24.5 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 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_output, 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 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 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 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 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 ‘-’.

If the prompt starts with %P, this is stripped and the complete result of the previous stage is passed through standard prompt %-style formatting before being output.

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.

24.6 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.

24.7 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 session.

tcp_by_name

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