zshtcpsys
(1)
Name
zshtcpsys - zsh tcp system
Synopsis
Please see following description for synopsis
Description
User Commands 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 zshmod-
ules(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 corre-
sponding advice for the zftp functions described in zshzftp-
sys(1) .
There are functions corresponding to the basic I/O opera-
tions 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 automatically shown at the
terminal. Other facilities available including logging,
filtering and configurable 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 alphanu-
merics or underscores, and certainly do include white-
space.
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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 initialisation
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 argument is a file
descriptor open for listening for connections. No
function front-end is provided 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 under-
lies this file descriptor. A regular file is likely to
be unusable; a FIFO (pipe) of some sort will work bet-
ter, but note that it is not a good idea for two dif-
ferent 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
waiting; 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 neces-
sary for executing complete sets of send and read
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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 ses-
sion 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 parame-
ters 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 session, 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 use-
ful), 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 available sessions will be read,
stored in the parameter $TCP_LINE, and displayed to
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standard output 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 timeout 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 operation differs
little from a `print -r' to the session's file descrip-
tor, 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
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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 sub-
set 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 exclu-
sive.
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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 set-
ting 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 asso-
ciated 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 command .... 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 argu-
ments 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 han-
dled 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
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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 pat-
tern; 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, specify-
ing 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 timeout
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 con-
nection and execute a command with I/O redirected to
the connection. Extreme caution should be taken as
there is no security whatsoever and this can leave your
computer open to the world. Ideally, it should only be
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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 argu-
ments to execute with standard input, standard 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 continues 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 stan-
dard -a, -s or -l options, or may be chosen 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 ses-
sions.
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 modifi-
cation 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 with-
out 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
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TCP_SESSION.
An escape string, $TCP_TALK_ESCAPE, default `:', is
used to allow access to normal shell operation. 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 ses-
sion. 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 num-
ber 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 handlers 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, how-
ever, 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.
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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 avail-
able 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 descriptors 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-existing 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 corresponded to that ses-
sion. 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; how-
ever, tcp_open will continue to attempt to open any
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remaining sessions 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 com-
mand 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 corre-
sponding 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_HAN-
DLER_ACTIVE to 1. This allows shell code called inter-
nally (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
$TCP_OUTPUT is set) tcp_send.
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The prompt to use is specified by -P; the default is
the empty string. It can contain:
%c Expands to 1 if the session is the current ses-
sion, otherwise 0. Used with ternary expressions
such as `%(c.-.+)' to output `+' for the current
session and `-' otherwise.
%f Replaced by the session's file descriptor.
%s Replaced by the session name.
%% Replaced by a single `%'.
The option -q suppresses output to standard output, but
not to any log files which are configured.
The -S and -F options are used to pass in the session
name and file descriptor for possible replacement in
the prompt.
TCP USER PARAMETERS
Parameters follow the usual convention that uppercase is
used for scalars and integers, while lowercase is used for
normal and associative array. It is always safe for user
code to read these parameters. Some parameters may also be
set; these are noted explicitly. Others are included in
this group as they are set by the function system for the
user's benefit, i.e. setting them is typically not useful
but is benign.
It is often also useful to make settable parameters local to
a function. For example, `local TCP_SILENT=1' specifies
that data read during the function call will not be printed
to standard output, regardless of the setting outside the
function. Likewise, `local TCP_SESS=sess' sets a session
for the duration of a function, and `local TCP_PROMPT='
specifies that no prompt is used for input during the func-
tion.
tcp_expect_lines
Array. The set of lines read during the last call to
tcp_expect, including the last ($TCP_LINE).
tcp_filter
Array. May be set directly. A set of extended globbing
patterns which, if matched in tcp_output, will cause
the line not to be printed to standard output. The
patterns should be defined as described for the argu-
ments to tcp_expect. Output of line to log files is
not affected.
TCP_HANDLER_ACTIVE
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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 absolute
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 speci-
fied 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 standard 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
descriptor, or a single `%', respectively. The expres-
sion `%c' expands to 1 if the session being read is the
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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 parame-
ter SECONDS which is floating point and set the parame-
ter TCP_SECONDS_START to the previous value of $SEC-
ONDS. If the parameter is already floating point, it
is used without a local copy being created and TCP_SEC-
ONDS_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 func-
tion 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.
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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 session 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-sepa-
rated list of aliases which refer to that session.
tcp_by_fd
Associative array. The keys are session file descrip-
tors; each value is the name of that session.
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 man-
ual page for quite how infuriating the underlying command
is):
tcp_proxy 7337 dc
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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 indef-
initely.
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.
ATTRIBUTES
See attributes(5) for descriptions of the following
attributes:
+---------------+------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+------------------+
|Availability | shell/zsh |
+---------------+------------------+
|Stability | Volatile |
+---------------+------------------+
NOTES
This software was built from source available at
https://java.net/projects/solaris-userland. The original
community source was downloaded from
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http://downloads.source-
forge.net/project/zsh/zsh/5.0.5/zsh-5.0.5.tar.bz2
Further information about this software can be found on the
open source community website at http://www.zsh.org/.
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