Spec-Zone .ru
спецификации, руководства, описания, API
Spec-Zone .ru
спецификации, руководства, описания, API
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ZSHTCPSYS(1)                                                                                    ZSHTCPSYS(1)



NAME
       zshtcpsys - zsh tcp system

DESCRIPTION
       A  module  zsh/net/tcp  is provided to provide network I/O over TCP/IP from within the shell; see its
       description in zshmodules(1) .  This manual page describes a function suite based on the module.   If
       the  module  is  installed,  the functions are usually installed at the same time, in which case they
       will be available for  autoloading  in  the  default  function  search  path.   In  addition  to  the
       zsh/net/tcp  module,  the  zsh/zselect  module is used to implement timeouts on read operations.  For
       troubleshooting tips, consult the corresponding advice for the zftp functions described  in  zshzftp-sys(1) zshzftpsys(1)
       sys(1) .

       There  are  functions  corresponding  to  the  basic I/O operations open, close, read and send, named
       tcp_open etc., as well as a function tcp_expect for pattern match analysis of  data  read  as  input.
       The  system  makes it easy to receive data from and send data to multiple named sessions at once.  In
       addition, it can be linked with the shell's line editor in such a way that input  data  is  automati-cally automatically
       cally  shown  at  the  terminal.  Other facilities available including logging, filtering and config-urable configurable
       urable output prompts.

       To use the system where it is available, it should be  enough  to  `autoload  -U  tcp_open'  and  run
       tcp_open  as  documented below to start a session.  The tcp_open function will autoload the remaining
       functions.



TCP USER FUNCTIONS
   Basic I/O
       tcp_open [-qz] host port [ sess ]
       tcp_open [-qz] [ -s sess | -l sess,... ] ...
       tcp_open [-qz] [-a fd | -f fd ] [ sess ]
              Open a new session.  In the first and simplest form, open a TCP connection  to  host  host  at
              port port; numeric and symbolic forms are understood for both.

              If  sess is given, this becomes the name of the session which can be used to refer to multiple
              different TCP connections.  If sess is not given, the function  will  invent  a  numeric  name
              value (note this is not the same as the file descriptor to which the session is attached).  It
              is recommended that session names not include `funny' characters, where funny  characters  are
              not  well-defined  but certainly do not include alphanumerics or underscores, and certainly do
              include whitespace.

              In the second case, one or more sessions to be opened are given by  name.   A  single  session
              name  is  given  after -s and a comma-separated list after -l; both options may be repeated as
              many times as necessary.  A failure to open any session causes tcp_open to  abort.   The  host
              and  port  are  read from the file .ztcp_sessions in the same directory as the user's zsh ini-tialisation initialisation
              tialisation files, i.e. usually the home directory, but $ZDOTDIR if that  is  set.   The  file
              consists  of  lines  each  giving  a session name and the corresponding host and port, in that
              order (note the session name comes first, not last), separated by whitespace.

              The third form allows passive and fake TCP connections.  If the option -a is used,  its  argu-ment argument
              ment  is  a file descriptor open for listening for connections.  No function front-end is pro-vided provided
              vided to open such a file descriptor, but a call to `ztcp -l port' will create  one  with  the
              file  descriptor  stored in the parameter $REPLY.  The listening port can be closed with `ztcp
              -c fd'.  A call to `tcp_open -a fd' will block until a remote TCP connection is made  to  port
              on  the  local  machine.   At this point, a session is created in the usual way and is largely
              indistinguishable from an active connection created with one of the first two forms.

              If the option -f is used, its argument is a file descriptor which is used directly  as  if  it
              were a TCP session.  How well the remainder of the TCP function system copes with this depends
              on what actually underlies this file descriptor.  A regular file is likely to be  unusable;  a
              FIFO (pipe) of some sort will work better, but note that it is not a good idea for two differ-ent different
              ent sessions to attempt to read from the same FIFO at once.

              If the option -q is given with any of the three forms, tcp_open will not  print  informational
              messages, although it will in any case exit with an appropriate status.

              If  the  line editor (zle) is in use, which is typically the case if the shell is interactive,
              tcp_open installs a handler inside zle which will check for new data at the same  time  as  it
              checks  for  keyboard input.  This is convenient as the shell consumes no CPU time while wait-ing; waiting;
              ing; the test is performed by the operating system.  Giving the option -z to any of the  forms
              of tcp_open prevents the handler from being installed, so data must be read explicitly.  Note,
              however, this is not necessary for executing complete sets of send and read  commands  from  a
              function,  as zle is not active at this point.  Generally speaking, the handler is only active
              when the shell is waiting for input at a command prompt or in the vared builtin.   The  option
              has no effect if zle is not active; `[[ -o zle]]' will test for this.

              The first session to be opened becomes the current session and subsequent calls to tcp_open do
              not change it.  The current session is stored in the parameter $TCP_SESS; see below  for  more
              detail about the parameters used by the system.

              The function tcp_on_open, if defined, is called when a session is opened.  See the description
              below.

       tcp_close [-qn] [ -a | -l sess,... | sess ... ]
              Close the named sessions, or the current session if none is given, or all open sessions if  -a
              is  given.  The options -l and -s are both handled for consistency with tcp_open, although the
              latter is redundant.

              If the session being closed is the current one, $TCP_SESS is unset, leaving  no  current  ses-sion, session,
              sion, even if there are other sessions still open.

              If  the session was opened with tcp_open -f, the file descriptor is closed so long as it is in
              the range 0 to 9 accessible directly from the command line.  If the option  -n  is  given,  no
              attempt  will  be  made to close file descriptors in this case.  The -n option is not used for
              genuine ztcp session; the file descriptors are always closed with the session.

              If the option -q is given, no informational messages will be printed.

       tcp_read [-bdq] [ -t TO ] [ -T TO ]
           [ -a | -u fd ... | -l sess,... | -s sess ...]
              Perform a read operation on the current session, or on a list of sessions  if  any  are  given
              with  -u,  -l  or -s, or all open sessions if the option -a is given.  Any of the -u, -l or -s
              options may be repeated or mixed together.  The -u option specifies a file descriptor directly
              (only  those  managed  by this system are useful), the other two specify sessions as described
              for tcp_open above.

              The function checks for new data available on all the sessions listed.  Unless the  -b  option
              is given, it will not block waiting for new data.  Any one line of data from any of the avail-able available
              able sessions will be read, stored in the parameter $TCP_LINE, and displayed to standard  out-put output
              put  unless  $TCP_SILENT  contains  a  non-empty  string.  When printed to standard output the
              string $TCP_PROMPT will be shown at the start of the line; the default form for this  includes
              the  name  of the session being read.  See below for more information on these parameters.  In
              this mode, tcp_read can be called repeatedly until it returns status  2  which  indicates  all
              pending input from all specified sessions has been handled.

              With the option -b, equivalent to an infinite timeout, the function will block until a line is
              available to read from one of  the  specified  sessions.   However,  only  a  single  line  is
              returned.

              The  option  -d indicates that all pending input should be drained.  In this case tcp_read may
              process multiple lines in the manner given above; only the last is stored  in  $TCP_LINE,  but
              the complete set is stored in the array $tcp_lines.  This is cleared at the start of each call
              to tcp_read.

              The options -t and -T specify a timeout in seconds, which may be a floating point  number  for
              increased accuracy.  With -t the timeout is applied before each line read.  With -T, the time-out timeout
              out applies to the overall operation, possibly  including  multiple  read  operations  if  the
              option -d is present; without this option, there is no distinction between -t and -T.

              The  function  does  not print informational messages, but if the option -q is given, no error
              message is printed for a non-existent session.

              A return status of 2 indicates a timeout or no data to read.  Any other non-zero return status
              indicates some error condition.

              See tcp_log for how to control where data is sent by tcp_read.

       tcp_send [-cnq] [ -s sess | -l sess,... ] data ...
       tcp_send [-cnq] -a data ...
              Send  the  supplied data strings to all the specified sessions in turn.  The underlying opera-tion operation
              tion differs little from a `print -r' to the session's file descriptor, although  it  attempts
              to  prevent the shell from dying owing to a SIGPIPE caused by an attempt to write to a defunct
              session.

              The option -c causes tcp_send to behave like cat.  It reads lines from  standard  input  until
              end  of input and sends them in turn to the specified session(s) exactly as if they were given
              as data arguments to individual tcp_send commands.

              The option -n prevents tcp_send from putting a newline at the end of the data strings.

              The remaining options all behave as for tcp_read.

              The data arguments are not further processed once they have been passed to tcp_send; they  are
              simply passed down to print -r.

              If  the  parameter $TCP_OUTPUT is a non-empty string and logging is enabled then the data sent
              to each session will be echoed to the log file(s) with $TCP_OUTPUT in front where appropriate,
              much in the manner of $TCP_PROMPT.


   Session Management
       tcp_alias [-q] alias=sess ...
       tcp_alias [-q] [ alias ] ...
       tcp_alias -d [-q] alias ...
              This function is not particularly well tested.

              The  first  form  creates  an alias for a session name; alias can then be used to refer to the
              existing session sess.  As many aliases may be listed as required.

              The second form lists any aliases specified, or all aliases if none.

              The third form deletes all the aliases listed.  The underlying sessions are not affected.

              The option -q suppresses an inconsistently chosen subset of error messages.

       tcp_log [-asc] [ -n | -N ] [ logfile ]
              With an argument logfile, all future input from tcp_read will be logged  to  the  named  file.
              Unless  -a  (append)  is  given,  this file will first be truncated or created empty.  With no
              arguments, show the current status of logging.

              With the option -s, per-session logging is enabled.  Input from tcp_read is output to the file
              logfile.sess.  As the session is automatically discriminated by the filename, the contents are
              raw (no $TCP_PROMPT).  The option  -a applies as above.  Per-session logging  and  logging  of
              all data in one file are not mutually exclusive.

              The option -c closes all logging, both complete and per-session logs.

              The  options  -n  and  -N  respectively turn off or restore output of data read by tcp_read to
              standard output; hence `tcp_log -cn' turns off all output by tcp_read.

              The  function  is  purely  a  convenient  front  end  to  setting  the  parameters   $TCP_LOG,
              $TCP_LOG_SESS, $TCP_SILENT, which are described below.

       tcp_rename old new
              Rename session old to session new.  The old name becomes invalid.

       tcp_sess [ sess [ command  ... ] ]
              With  no  arguments,  list all the open sessions and associated file descriptors.  The current
              session is marked with a star.   For  use  in  functions,  direct  access  to  the  parameters
              $tcp_by_name, $tcp_by_fd and $TCP_SESS is probably more convenient; see below.

              With  a  sess  argument,  set  the  current  session  to sess.  This is equivalent to changing
              $TCP_SESS directly.

              With additional arguments, temporarily set the current session while executing the string com-mand command
              mand  ....  The first argument is re-evaluated so as to expand aliases etc., but the remaining
              arguments are passed through as the appear to tcp_sess.  The original session is restored when
              tcp_sess exits.


   Advanced I/O
       tcp_command send-options ... send-arguments ...
              This  is  a  convenient front-end to tcp_send.  All arguments are passed to tcp_send, then the
              function pauses waiting for data.  While data is arriving at least every $TCP_TIMEOUT (default
              0.3)  seconds, data is handled and printed out according to the current settings.  Status 0 is
              always returned.

              This is generally only useful for interactive use, to prevent the display becoming  fragmented
              by output returned from the connection.  Within a programme or function it is generally better
              to handle reading data by a more explicit method.

       tcp_expect [ -q ] [ -p var ] [ -t  to | -T TO]
           [ -a | -s sess ... | -l sess,... ] pattern ...
              Wait for input matching any of the given patterns from any of the specified  sessions.   Input
              is ignored until an input line matches one of the given patterns; at this point status zero is
              returned, the matching line is stored in $TCP_LINE, and the full set of lines read during  the
              call to tcp_expect is stored in the array $tcp_expect_lines.

              Sessions are specified in the same way as tcp_read: the default is to use the current session,
              otherwise the sessions specified by -a, -s, or -l are used.

              Each pattern is a standard zsh extended-globbing pattern; note that it needs to be  quoted  to
              avoid  it  being expanded immediately by filename generation.  It must match the full line, so
              to match a substring there must be a `*' at the start  and  end.   The  line  matched  against
              includes the $TCP_PROMPT added by tcp_read.  It is possible to include the globbing flags `#b'
              or `#m' in the patterns to make backreferences available in  the  parameters  $MATCH,  $match,
              etc., as described in the base zsh documentation on pattern matching.

              Unlike  tcp_read,  the  default  behaviour  of  tcp_expect  is to block indefinitely until the
              required input is found.  This can be modified by specifying a timeout with -t  or  -T;  these
              function  as  in tcp_read, specifying a per-read or overall timeout, respectively, in seconds,
              as an integer or floating-point number.  As tcp_read, the function returns status 2 if a time-out timeout
              out occurs.

              The  function  returns as soon as any one of the patterns given match.  If the caller needs to
              know which of the patterns matched, the option -p var can be used; on return, $var is  set  to
              the  number  of the pattern using ordinary zsh indexing, i.e. the first is 1, and so on.  Note
              the absence of a `$' in front of var.  To avoid  clashes,  the  parameter  cannot  begin  with
              `_expect'.

              The option -q is passed directly down to tcp_read.

              As  all input is done via tcp_read, all the usual rules about output of lines read apply.  One
              exception is that the parameter $tcp_lines will only reflect  the  line  actually  matched  by
              tcp_expect; use $tcp_expect_lines for the full set of lines read during the function call.

       tcp_proxy
              This  is  a  simple-minded  function to accept a TCP connection and execute a command with I/O
              redirected to the connection.  Extreme caution should be taken as there is no security whatso-ever whatsoever
              ever  and  this  can  leave  your computer open to the world.  Ideally, it should only be used
              behind a firewall.

              The first argument is a TCP port on which the function will listen.

              The remaining arguments give a command and its arguments to execute with standard input, stan-dard standard
              dard  output and standard error redirected to the file descriptor on which the TCP session has
              been accepted.  If no command is given, a new zsh is started.  This  gives  everyone  on  your
              network direct access to your account, which in many cases will be a bad thing.

              The  command  is run in the background, so tcp_proxy can then accept new connections.  It con-tinues continues
              tinues to accept new connections until interrupted.

       tcp_spam [-ertv] [ -a | -s  sess | -l sess,... ] cmd ...
              Execute `cmd ...' for each session in turn.  Note this executes the command and arguments;  it
              does not send the command line as data unless the -t (transmit) option is given.

              The sessions may be selected explicitly with the standard -a, -s or -l options, or may be cho-sen chosen
              sen implicitly.  If none of the three options is given the rules  are:  first,  if  the  array
              $tcp_spam_list  is  set,  this  is  taken  as the list of sessions, otherwise all sessions are
              taken.  Second, any sessions given in the array $tcp_no_spam_list are removed from the list of
              sessions.

              Normally,  any  sessions added by the `-a' flag or when all sessions are chosen implicitly are
              spammed in alphabetic order; sessions given by the $tcp_spam_list array or on the command line
              are spammed in the order given.  The -r flag reverses the order however it was arrived it.

              The  -v  flag specifies that a $TCP_PROMPT will be output before each session.  This is output
              after any modification to TCP_SESS by the user-defined tcp_on_spam function  described  below.
              (Obviously that function is able to generate its own output.)

              If the option -e is present, the line given as cmd ... is executed using eval, otherwise it is
              executed without any further processing.

       tcp_talk
              This is a fairly simple-minded attempt to force input to the line editor to go straight to the
              default TCP_SESSION.

              An escape string, $TCP_TALK_ESCAPE, default `:', is used to allow access to normal shell oper-ation. operation.
              ation.  If it is on its own at the start of the line, or followed only by whitespace, the line
              editor  returns  to  normal operation.  Otherwise, the string and any following whitespace are
              skipped and the remainder of the line executed as shell input without any change of  the  line
              editor's operating mode.

              The  current implementation is somewhat deficient in terms of use of the command history.  For
              this reason, many users will prefer to use some form of alternative approach for sending  data
              easily  to  the current session.  One simple approach is to alias some special character (such
              as `%') to `tcp_command --'.

       tcp_wait
              The sole argument is an integer or floating point number which gives  the  seconds  to  delay.
              The shell will do nothing for that period except wait for input on all TCP sessions by calling
              tcp_read -a.  This is similar to the interactive behaviour at the command prompt when zle han-dlers handlers
              dlers are installed.


   `One-shot' file transfer
       tcp_point port
       tcp_shoot host port
              This  pair  of  functions provide a simple way to transfer a file between two hosts within the
              shell.  Note, however, that bulk data transfer is currently done using cat.   tcp_point  reads
              any  data arriving at port and sends it to standard output; tcp_shoot connects to port on host
              and sends its standard input.  Any unused port may be used; the standard mechanism for picking
              a port is to think of a random four-digit number above 1024 until one works.

              To transfer a file from host woodcock to host springes, on springes:

                     tcp_point 8091 >output_file

              and on woodcock:

                     tcp_shoot springes 8091 <input_file

              As these two functions do not require tcp_open to set up a TCP connection first, they may need
              to be autoloaded separately.


TCP USER-DEFINED FUNCTIONS
       Certain functions, if defined by the user, will be called by the function system in certain contexts.
       This  facility  depends on the module zsh/parameter, which is usually available in interactive shells
       as the completion system depends on it.  None of the functions need be defined; they  simply  provide
       convenient hooks when necessary.

       Typically, these are called after the requested action has been taken, so that the various parameters
       will reflect the new state.

       tcp_on_alias alias fd
              When an alias is defined, this function will be called with two arguments:  the  name  of  the
              alias, and the file descriptor of the corresponding session.

       tcp_on_awol sess fd
              If  the  function  tcp_fd_handler  is handling input from the line editor and detects that the
              file descriptor is no longer reusable, by default it removes it from the list of file descrip-
              tors  handled  by this method and prints a message.  If the function tcp_on_awol is defined it
              is called immediately before this point.  It may return status 100, which indicates  that  the
              normal  handling  should still be performed; any other return status indicates that no further
              action should be taken and the tcp_fd_handler should return immediately with the given status.
              Typically the action of tcp_on_awol will be to close the session.

              The  variable  TCP_INVALIDATE_ZLE  will be a non-empty string if it is necessary to invalidate
              the line editor display using `zle -I' before printing output from the function.

              (`AWOL' is military jargon for `absent without leave' or some variation.  It has no pre-exist-ing pre-existing
              ing technical meaning known to the author.)

       tcp_on_close sess fd
              This  is  called  with the name of a session being closed and the file descriptor which corre-sponded corresponded
              sponded to that session.  Both will be invalid by the time the function is called.

       tcp_on_open sess fd
              This is called after a new session has been defined with the session name and file  descriptor
              as arguments.  If it returns a non-zero status, opening the session is assumed to fail and the
              session is closed again; however, tcp_open will continue to attempt to open any remaining ses-sions sessions
              sions given on the command line.

       tcp_on_rename oldsess fd newsess
              This  is  called  after  a session has been renamed with the three arguments old session name,
              file descriptor, new session name.

       tcp_on_spam sess command ...
              This is called once for each session spammed, just before a command is executed for a  session
              by  tcp_spam.  The arguments are the session name followed by the command list to be executed.
              If tcp_spam was called with the option -t, the first command will be tcp_send.

              This function is called after $TCP_SESS is set to reflect  the  session  to  be  spammed,  but
              before  any  use  of  it is made.  Hence it is possible to alter the value of $TCP_SESS within
              this function.  For example, the session arguments to tcp_spam could include extra information
              to be stripped off and processed in tcp_on_spam.

              If  the  function  sets  the  parameter $REPLY to `done', the command line is not executed; in
              addition, no prompt is printed for the -v option to tcp_spam.

       tcp_on_unalias alias fd
              This is called with the name of an alias and the corresponding session's file descriptor after
              an alias has been deleted.


TCP UTILITY FUNCTIONS
       The following functions are used by the TCP function system but will rarely if ever need to be called
       directly.

       tcp_fd_handler
              This is the function installed by tcp_open for handling input from within the line editor,  if
              that is required.  It is in the format documented for the builtin `zle -F' in zshzle(1) .

              While active, the function sets the parameter TCP_HANDLER_ACTIVE to 1.  This allows shell code
              called internally (for example, by setting tcp_on_read) to tell if is being  called  when  the
              shell is otherwise idle at the editor prompt.

       tcp_output [ -q ] -P prompt -F fd -S sess
              This  function  is  used  for both logging and handling output to standard output, from within
              tcp_read and (if $TCP_OUTPUT is set) tcp_send.

              The prompt to use is specified by -P; the default is the empty string.  It can contain:
              %c     Expands to 1 if the session is the current session, otherwise  0.   Used  with  ternary
                     expressions such as `%(c.-.+)' to output `+' for the current session and `-' otherwise.

              %f     Replaced by the session's file descriptor.

              %s     Replaced by the session name.

              %%     Replaced by a single `%'.

              The option -q suppresses output to standard output, but not to any log files which are config-ured. configured.
              ured.

              The  -S  and  -F options are used to pass in the session name and file descriptor for possible
              replacement in the prompt.


TCP USER PARAMETERS
       Parameters follow the usual convention that uppercase is used for scalars and integers, while  lower-case lowercase
       case is used for normal and associative array.  It is always safe for user code to read these parame-ters. parameters.
       ters.  Some parameters may also be set; these are noted explicitly.   Others  are  included  in  this
       group  as  they are set by the function system for the user's benefit, i.e. setting them is typically
       not useful but is benign.

       It is often also useful to make settable  parameters  local  to  a  function.   For  example,  `local
       TCP_SILENT=1'  specifies that data read during the function call will not be printed to standard out-put, output,
       put, regardless of the setting outside the function.  Likewise, `local TCP_SESS=sess' sets a  session
       for  the  duration  of a function, and `local TCP_PROMPT=' specifies that no prompt is used for input
       during the function.

       tcp_expect_lines
              Array.  The set of lines  read  during  the  last  call  to  tcp_expect,  including  the  last
              ($TCP_LINE).

       tcp_filter
              Array. May be set directly.  A set of extended globbing patterns which, if matched in tcp_out-put, tcp_output,
              put, will cause the line not to be printed to standard output.  The patterns should be defined
              as described for the arguments to tcp_expect.  Output of line to log files is not affected.

       TCP_HANDLER_ACTIVE
              Scalar.   Set to 1 within tcp_fd_handler to indicate to functions called recursively that they
              have been called during an editor session.  Otherwise unset.

       TCP_LINE
              The last line read by tcp_read, and hence also tcp_expect.

       TCP_LINE_FD
              The file descriptor from which $TCP_LINE was read.  ${tcp_by_fd[$TCP_LINE_FD]} will  give  the
              corresponding session name.

       tcp_lines
              Array. The set of lines read during the last call to tcp_read, including the last ($TCP_LINE).

       TCP_LOG
              May be set directly, although it is also controlled by tcp_log.  The name of a file  to  which
              output  from all sessions will be sent.  The output is proceeded by the usual $TCP_PROMPT.  If
              it is not an absolute path name, it will follow the user's current directory.

       TCP_LOG_SESS
              May be set directly, although it is also controlled by tcp_log.  The prefix for a set of files
              to   which   output  from  each  session  separately  will  be  sent;  the  full  filename  is
              ${TCP_LOG_SESS}.sess.  Output to each file is raw; no prompt is added.  If it is not an  abso-lute absolute
              lute path name, it will follow the user's current directory.

       tcp_no_spam_list
              Array.  May be set directly.  See tcp_spam for how this is used.

       TCP_OUTPUT
              May  be  set  directly.  If a non-empty string, any data sent to a session by tcp_send will be
              logged.  This parameter gives the prompt to be used in a file specified by $TCP_LOG but not in
              a  file generated from $TCP_LOG_SESS.  The prompt string has the same format as TCP_PROMPT and
              the same rules for its use apply.

       TCP_PROMPT
              May be set directly.  Used as the prefix for data read by tcp_read which is printed  to  stan-dard standard
              dard output or to the log file given by $TCP_LOG, if any.  Any `%s', `%f' or `%%' occurring in
              the string will be replaced by the name of the session, the session's underlying file descrip-tor, descriptor,
              tor,  or  a  single  `%', respectively.  The expression `%c' expands to 1 if the session being
              read is the current session, else 0; this is  most  useful  in  ternary  expressions  such  as
              `%(c.-.+)' which outputs `+' if the session is the current one, else `-'.

       TCP_READ_DEBUG
              May be set directly.  If this has non-zero length, tcp_read will give some limited diagnostics
              about data being read.

       TCP_SECONDS_START
              This value is created and initialised to zero by tcp_open.

              The functions tcp_read and tcp_expect use the shell's SECONDS parameter for their  own  timing
              purposes.   If  that parameter is not of floating point type on entry to one of the functions,
              it will create a local parameter SECONDS  which  is  floating  point  and  set  the  parameter
              TCP_SECONDS_START  to  the  previous  value of $SECONDS.  If the parameter is already floating
              point, it is used without a local copy being created and TCP_SECONDS_START is not set.  As the
              global  value  is  zero,  the  shell  elapsed time is guaranteed to be the sum of $SECONDS and
              $TCP_SECONDS_START.

              This can be avoided by setting SECONDS globally to a floating point value  using  `typeset  -F
              SECONDS';  then the TCP functions will never make a local copy and never set TCP_SECONDS_START
              to a non-zero value.

       TCP_SESS
              May be set directly.  The current session; must refer to one of the  sessions  established  by
              tcp_open.

       TCP_SILENT
              May  be  set directly, although it is also controlled by tcp_log.  If of non-zero length, data
              read by tcp_read will not be written to standard output, though may still be written to a  log
              file.

       tcp_spam_list
              Array.   May  be  set  directly.  See the description of the function tcp_spam for how this is
              used.

       TCP_TALK_ESCAPE
              May be set directly.  See the description of the function tcp_talk for how this is used.

       TCP_TIMEOUT
              May be set directly.  Currently this is only used by the function tcp_command, see above.


TCP USER-DEFINED PARAMETERS
       The following parameters are not set by the function system, but have a special effect if set by  the
       user.

       tcp_on_read
              This  should  be  an associative array; if it is not, the behaviour is undefined.  Each key is
              the name of a shell function or other command, and the corresponding value is a shell  pattern
              (using  EXTENDED_GLOB).   Every  line  read  from  a  TCP session directly or indirectly using
              tcp_read (which includes lines read by tcp_expect) is compared against the  pattern.   If  the
              line  matches, the command given in the key is called with two arguments: the name of the ses-sion session
              sion from which the line was read, and the line itself.

              If any function called to handle a line returns a non-zero status, the  line  is  not  output.
              Thus  a tcp_on_read handler containing only the instruction `return 1' can be used to suppress
              output of particular lines (see, however, tcp_filter  above).   However,  the  line  is  still
              stored in TCP_LINE and tcp_lines; this occurs after all tcp_on_read processing.


TCP UTILITY PARAMETERS
       These  parameters  are  controlled  by the function system; they may be read directly, but should not
       usually be set by user code.

       tcp_aliases
              Associative array.  The keys are the names of sessions established with tcp_open;  each  value
              is a space-separated list of aliases which refer to that session.

       tcp_by_fd
              Associative array.  The keys are session file descriptors; each value is the name of that ses-sion. session.
              sion.

       tcp_by_name
              Associative array.  The keys are the names of sessions; each  value  is  the  file  descriptor
              associated with that session.


TCP EXAMPLES
       Here is a trivial example using a remote calculator.

       TO  create  a  calculator  server  on port 7337 (see the dc manual page for quite how infuriating the
       underlying command is):

              tcp_proxy 7337 dc

       To connect to this from the same host with a session also named `dc':

              tcp_open localhost 7337 dc

       To send a command to the remote session and wait a short while for output (assuming dc is the current
       session):

              tcp_command 2 4 + p

       To close the session:

              tcp_close

       The  tcp_proxy  needs  to  be  killed to be stopped.  Note this will not usually kill any connections
       which have already been accepted, and also that the port is not immediately available for reuse.

       The following chunk of code puts a list of sessions into an xterm header, with  the  current  session
       followed by a star.

              print -n "\033]2;TCP:" ${(k)tcp_by_name:/$TCP_SESS/$TCP_SESS\*} "\a"


TCP BUGS
       The  function  tcp_read uses the shell's normal read builtin.  As this reads a complete line at once,
       data arriving without a terminating newline can cause the function to block indefinitely.

       Though the function suite works well for interactive use and for data arriving in small amounts,  the
       performance when large amounts of data are being exchanged is likely to be extremely poor.



zsh 5.0.2                                     December 21, 2012                                 ZSHTCPSYS(1)

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