removed from the list of ses‐
369 sions.
370 Normally, any sessions added by the `-a' flag or when all ses‐
372 sions are chosen implicitly are spammed in alphabetic order;
373 sessions given by the $tcp_spam_list array or on the command
374 line are spammed in the order given. The -r flag reverses the
375 order however it was arrived it.
376 The -v flag specifies that a $TCP_PROMPT will be output before
378 each session. This is output after any modification to TCP_SESS
379 by the user-defined tcp_on_spam function described below. (Ob‐
380 viously that function is able to generate its own output.)
381 If the option -e is present, the line given as `cmd [ arg ... ]'
383 is executed using eval, otherwise it is executed without any
384 further processing.
385 tcp_talk
387 This is a fairly simple-minded attempt to force input to the
388 line editor to go straight to the default TCP_SESS.
389 An escape string, $TCP_TALK_ESCAPE, default `:', is used to al‐
391 low access to normal shell operation. If it is on its own at
392 the start of the line, or followed only by whitespace, the line
393 editor returns to normal operation. Otherwise, the string and
394 any following whitespace are skipped and the remainder of the
395 line executed as shell input without any change of the line edi‐
396 tor's operating mode.
397 The current implementation is somewhat deficient in terms of use
399 of the command history. For this reason, many users will prefer
400 to use some form of alternative approach for sending data easily
401 to the current session. One simple approach is to alias some
402 special character (such as `%') to `tcp_command --'.
403 tcp_wait
405 The sole argument is an integer or floating point number which
406 gives the seconds to delay. The shell will do nothing for that
407 period except wait for input on all TCP sessions by calling
408 tcp_read -a. This is similar to the interactive behaviour at
409 the command prompt when zle handlers are installed.
410 `One-shot' file transfer
412 tcp_point port
413 tcp_shoot host port
414 This pair of functions provide a simple way to transfer a file
415 between two hosts within the shell. Note, however, that bulk
416 data transfer is currently done using cat. tcp_point reads any
417 data arriving at port and sends it to standard output; tcp_shoot
418 connects to port on host and sends its standard input. Any un‐
419 used port may be used; the standard mechanism for picking a port
420 is to think of a random four-digit number above 1024 until one
421 works.
422 To transfer a file from host woodcock to host springes, on
424 springes:
425 tcp_point 8091 >output_file
427 and on woodcock:
429 tcp_shoot springes 8091 <input_file
431 As these two functions do not require tcp_open to set up a TCP
433 connection first, they may need to be autoloaded separately.
434
436 Certain functions, if defined by the user, will be called by the func‐
437 tion system in certain contexts. This facility depends on the module
438 zsh/parameter, which is usually available in interactive shells as the
439 completion system depends on it. None of the functions need be de‐
440 fined; they simply provide convenient hooks when necessary.
441 Typically, these are called after the requested action has been taken,
443 so that the various parameters will reflect the new state.
444 tcp_on_alias alias fd
446 When an alias is defined, this function will be called with two
447 arguments: the name of the alias, and the file descriptor of the
448 corresponding session.
449 tcp_on_awol sess fd
451 If the function tcp_fd_handler is handling input from the line
452 editor and detects that the file descriptor is no longer reus‐
453 able, by default it removes it from the list of file descriptors
454 handled by this method and prints a message. If the function
455 tcp_on_awol is defined it is called immediately before this
456 point. It may return status 100, which indicates that the nor‐
457 mal handling should still be performed; any other return status
458 indicates that no further action should be taken and the
459 tcp_fd_handler should return immediately with the given status.
460 Typically the action of tcp_on_awol will be to close the ses‐
461 sion.
462 The variable TCP_INVALIDATE_ZLE will be a non-empty string if it
464 is necessary to invalidate the line editor display using `zle
465 -I' before printing output from the function.
466 (`AWOL' is military jargon for `absent without leave' or some
468 variation. It has no pre-existing technical meaning known to
469 the author.)
470 tcp_on_close sess fd
472 This is called with the name of a session being closed and the
473 file descriptor which corresponded to that session. Both will
474 be invalid by the time the function is called.
475 tcp_on_open sess fd
477 This is called after a new session has been defined with the
478 session name and file descriptor as arguments. If it returns a
479 non-zero status, opening the session is assumed to fail and the
480 session is closed again; however, tcp_open will continue to at‐
481 tempt to open any remaining sessions given on the command line.
482 tcp_on_rename oldsess fd newsess
484 This is called after a session has been renamed with the three
485 arguments old session name, file descriptor, new session name.
486 tcp_on_spam sess command ...
488 This is called once for each session spammed, just before a com‐
489 mand is executed for a session by tcp_spam. The arguments are
490 the session name followed by the command list to be executed.
491 If tcp_spam was called with the option -t, the first command
492 will be tcp_send.
493 This function is called after $TCP_SESS is set to reflect the
495 session to be spammed, but before any use of it is made. Hence
496 it is possible to alter the value of $TCP_SESS within this func‐
497 tion. For example, the session arguments to tcp_spam could in‐
498 clude extra information to be stripped off and processed in
499 tcp_on_spam.
500 If the function sets the parameter $REPLY to `done', the command
502 line is not executed; in addition, no prompt is printed for the
503 -v option to tcp_spam.
504 tcp_on_unalias alias fd
506 This is called with the name of an alias and the corresponding
507 session's file descriptor after an alias has been deleted.
508
510 The following functions are used by the TCP function system but will
511 rarely if ever need to be called directly.
512 tcp_fd_handler
514 This is the function installed by tcp_open for handling input
515 from within the line editor, if that is required. It is in the
516 format documented for the builtin `zle -F' in zshzle(1) .
517 While active, the function sets the parameter TCP_HANDLER_ACTIVE
519 to 1. This allows shell code called internally (for example, by
520 setting tcp_on_read) to tell if is being called when the shell
521 is otherwise idle at the editor prompt.
522 tcp_output [ -q ] -P prompt -F fd -S sess
524 This function is used for both logging and handling output to
525 standard output, from within tcp_read and (if $TCP_OUTPUT is
526 set) tcp_send.
527 The prompt to use is specified by -P; the default is the empty
529 string. It can contain:
530 %c Expands to 1 if the session is the current session, oth‐
531 erwise 0. Used with ternary expressions such as
532 `%(c.-.+)' to output `+' for the current session and `-'
533 otherwise.
534 %f Replaced by the session's file descriptor.
536 %s Replaced by the session name.
538 %% Replaced by a single `%'.
540 The option -q suppresses output to standard output, but not to
542 any log files which are configured.
543 The -S and -F options are used to pass in the session name and
545 file descriptor for possible replacement in the prompt.
546
548 Parameters follow the usual convention that uppercase is used for
549 scalars and integers, while lowercase is used for normal and associa‐
550 tive array. It is always safe for user code to read these parameters.
551 Some parameters may also be set; these are noted explicitly. Others
552 are included in this group as they are set by the function system for
553 the user's benefit, i.e. setting them is typically not useful but is
554 benign.
555 It is often also useful to make settable parameters local to a func‐
557 tion. For example, `local TCP_SILENT=1' specifies that data read dur‐
558 ing the function call will not be printed to standard output, regard‐
559 less of the setting outside the function. Likewise, `local
560 TCP_SESS=sess' sets a session for the duration of a function, and `lo‐
561 cal TCP_PROMPT=' specifies that no prompt is used for input during the
562 function.
563 tcp_expect_lines
565 Array. The set of lines read during the last call to tcp_ex‐
566 pect, including the last ($TCP_LINE).
567 tcp_filter
569 Array. May be set directly. A set of extended globbing patterns
570 which, if matched in tcp_output, will cause the line not to be
571 printed to standard output. The patterns should be defined as
572 described for the arguments to tcp_expect. Output of line to
573 log files is not affected.
574 TCP_HANDLER_ACTIVE
576 Scalar. Set to 1 within tcp_fd_handler to indicate to functions
577 called recursively that they have been called during an editor
578 session. Otherwise unset.
579 TCP_LINE
581 The last line read by tcp_read, and hence also tcp_expect.
582 TCP_LINE_FD
584 The file descriptor from which $TCP_LINE was read.
585 ${tcp_by_fd[$TCP_LINE_FD]} will give the corresponding session
586 name.
587 tcp_lines
589 Array. The set of lines read during the last call to tcp_read,
590 including the last ($TCP_LINE).
591 TCP_LOG
593 May be set directly, although it is also controlled by tcp_log.
594 The name of a file to which output from all sessions will be
595 sent. The output is proceeded by the usual $TCP_PROMPT. If it
596 is not an absolute path name, it will follow the user's current
597 directory.
598 TCP_LOG_SESS
600 May be set directly, although it is also controlled by tcp_log.
601 The prefix for a set of files to which output from each session
602 separately will be sent; the full filename is
603 ${TCP_LOG_SESS}.sess. Output to each file is raw; no prompt is
604 added. If it is not an absolute path name, it will follow the
605 user's current directory.
606 tcp_no_spam_list
608 Array. May be set directly. See tcp_spam for how this is used.
609 TCP_OUTPUT
611 May be set directly. If a non-empty string, any data sent to a
612 session by tcp_send will be logged. This parameter gives the
613 prompt to be used in a file specified by $TCP_LOG but not in a
614 file generated from $TCP_LOG_SESS. The prompt string has the
615 same format as TCP_PROMPT and the same rules for its use apply.
616 TCP_PROMPT
618 May be set directly. Used as the prefix for data read by
619 tcp_read which is printed to standard output or to the log file
620 given by $TCP_LOG, if any. Any `%s', `%f' or `%%' occurring in
621 the string will be replaced by the name of the session, the ses‐
622 sion's underlying file descriptor, or a single `%', respec‐
623 tively. The expression `%c' expands to 1 if the session being
624 read is the current session, else 0; this is most useful in
625 ternary expressions such as `%(c.-.+)' which outputs `+' if the
626 session is the current one, else `-'.
627 If the prompt starts with %P, this is stripped and the complete
629 result of the previous stage is passed through standard prompt
630 %-style formatting before being output.
631 TCP_READ_DEBUG
633 May be set directly. If this has non-zero length, tcp_read will
634 give some limited diagnostics about data being read.
635 TCP_SECONDS_START
637 This value is created and initialised to zero by tcp_open.
638 The functions tcp_read and tcp_expect use the shell's SECONDS
640 parameter for their own timing purposes. If that parameter is
641 not of floating point type on entry to one of the functions, it
642 will create a local parameter SECONDS which is floating point
643 and set the parameter TCP_SECONDS_START to the previous value of
644 $SECONDS. If the parameter is already floating point, it is
645 used without a local copy being created and TCP_SECONDS_START is
646 not set. As the global value is zero, the shell elapsed time is
647 guaranteed to be the sum of $SECONDS and $TCP_SECONDS_START.
648 This can be avoided by setting SECONDS globally to a floating
650 point value using `typeset -F SECONDS'; then the TCP functions
651 will never make a local copy and never set TCP_SECONDS_START to
652 a non-zero value.
653 TCP_SESS
655 May be set directly. The current session; must refer to one of
656 the sessions established by tcp_open.
657 TCP_SILENT
659 May be set directly, although it is also controlled by tcp_log.
660 If of non-zero length, data read by tcp_read will not be written
661 to standard output, though may still be written to a log file.
662 tcp_spam_list
664 Array. May be set directly. See the description of the func‐
665 tion tcp_spam for how this is used.
666 TCP_TALK_ESCAPE
668 May be set directly. See the description of the function
669 tcp_talk for how this is used.
670 TCP_TIMEOUT
672 May be set directly. Currently this is only used by the func‐
673 tion tcp_command, see above.
674
676 The following parameters are not set by the function system, but have a
677 special effect if set by the user.
678 tcp_on_read
680 This should be an associative array; if it is not, the behaviour
681 is undefined. Each key is the name of a shell function or other
682 command, and the corresponding value is a shell pattern (using
683 EXTENDED_GLOB). Every line read from a TCP session directly or
684 indirectly using tcp_read (which includes lines read by tcp_ex‐
685 pect) is compared against the pattern. If the line matches, the
686 command given in the key is called with two arguments: the name
687 of the session from which the line was read, and the line it‐
688 self.
689 If any function called to handle a line returns a non-zero sta‐
691 tus, the line is not output. Thus a tcp_on_read handler con‐
692 taining only the instruction `return 1' can be used to suppress
693 output of particular lines (see, however, tcp_filter above).
694 However, the line is still stored in TCP_LINE and tcp_lines;
695 this occurs after all tcp_on_read processing.
696
698 These parameters are controlled by the function system; they may be
699 read directly, but should not usually be set by user code.
700 tcp_aliases
702 Associative array. The keys are the names of sessions estab‐
703 lished with tcp_open; each value is a space-separated list of
704 aliases which refer to that session.
705 tcp_by_fd
707 Associative array. The keys are session file descriptors; each
708 value is the name of that session.
709 tcp_by_name
711 Associative array. The keys are the names of sessions; each
712 value is the file descriptor associated with that session.
713
715 Here is a trivial example using a remote calculator.
716 To create a calculator server on port 7337 (see the dc manual page for
718 quite how infuriating the underlying command is):
719 tcp_proxy 7337 dc
721 To connect to this from the same host with a session also named `dc':
723 tcp_open localhost 7337 dc
725 To send a command to the remote session and wait a short while for out‐
727 put (assuming dc is the current session):
728 tcp_command 2 4 + p
730 To close the session:
732 tcp_close
734 The tcp_proxy needs to be killed to be stopped. Note this will not
736 usually kill any connections which have already been accepted, and also
737 that the port is not immediately available for reuse.
738 The following chunk of code puts a list of sessions into an xterm
740 header, with the current session followed by a star.
741 print -n "\033]2;TCP:" ${(k)tcp_by_name:/$TCP_SESS/$TCP_SESS\*} "\a"
743
745 The function tcp_read uses the shell's normal read builtin. As this
746 reads a complete line at once, data arriving without a terminating new‐
747 line can cause the function to block indefinitely.
748 Though the function suite works well for interactive use and for data
750 arriving in small amounts, the performance when large amounts of data
751 are being exchanged is likely to be extremely poor.
752zsh 5.9 May 14, 2022 ZSHTCPSYS(1)