(zsh.info.gz) TCP Functions
Info Catalog
(zsh.info.gz) TCP Function System
(zsh.info.gz) TCP Parameters
24.2 TCP User Functions
=======================
24.2.1 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 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 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 different 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 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 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 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 available
sessions will be read, stored in the parameter $TCP_LINE, and
displayed to 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 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.
24.2.2 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 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.
24.2.3 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 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 connection 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 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, 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 standard -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 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 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 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 handlers are installed.
24.2.4 '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.
24.3 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 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 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 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 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.
24.4 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 Zle Builtins .
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 configured.
The -S and -F options are used to pass in the session name and file
descriptor for possible replacement in the prompt.
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