1ZSHTCPSYS(1)                General Commands Manual               ZSHTCPSYS(1)
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NAME

6       zshtcpsys - zsh tcp system
7

DESCRIPTION

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
19       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
28       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

TCP USER FUNCTIONS

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
41              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
50              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
62              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
74              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
82              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
86              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
100              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
105              The function tcp_on_open, if defined, is called when  a  session
106              is opened.  See the description below.
107
108       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
114              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
118              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
125              If  the  option  -q  is given, no informational messages will be
126              printed.
127
128
129       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
139              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
152              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
157              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
163              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
170              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
174              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
177              See tcp_log for how to control where data is sent by tcp_read.
178
179       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
187              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
192              The  option  -n  prevents tcp_send from putting a newline at the
193              end of the data strings.
194
195              The remaining options all behave as for tcp_read.
196
197              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
200              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
205   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
211              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
215              The second form lists any aliases specified, or all  aliases  if
216              none.
217
218              The  third  form deletes all the aliases listed.  The underlying
219              sessions are not affected.
220
221              The option -q suppresses an inconsistently chosen subset of  er‐
222              ror messages.
223
224       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
230              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
237              The  option -c closes all logging, both complete and per-session
238              logs.
239
240              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
244              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
248       tcp_rename old new
249              Rename session old to session new.  The  old  name  becomes  in‐
250              valid.
251
252       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
259              With  a sess argument, set the current session to sess.  This is
260              equivalent to changing $TCP_SESS directly.
261
262              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
268   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
276              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
281
282       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
291              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
295              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
305              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
312              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
321              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
329              The option -q is passed directly down to tcp_read.
330
331              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
337       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
344              The first argument is a TCP port on which the function will lis‐
345              ten.
346
347              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
354              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
358       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
363              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
371              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
377              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
382              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
386       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
390              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
398              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
404       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
411   `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
423              To  transfer  a  file  from  host  woodcock to host springes, on
424              springes:
425
426                     tcp_point 8091 >output_file
427
428              and on woodcock:
429
430                     tcp_shoot springes 8091 <input_file
431
432              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

TCP USER-DEFINED FUNCTIONS

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
442       Typically,  these are called after the requested action has been taken,
443       so that the various parameters will reflect the new state.
444
445       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
450       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
463              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
467              (`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
471       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
476       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
483       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
487       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
494              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
501              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
505       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

TCP UTILITY FUNCTIONS

510       The  following  functions  are used by the TCP function system but will
511       rarely if ever need to be called directly.
512
513       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
518              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
523       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
528              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
535              %f     Replaced by the session's file descriptor.
536
537              %s     Replaced by the session name.
538
539              %%     Replaced by a single `%'.
540
541              The  option  -q suppresses output to standard output, but not to
542              any log files which are configured.
543
544              The -S and -F options are used to pass in the session  name  and
545              file descriptor for possible replacement in the prompt.
546

TCP USER PARAMETERS

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
556       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
564       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
568       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
575       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
580       TCP_LINE
581              The last line read by tcp_read, and hence also tcp_expect.
582
583       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
588       tcp_lines
589              Array. The set of lines read during the last call  to  tcp_read,
590              including the last ($TCP_LINE).
591
592       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
599       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
607       tcp_no_spam_list
608              Array.  May be set directly.  See tcp_spam for how this is used.
609
610       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
617       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
628              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
632       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
636       TCP_SECONDS_START
637              This value is created and initialised to zero by tcp_open.
638
639              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
649              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
654       TCP_SESS
655              May be set directly.  The current session; must refer to one  of
656              the sessions established by tcp_open.
657
658       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
663       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
667       TCP_TALK_ESCAPE
668              May be set  directly.   See  the  description  of  the  function
669              tcp_talk for how this is used.
670
671       TCP_TIMEOUT
672              May  be  set directly.  Currently this is only used by the func‐
673              tion tcp_command, see above.
674

TCP USER-DEFINED PARAMETERS

676       The following parameters are not set by the function system, but have a
677       special effect if set by the user.
678
679       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
690              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

TCP UTILITY PARAMETERS

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
701       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
706       tcp_by_fd
707              Associative  array.  The keys are session file descriptors; each
708              value is the name of that session.
709
710       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

TCP EXAMPLES

715       Here is a trivial example using a remote calculator.
716
717       To  create a calculator server on port 7337 (see the dc manual page for
718       quite how infuriating the underlying command is):
719
720              tcp_proxy 7337 dc
721
722       To connect to this from the same host with a session also named `dc':
723
724              tcp_open localhost 7337 dc
725
726       To send a command to the remote session and wait a short while for out‐
727       put (assuming dc is the current session):
728
729              tcp_command 2 4 + p
730
731       To close the session:
732
733              tcp_close
734
735       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
739       The  following  chunk  of  code  puts  a list of sessions into an xterm
740       header, with the current session followed by a star.
741
742              print -n "\033]2;TCP:" ${(k)tcp_by_name:/$TCP_SESS/$TCP_SESS\*} "\a"
743

TCP BUGS

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
749       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.
752
753
754
755zsh 5.9                          May 14, 2022                     ZSHTCPSYS(1)
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