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. 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
67 $REPLY. 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
115 unset, 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
120 directly from the command line. If the option -n is given, no
121 attempt will be made to close file descriptors in this case.
122 The -n option is not used for genuine ztcp session; the file
123 descriptors 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 ]
129 [ -a | -u fd ... | -l sess,... | -s sess ...]
130 Perform a read operation on the current session, or on a list of
131 sessions if any are given with -u, -l or -s, or all open ses‐
132 sions if the option -a is given. Any of the -u, -l or -s
133 options may be repeated or mixed together. The -u option speci‐
134 fies a file descriptor directly (only those managed by this sys‐
135 tem are useful), the other two specify sessions as described for
136 tcp_open above.
137 The function checks for new data available on all the sessions
139 listed. Unless the -b option is given, it will not block wait‐
140 ing for new data. Any one line of data from any of the avail‐
141 able sessions will be read, stored in the parameter $TCP_LINE,
142 and displayed to standard output unless $TCP_SILENT contains a
143 non-empty string. When printed to standard output the string
144 $TCP_PROMPT will be shown at the start of the line; the default
145 form for this includes the name of the session being read. See
146 below for more information on these parameters. In this mode,
147 tcp_read can be called repeatedly until it returns status 2
148 which indicates all pending input from all specified sessions
149 has been handled.
150 With the option -b, equivalent to an infinite timeout, the func‐
152 tion will block until a line is available to read from one of
153 the specified sessions. However, only a single line is
154 returned.
155 The option -d indicates that all pending input should be
157 drained. In this case tcp_read may process multiple lines in
158 the manner given above; only the last is stored in $TCP_LINE,
159 but the complete set is stored in the array $tcp_lines. This is
160 cleared at the start of each call to tcp_read.
161 The options -t and -T specify a timeout in seconds, which may be
163 a floating point number for increased accuracy. With -t the
164 timeout is applied before each line read. With -T, the timeout
165 applies to the overall operation, possibly including multiple
166 read operations if the option -d is present; without this
167 option, there is no distinction between -t and -T.
168 The function does not print informational messages, but if the
170 option -q is given, no error message is printed for a non-exis‐
171 tent session.
172 A return status of 2 indicates a timeout or no data to read.
174 Any other non-zero return status indicates some error condition.
175 See tcp_log for how to control where data is sent by tcp_read.
177 tcp_send [-cnq] [ -s sess | -l sess,... ] data ...
179 tcp_send [-cnq] -a data ...
180 Send the supplied data strings to all the specified sessions in
181 turn. The underlying operation differs little from a `print -r'
182 to the session's file descriptor, although it attempts to pre‐
183 vent the shell from dying owing to a SIGPIPE caused by an
184 attempt to write to a defunct session.
185 The option -c causes tcp_send to behave like cat. It reads
187 lines from standard input until end of input and sends them in
188 turn to the specified session(s) exactly as if they were given
189 as data arguments to individual tcp_send commands.
190 The option -n prevents tcp_send from putting a newline at the
192 end of the data strings.
193 The remaining options all behave as for tcp_read.
195 The data arguments are not further processed once they have been
197 passed to tcp_send; they are simply passed down to print -r.
198 If the parameter $TCP_OUTPUT is a non-empty string and logging
200 is enabled then the data sent to each session will be echoed to
201 the log file(s) with $TCP_OUTPUT in front where appropriate,
202 much in the manner of $TCP_PROMPT.
203 Session Management
205 tcp_alias [-q] alias=sess ...
206 tcp_alias [-q] [ alias ] ...
207 tcp_alias -d [-q] alias ...
208 This function is not particularly well tested.
209 The first form creates an alias for a session name; alias can
211 then be used to refer to the existing session sess. As many
212 aliases may be listed as required.
213 The second form lists any aliases specified, or all aliases if
215 none.
216 The third form deletes all the aliases listed. The underlying
218 sessions are not affected.
219 The option -q suppresses an inconsistently chosen subset of
221 error messages.
222 tcp_log [-asc] [ -n | -N ] [ logfile ]
224 With an argument logfile, all future input from tcp_read will be
225 logged to the named file. Unless -a (append) is given, this
226 file will first be truncated or created empty. With no argu‐
227 ments, show the current status of logging.
228 With the option -s, per-session logging is enabled. Input from
230 tcp_read is output to the file logfile.sess. As the session is
231 automatically discriminated by the filename, the contents are
232 raw (no $TCP_PROMPT). The option -a applies as above.
233 Per-session logging and logging of all data in one file are not
234 mutually exclusive.
235 The option -c closes all logging, both complete and per-session
237 logs.
238 The options -n and -N respectively turn off or restore output of
240 data read by tcp_read to standard output; hence `tcp_log -cn'
241 turns off all output by tcp_read.
242 The function is purely a convenient front end to setting the
244 parameters $TCP_LOG, $TCP_LOG_SESS, $TCP_SILENT, which are
245 described below.
246 tcp_rename old new
248 Rename session old to session new. The old name becomes
249 invalid.
250 tcp_sess [ sess [ command ... ] ]
252 With no arguments, list all the open sessions and associated
253 file descriptors. The current session is marked with a star.
254 For use in functions, direct access to the parameters
255 $tcp_by_name, $tcp_by_fd and $TCP_SESS is probably more conve‐
256 nient; see below.
257 With a sess argument, set the current session to sess. This is
259 equivalent to changing $TCP_SESS directly.
260 With additional arguments, temporarily set the current session
262 while executing the string command .... The first argument is
263 re-evaluated so as to expand aliases etc., but the remaining
264 arguments are passed through as the appear to tcp_sess. The
265 original session is restored when tcp_sess exits.
266 Advanced I/O
268 tcp_command send-options ... send-arguments ...
269 This is a convenient front-end to tcp_send. All arguments are
270 passed to tcp_send, then the function pauses waiting for data.
271 While data is arriving at least every $TCP_TIMEOUT (default 0.3)
272 seconds, data is handled and printed out according to the cur‐
273 rent settings. Status 0 is always returned.
274 This is generally only useful for interactive use, to prevent
276 the display becoming fragmented by output returned from the con‐
277 nection. Within a programme or function it is generally better
278 to handle reading data by a more explicit method.
279 tcp_expect [ -q ] [ -p var ] [ -t to | -T TO]
281 [ -a | -s sess ... | -l sess,... ] pattern ...
282 Wait for input matching any of the given patterns from any of
283 the specified sessions. Input is ignored until an input line
284 matches one of the given patterns; at this point status zero is
285 returned, the matching line is stored in $TCP_LINE, and the full
286 set of lines read during the call to tcp_expect is stored in the
287 array $tcp_expect_lines.
288 Sessions are specified in the same way as tcp_read: the default
290 is to use the current session, otherwise the sessions specified
291 by -a, -s, or -l are used.
292 Each pattern is a standard zsh extended-globbing pattern; note
294 that it needs to be quoted to avoid it being expanded immedi‐
295 ately by filename generation. It must match the full line, so
296 to match a substring there must be a `*' at the start and end.
297 The line matched against includes the $TCP_PROMPT added by
298 tcp_read. It is possible to include the globbing flags `#b' or
299 `#m' in the patterns to make backreferences available in the
300 parameters $MATCH, $match, etc., as described in the base zsh
301 documentation on pattern matching.
302 Unlike tcp_read, the default behaviour of tcp_expect is to block
304 indefinitely until the required input is found. This can be
305 modified by specifying a timeout with -t or -T; these function
306 as in tcp_read, specifying a per-read or overall timeout,
307 respectively, in seconds, as an integer or floating-point num‐
308 ber. As tcp_read, the function returns status 2 if a timeout
309 occurs.
310 The function returns as soon as any one of the patterns given
312 match. If the caller needs to know which of the patterns
313 matched, the option -p var can be used; on return, $var is set
314 to the number of the pattern using ordinary zsh indexing, i.e.
315 the first is 1, and so on. Note the absence of a `$' in front
316 of var. To avoid clashes, the parameter cannot begin with
317 `_expect'.
318 The option -q is passed directly down to tcp_read.
320 As all input is done via tcp_read, all the usual rules about
322 output of lines read apply. One exception is that the parameter
323 $tcp_lines will only reflect the line actually matched by
324 tcp_expect; use $tcp_expect_lines for the full set of lines read
325 during the function call.
326 tcp_proxy
328 This is a simple-minded function to accept a TCP connection and
329 execute a command with I/O redirected to the connection.
330 Extreme caution should be taken as there is no security whatso‐
331 ever and this can leave your computer open to the world. Ide‐
332 ally, it should only be used behind a firewall.
333 The first argument is a TCP port on which the function will lis‐
335 ten.
336 The remaining arguments give a command and its arguments to exe‐
338 cute with standard input, standard output and standard error
339 redirected to the file descriptor on which the TCP session has
340 been accepted. If no command is given, a new zsh is started.
341 This gives everyone on your network direct access to your
342 account, which in many cases will be a bad thing.
343 The command is run in the background, so tcp_proxy can then
345 accept new connections. It continues to accept new connections
346 until interrupted.
347 tcp_spam [-ertv] [ -a | -s sess | -l sess,... ] cmd ...
349 Execute `cmd ...' for each session in turn. Note this executes
350 the command and arguments; it does not send the command line as
351 data unless the -t (transmit) option is given.
352 The sessions may be selected explicitly with the standard -a, -s
354 or -l options, or may be chosen implicitly. If none of the
355 three options is given the rules are: first, if the array
356 $tcp_spam_list is set, this is taken as the list of sessions,
357 otherwise all sessions are taken. Second, any sessions given in
358 the array $tcp_no_spam_list are removed from the list of ses‐
359 sions.
360 Normally, any sessions added by the `-a' flag or when all ses‐
362 sions are chosen implicitly are spammed in alphabetic order;
363 sessions given by the $tcp_spam_list array or on the command
364 line are spammed in the order given. The -r flag reverses the
365 order however it was arrived it.
366 The -v flag specifies that a $TCP_PROMPT will be output before
368 each session. This is output after any modification to TCP_SESS
369 by the user-defined tcp_on_spam function described below.
370 (Obviously that function is able to generate its own output.)
371 If the option -e is present, the line given as cmd ... is exe‐
373 cuted using eval, otherwise it is executed without any further
374 processing.
375 tcp_talk
377 This is a fairly simple-minded attempt to force input to the
378 line editor to go straight to the default TCP_SESSION.
379 An escape string, $TCP_TALK_ESCAPE, default `:', is used to
381 allow access to normal shell operation. If it is on its own at
382 the start of the line, or followed only by whitespace, the line
383 editor returns to normal operation. Otherwise, the string and
384 any following whitespace are skipped and the remainder of the
385 line executed as shell input without any change of the line edi‐
386 tor's operating mode.
387 The current implementation is somewhat deficient in terms of use
389 of the command history. For this reason, many users will prefer
390 to use some form of alternative approach for sending data easily
391 to the current session. One simple approach is to alias some
392 special character (such as `%') to `tcp_command --'.
393 tcp_wait
395 The sole argument is an integer or floating point number which
396 gives the seconds to delay. The shell will do nothing for that
397 period except wait for input on all TCP sessions by calling
398 tcp_read -a. This is similar to the interactive behaviour at
399 the command prompt when zle handlers are installed.
400 `One-shot' file transfer
402 tcp_point port
403 tcp_shoot host port
404 This pair of functions provide a simple way to transfer a file
405 between two hosts within the shell. Note, however, that bulk
406 data transfer is currently done using cat. tcp_point reads any
407 data arriving at port and sends it to standard output; tcp_shoot
408 connects to port on host and sends its standard input. Any
409 unused port may be used; the standard mechanism for picking a
410 port is to think of a random four-digit number above 1024 until
411 one works.
412 To transfer a file from host woodcock to host springes, on
414 springes:
415 tcp_point 8091 >output_file
417 and on woodcock:
419 tcp_shoot springes 8091 <input_file
421 As these two functions do not require tcp_open to set up a TCP
423 connection first, they may need to be autoloaded separately.
424
426 Certain functions, if defined by the user, will be called by the func‐
427 tion system in certain contexts. This facility depends on the module
428 zsh/parameter, which is usually available in interactive shells as the
429 completion system depends on it. None of the functions need be
430 defined; they simply provide convenient hooks when necessary.
431 Typically, these are called after the requested action has been taken,
433 so that the various parameters will reflect the new state.
434 tcp_on_alias alias fd
436 When an alias is defined, this function will be called with two
437 arguments: the name of the alias, and the file descriptor of the
438 corresponding session.
439 tcp_on_awol sess fd
441 If the function tcp_fd_handler is handling input from the line
442 editor and detects that the file descriptor is no longer reus‐
443 able, by default it removes it from the list of file descriptors
444 handled by this method and prints a message. If the function
445 tcp_on_awol is defined it is called immediately before this
446 point. It may return status 100, which indicates that the nor‐
447 mal handling should still be performed; any other return status
448 indicates that no further action should be taken and the
449 tcp_fd_handler should return immediately with the given status.
450 Typically the action of tcp_on_awol will be to close the ses‐
451 sion.
452 The variable TCP_INVALIDATE_ZLE will be a non-empty string if it
454 is necessary to invalidate the line editor display using `zle
455 -I' before printing output from the function.
456 (`AWOL' is military jargon for `absent without leave' or some
458 variation. It has no pre-existing technical meaning known to
459 the author.)
460 tcp_on_close sess fd
462 This is called with the name of a session being closed and the
463 file descriptor which corresponded to that session. Both will
464 be invalid by the time the function is called.
465 tcp_on_open sess fd
467 This is called after a new session has been defined with the
468 session name and file descriptor as arguments. If it returns a
469 non-zero status, opening the session is assumed to fail and the
470 session is closed again; however, tcp_open will continue to
471 attempt to open any remaining sessions given on the command
472 line.
473 tcp_on_rename oldsess fd newsess
475 This is called after a session has been renamed with the three
476 arguments old session name, file descriptor, new session name.
477 tcp_on_spam sess command ...
479 This is called once for each session spammed, just before a com‐
480 mand is executed for a session by tcp_spam. The arguments are
481 the session name followed by the command list to be executed.
482 If tcp_spam was called with the option -t, the first command
483 will be tcp_send.
484 This function is called after $TCP_SESS is set to reflect the
486 session to be spammed, but before any use of it is made. Hence
487 it is possible to alter the value of $TCP_SESS within this func‐
488 tion. For example, the session arguments to tcp_spam could
489 include extra information to be stripped off and processed in
490 tcp_on_spam.
491 If the function sets the parameter $REPLY to `done', the command
493 line is not executed; in addition, no prompt is printed for the
494 -v option to tcp_spam.
495 tcp_on_unalias alias fd
497 This is called with the name of an alias and the corresponding
498 session's file descriptor after an alias has been deleted.
499
501 The following functions are used by the TCP function system but will
502 rarely if ever need to be called directly.
503 tcp_fd_handler
505 This is the function installed by tcp_open for handling input
506 from within the line editor, if that is required. It is in the
507 format documented for the builtin `zle -F' in zshzle(1) .
508 While active, the function sets the parameter TCP_HANDLER_ACTIVE
510 to 1. This allows shell code called internally (for example, by
511 setting tcp_on_read) to tell if is being called when the shell
512 is otherwise idle at the editor prompt.
513 tcp_output [ -q ] -P prompt -F fd -S sess
515 This function is used for both logging and handling output to
516 standard output, from within tcp_read and (if $TCP_OUTPUT is
517 set) tcp_send.
518 The prompt to use is specified by -P; the default is the empty
520 string. It can contain:
521 %c Expands to 1 if the session is the current session, oth‐
522 erwise 0. Used with ternary expressions such as
523 `%(c.-.+)' to output `+' for the current session and `-'
524 otherwise.
525 %f Replaced by the session's file descriptor.
527 %s Replaced by the session name.
529 %% Replaced by a single `%'.
531 The option -q suppresses output to standard output, but not to
533 any log files which are configured.
534 The -S and -F options are used to pass in the session name and
536 file descriptor for possible replacement in the prompt.
537
539 Parameters follow the usual convention that uppercase is used for
540 scalars and integers, while lowercase is used for normal and associa‐
541 tive array. It is always safe for user code to read these parameters.
542 Some parameters may also be set; these are noted explicitly. Others
543 are included in this group as they are set by the function system for
544 the user's benefit, i.e. setting them is typically not useful but is
545 benign.
546 It is often also useful to make settable parameters local to a func‐
548 tion. For example, `local TCP_SILENT=1' specifies that data read dur‐
549 ing the function call will not be printed to standard output, regard‐
550 less of the setting outside the function. Likewise, `local
551 TCP_SESS=sess' sets a session for the duration of a function, and
552 `local TCP_PROMPT=' specifies that no prompt is used for input during
553 the function.
554 tcp_expect_lines
556 Array. The set of lines read during the last call to
557 tcp_expect, including the last ($TCP_LINE).
558 tcp_filter
560 Array. May be set directly. A set of extended globbing patterns
561 which, if matched in tcp_output, will cause the line not to be
562 printed to standard output. The patterns should be defined as
563 described for the arguments to tcp_expect. Output of line to
564 log files is not affected.
565 TCP_HANDLER_ACTIVE
567 Scalar. Set to 1 within tcp_fd_handler to indicate to functions
568 called recursively that they have been called during an editor
569 session. Otherwise unset.
570 TCP_LINE
572 The last line read by tcp_read, and hence also tcp_expect.
573 TCP_LINE_FD
575 The file descriptor from which $TCP_LINE was read.
576 ${tcp_by_fd[$TCP_LINE_FD]} will give the corresponding session
577 name.
578 tcp_lines
580 Array. The set of lines read during the last call to tcp_read,
581 including the last ($TCP_LINE).
582 TCP_LOG
584 May be set directly, although it is also controlled by tcp_log.
585 The name of a file to which output from all sessions will be
586 sent. The output is proceeded by the usual $TCP_PROMPT. If it
587 is not an absolute path name, it will follow the user's current
588 directory.
589 TCP_LOG_SESS
591 May be set directly, although it is also controlled by tcp_log.
592 The prefix for a set of files to which output from each session
593 separately will be sent; the full filename is
594 ${TCP_LOG_SESS}.sess. Output to each file is raw; no prompt is
595 added. If it is not an absolute path name, it will follow the
596 user's current directory.
597 tcp_no_spam_list
599 Array. May be set directly. See tcp_spam for how this is used.
600 TCP_OUTPUT
602 May be set directly. If a non-empty string, any data sent to a
603 session by tcp_send will be logged. This parameter gives the
604 prompt to be used in a file specified by $TCP_LOG but not in a
605 file generated from $TCP_LOG_SESS. The prompt string has the
606 same format as TCP_PROMPT and the same rules for its use apply.
607 TCP_PROMPT
609 May be set directly. Used as the prefix for data read by
610 tcp_read which is printed to standard output or to the log file
611 given by $TCP_LOG, if any. Any `%s', `%f' or `%%' occurring in
612 the string will be replaced by the name of the session, the ses‐
613 sion's underlying file descriptor, or a single `%', respec‐
614 tively. The expression `%c' expands to 1 if the session being
615 read is the current session, else 0; this is most useful in
616 ternary expressions such as `%(c.-.+)' which outputs `+' if the
617 session is the current one, else `-'.
618 TCP_READ_DEBUG
620 May be set directly. If this has non-zero length, tcp_read will
621 give some limited diagnostics about data being read.
622 TCP_SECONDS_START
624 This value is created and initialised to zero by tcp_open.
625 The functions tcp_read and tcp_expect use the shell's SECONDS
627 parameter for their own timing purposes. If that parameter is
628 not of floating point type on entry to one of the functions, it
629 will create a local parameter SECONDS which is floating point
630 and set the parameter TCP_SECONDS_START to the previous value of
631 $SECONDS. If the parameter is already floating point, it is
632 used without a local copy being created and TCP_SECONDS_START is
633 not set. As the global value is zero, the shell elapsed time is
634 guaranteed to be the sum of $SECONDS and $TCP_SECONDS_START.
635 This can be avoided by setting SECONDS globally to a floating
637 point value using `typeset -F SECONDS'; then the TCP functions
638 will never make a local copy and never set TCP_SECONDS_START to
639 a non-zero value.
640 TCP_SESS
642 May be set directly. The current session; must refer to one of
643 the sessions established by tcp_open.
644 TCP_SILENT
646 May be set directly, although it is also controlled by tcp_log.
647 If of non-zero length, data read by tcp_read will not be written
648 to standard output, though may still be written to a log file.
649 tcp_spam_list
651 Array. May be set directly. See the description of the func‐
652 tion tcp_spam for how this is used.
653 TCP_TALK_ESCAPE
655 May be set directly. See the description of the function
656 tcp_talk for how this is used.
657 TCP_TIMEOUT
659 May be set directly. Currently this is only used by the func‐
660 tion tcp_command, see above.
661
663 The following parameters are not set by the function system, but have a
664 special effect if set by the user.
665 tcp_on_read
667 This should be an associative array; if it is not, the behaviour
668 is undefined. Each key is the name of a shell function or other
669 command, and the corresponding value is a shell pattern (using
670 EXTENDED_GLOB). Every line read from a TCP session directly or
671 indirectly using tcp_read (which includes lines read by
672 tcp_expect) is compared against the pattern. If the line
673 matches, the command given in the key is called with two argu‐
674 ments: the name of the session from which the line was read, and
675 the line itself.
676 If any function called to handle a line returns a non-zero sta‐
678 tus, the line is not output. Thus a tcp_on_read handler con‐
679 taining only the instruction `return 1' can be used to suppress
680 output of particular lines (see, however, tcp_filter above).
681 However, the line is still stored in TCP_LINE and tcp_lines;
682 this occurs after all tcp_on_read processing.
683
685 These parameters are controlled by the function system; they may be
686 read directly, but should not usually be set by user code.
687 tcp_aliases
689 Associative array. The keys are the names of sessions estab‐
690 lished with tcp_open; each value is a space-separated list of
691 aliases which refer to that session.
692 tcp_by_fd
694 Associative array. The keys are session file descriptors; each
695 value is the name of that session.
696 tcp_by_name
698 Associative array. The keys are the names of sessions; each
699 value is the file descriptor associated with that session.
700
702 Here is a trivial example using a remote calculator.
703 TO create a calculator server on port 7337 (see the dc manual page for
705 quite how infuriating the underlying command is):
706 tcp_proxy 7337 dc
708 To connect to this from the same host with a session also named `dc':
710 tcp_open localhost 7337 dc
712 To send a command to the remote session and wait a short while for out‐
714 put (assuming dc is the current session):
715 tcp_command 2 4 + p
717 To close the session:
719 tcp_close
721 The tcp_proxy needs to be killed to be stopped. Note this will not
723 usually kill any connections which have already been accepted, and also
724 that the port is not immediately available for reuse.
725 The following chunk of code puts a list of sessions into an xterm
727 header, with the current session followed by a star.
728 print -n "\033]2;TCP:" ${(k)tcp_by_name:/$TCP_SESS/$TCP_SESS\*} "\a"
730
732 The function tcp_read uses the shell's normal read builtin. As this
733 reads a complete line at once, data arriving without a terminating new‐
734 line can cause the function to block indefinitely.
735 Though the function suite works well for interactive use and for data
737 arriving in small amounts, the performance when large amounts of data
738 are being exchanged is likely to be extremely poor.
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