# man > zshtcpsys(1) [_ZSHTCPSYS_(1)](https://www.chedong.com/phpMan.php/man/ZSHTCPSYS/1/markdown) General Commands Manual [_ZSHTCPSYS_(1)](https://www.chedong.com/phpMan.php/man/ZSHTCPSYS/1/markdown) ## 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)](https://www.chedong.com/phpMan.php/man/zshmodules/1/markdown). 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 [_zshzftpsys_(1)](https://www.chedong.com/phpMan.php/man/zshzftpsys/1/markdown). 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 ses‐ sions 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 log‐ ging, 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 ses‐ sion is attached). It is recommended that session names not include `funny' charac‐ ters, where funny characters are not well-defined but certainly do not include al‐ phanumerics 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 direc‐ tory 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 listen‐ ing 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 ses‐ sion is created in the usual way and is largely indistinguishable from an active con‐ nection 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 infor‐ mational 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 inter‐ active, **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 **$TCP_SESS**; see below for more detail about the parameters used by the system. The function **tcp_on_open**, if defined, is called when a session is opened. See the de‐ scription below. **tcp_close **[ **-qn **] [ **-a **| **-l _**sess_[**,**...] | _sess_ ... ] Close the named sessions, or the current session if none is given, or all open ses‐ sions if **-a **is given. The options **-l **and **-s **are both handled for consistency with **tcp_open**, although the latter is redundant. If the session being closed is the current one, **$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 **op‐ tion 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 **$TCP_PROMPT **will be shown at the start of the line; the default form for this includes the name of the session being read. See be‐ low for more information on these parameters. In this mode, **tcp_read **can be called repeatedly until it returns status 2 which indicates all pending input from all speci‐ fied sessions has been handled. With the option **-b**, equivalent to an infinite timeout, the function will block until a line is available to read from one of the specified sessions. However, only a single line is returned. The option **-d **indicates that all pending input should be drained. In this case **tcp_read **may process multiple lines in the manner given above; only the last is stored in **$TCP_LINE**, but the complete set is stored in the array **$tcp_lines**. This is cleared at the start of each call to **tcp_read**. The options **-t **and **-T **specify a timeout in seconds, which may be a floating point num‐ ber for increased accuracy. With **-t **the timeout is applied before each line read. With **-T**, the timeout applies to the overall operation, possibly including multiple read operations if the option **-d **is present; without this option, there is no distinc‐ tion between **-t **and **-T**. The function does not print informational messages, but if the option **-q **is given, no error message is printed for a non-existent session. A return status of 2 indicates a timeout or no data to read. Any other non-zero re‐ turn status indicates some error condition. See **tcp_log **for how to control where data is sent by **tcp_read**. **tcp_send **[ **-cnq **] [ **-s _**sess_ | **-l _**sess_[**,**...] ] _data_ ... **tcp_send **[ **-cnq **] **-a _**data_ ... Send the supplied data strings to all the specified sessions in turn. The underlying operation differs little from a `**print -r**' to the session's file descriptor, although it attempts to prevent the shell from dying owing to a **SIGPIPE **caused by an attempt to write to a defunct session. The option **-c **causes **tcp_send **to behave like **cat**. It reads lines from standard input until end of input and sends them in turn to the specified session(s) exactly as if they were given as _data_ arguments to individual **tcp_send **commands. The option **-n **prevents **tcp_send **from putting a newline at the end of the data strings. The remaining options all behave as for **tcp_read**. The data arguments are not further processed once they have been passed to **tcp_send**; they are simply passed down to **print -r**. If the parameter **$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**. ### 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 af‐ fected. 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_ [ _arg_ ... ] ] ] 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 pa‐ rameters **$tcp_by_name**, **$tcp_by_fd **and **$TCP_SESS **is probably more convenient; see be‐ low. With a _sess_ argument, set the current session to _sess_. This is equivalent to changing **$TCP_SESS **directly. With additional arguments, temporarily set the current session while executing `_com‐_ _mand_ _arg_ ...'. _command_ is re-evaluated so as to expand aliases etc., but the remain‐ ing _arg_s are passed through as that appear to **tcp_sess**. The original session is re‐ stored when **tcp_sess **exits. ### Advanced I/O **tcp_command _**send-option_ ... _send-argument_ ... 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 **$TCP_TIMEOUT **(default 0.3) seconds, data is handled and printed out according to the current settings. Status 0 is always returned. This is generally only useful for interactive use, to prevent the display becoming fragmented by output returned from the connection. Within a programme or function it is generally better to handle reading data by a more explicit method. **tcp_expect **[ **-q **] [ **-p _**var_ | **-P _**var_ ] [ **-t _**TO_ | **-T _**TO_ ] [ **-a **| **-s _**sess_ | **-l _**sess_[**,**...] ] _pattern_ ... Wait for input matching any of the given _pattern_s from any of the specified sessions. Input is ignored until an input line matches one of the given patterns; at this point status zero is returned, the matching line is stored in **$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 avail‐ able in the parameters **$MATCH**, **$match**, etc., as described in the base zsh documenta‐ tion 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, respec‐ tively, 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 index -1 is used if there is a timeout and 0 if there is no match. The option **-P _**var_ works similarly to **-p**, but instead of numerical indexes the regular arguments must begin with a prefix followed by a colon: that prefix is then used as a tag to which _var_ is set when the argument matches. The tag **timeout **is used if there is a timeout and the empty string if there is no match. Note it is acceptable for different arguments to start with the same prefix if the matches do not need to be distinguished. 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 ap‐ ply. One exception is that the parameter **$tcp_lines **will only reflect the line actu‐ ally matched by **tcp_expect**; use **$tcp_expect_lines **for the full set of lines read dur‐ ing 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 se‐ curity 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 in‐ put, 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_ [ _arg_ ... ] Execute `_cmd_ [ _arg_ ... ]' 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) op‐ tion 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 re‐ moved from the list of sessions. Normally, any sessions added by the `**-a**' flag or when all sessions are chosen implic‐ itly are spammed in alphabetic order; sessions given by the **$tcp_spam_list **array or on the command line are spammed in the order given. The **-r **flag reverses the order how‐ ever it was arrived it. The **-v **flag specifies that a **$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 de‐ scribed below. (Obviously that function is able to generate its own output.) If the option **-e **is present, the line given as `_cmd_ [ _arg_ ... ]' 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_SESS**. 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 his‐ tory. For this reason, many users will prefer to use some form of alternative ap‐ proach 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. ### `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