tack - terminfo action checker


       tack [-itV] [term]


       The  tack  program has three purposes: (1) to help you build a new ter-
       minfo entry describing an unknown terminal, (2) to test the correctness
       of an existing entry, and (3) to develop the correct pad timings needed
       to ensure that screen updates do not  fall  behind  the  incoming  data

       Tack presents a series of screen-painting and interactive tests in ways
       which are intended to make any mismatches between  the  terminfo  entry
       and  reality  visually obvious.  Tack also provides tools that can help
       in understanding how the terminal operates.


       -i     Usually tack will send the reset and init strings to the  termi-
              nal  when the program starts up.  The -i option will inhibit the
              terminal initialization.

       -t     Tell tack to override the terminfo settings for  basic  terminal
              functions.   When this option is set tack will translate (cr) to
              \r, (cud1) to \n, (ind) to \n, (nel)  to  \r\n,  (cub1)  to  \b,
              (bel) to \007, (ff) to \f and (ht) to \t.

       -V     Display the version information and exit.

       term   Terminfo  terminal  name  to be tested.  If not present then the
              $TERM environment variable will be used.


       Since tack is designed to test terminfo entries it is not  possible  to
       rely on the correctness of the terminfo data base.  Because of this the
       menuing system used with tack  is  vary  primitive.   When  a  menu  is
       printed  it will scroll the entire screen.  To compensate for this ver-
       bose menu system tack  permits  menu  selection  type  ahead.   If  you
       already  know  what  action you would like tack to perform then you can
       enter that value immediately and avoid the menu display.  When in doubt
       the  question  mark (?) is a good character to type.  A carriage return
       will execute the default action.  These default actions are designed to
       run all the standard tests.

       When  tack  first comes up it will display some basic information about
       the terminal.  Take some time to verify this  information.   If  it  is
       wrong  many of the subsequent tests will fail.  The most important item
       is the screen size.  If the screen size is wrong there is no  point  in
       proceeding.   (home)  and  (clear)  are also critical to the success of
       subsequent tests.  The values of (cr) (ind) (cub1) and (ht) may  effect
       the  tests if they are defined incorrectly.  If they are undefined tack
       will set them to reasonable defaults.  The last two entries on the dis-
       play  are the enquire and acknowledge strings.  These strings are taken
       from the user strings (u9) and (u8).

       By now you must be wondering why the terminfo  names  are  enclosed  in
       parenthesis.   This  has  no  profound meaning other than it makes them
       stand out.  The tack program uses this convention any time it  displays
       a terminfo name.  Remember tack is designed to rely on as little of the
       terminfo entry as possible.


       Tack has a number of tools that are designed to help gather information
       about the terminal.  Although these functions are not dependent on ter-
       minal type, you may wish to execute tack with options -it.   This  will
       turn off initialization and default the standard entries.

       These  tools may be reached from the main menu by selecting the "tools"

       Echo tool:  All data typed from the keyboard will be echoed back to the
       terminal.  Control characters are not translated to the up arrow format
       but are sent as control characters.  This allows you to test an  escape
       sequence  and  see what it actually does.  You may also elect to enable
       hex output on echo tool this will echo the characters  in  hexadecimal.
       Once  the  test  is running you may enter the "lines" or "columns" key-
       words which will display a pattern that will help  you  determine  your
       screen  size.   A  complete list of keywords will be displayed when the
       test starts.  Type "help" to redisplay the list of available commands.

       Reply tool:  This tool acts much like the echo tool, but control  char-
       acters  that are sent from the terminal more than one character after a
       carriage return will be expanded to the up arrow format.   For  example
       on a standard ANSI terminal you may type:

                 CR ESC [ c

       and the response will be echoed as something like:

                 ^[ [ ? 6 c

       ANSI  sgr  display:   This  test assumes you have an ANSI terminal.  It
       goes through attribute numbers 0 to 79, displaying  each  in  turn  and
       using  that  SGR number to write the text.  This shows you which of the
       SGR modes are actually implemented by the terminal.  Note: some  termi-
       nals  (such  as Tektronix color) use the private use characters to aug-
       ment the functionality of the SGR command.  These private  use  charac-
       ters  may be interjected into the escape sequence by typing the charac-
       ter ( <, =, >, ? ) after the original display has been shown.

       ANSI status reports:   This  test  queries  the  terminal  in  standard
       ANSI/VT-100  fashion.  The results of this test may help determine what
       options are supported by your terminal.

       ANSI character sets:  This test displays the character  sets  available
       on  a ANSI/VT-100 style terminal.  Character sets on a real VT-100 ter-
       minal are usually defined with smacs=\E(0 and  rmacs=\E(B.   The  first
       character after the escape defines the font bank.  The second character
       defines the character set.  This test allows you to  view  any  of  the
       possible  combinations.   Private use character sets are defined by the
       digits.  Standard character sets are located in the alphabetic range.


       You can verify the correctness of an entry  with  the  "begin  testing"
       function.   This  entry is the default action and will be chosen if you
       hit carriage return (or enter).  This will bring up  a  secondary  menu
       that allows you to select more specific tests.

       The  general philosophy of the program is, for each capability, to send
       an appropriate test pattern to the terminal then send a description  of
       what  the user should expect.  Occasionally (as when checking function-
       key capabilities) the program will ask you to enter  input  for  it  to

       If  the test fails then you have the option of dynamically changing the
       terminfo entry and re-running the test.  This is done  with  the  "edit
       terminfo" menu item.  The edit submenu allows you to change the offend-
       ing terminfo entry and immediately retest  the  capability.   The  edit
       menu  lets  you do other things with the terminfo, such as; display the
       entire terminfo entry, display which caps have been tested and  display
       which  caps  cannot  be tested.  This menu also allows you to write the
       newly modified terminfo to disc.  If you have made any modifications to
       the  terminfo  tack  will  ask you if you want to save the file to disc
       before it exits.  The filename will be the same as the  terminal  name.
       After  the  program  exits  you can run the tic(1M) compiler on the new
       terminfo to install it in the terminfo data base.


Theory of Overruns and Padding

       Some terminals require significant amounts of time (that is, more  than
       one  transmitted-character  interval)  to do screen updates that change
       large portions of the screen, such as screen clears,  line  insertions,
       line  deletions, and scrolls (including scrolls triggered by line feeds
       or a write to the lowest, right-hand-most cell of the screen).

       If the computer continues to send characters to the terminal while  one
       of  these time-consuming operations is going on, the screen may be gar-
       bled.  Since  the  length  of  a  character  transmission  time  varies
       inversely  with  transmission  speed  in cps, entries which function at
       lower speeds may break at higher speeds.

       Similar problems result if the host machine is simply  sending  charac-
       ters  at  a  sustained  rate  faster  than  the terminal can buffer and
       process them.  In either case, when the terminal  cannot  process  them
       and  cannot  tell the host to stop soon enough, it will just drop them.
       The dropped characters could be text, escape sequences  or  the  escape
       character  itself,  causing some really strange-looking displays.  This
       kind of glitch is called an overrun.

       In terminfo entries, you can attach a pad time to each string  capabil-
       ity  that  is a number of milliseconds to delay after sending it.  This
       will give the terminal time to catch up and avoid overruns.

       If you are running a software terminal emulator, or you  are  on  an  X
       pseudo-tty, or your terminal is on an RS-232C line which correctly han-
       dles RTS/CTS hardware flow control, then pads are not  strictly  neces-
       sary.  However, some display packages (such as ncurses(3X)) use the pad
       counts to calculate the fastest way  to  implement  certain  functions.
       For  example:  scrolling the screen may be faster than deleting the top

       One common way to avoid overruns is  with  XON/XOFF  handshaking.   But
       even  this  handshake  may have problems at high baud rates.  This is a
       result of the way XON/XOFF works.  The terminal tells the host to  stop
       with  an  XOFF.   When  the host gets this character, it stops sending.
       However, there is a small amount of time between the stop  request  and
       the  actual  stop.   During  this window, the terminal must continue to
       accept characters even though it has told the host  to  stop.   If  the
       terminal sends the stop request too late, then its internal buffer will
       overflow.  If it sends the stop character too early, then the  terminal
       is  not getting the most efficient use out of its internal buffers.  In
       a real application at high baud rates, a terminal could get a dozen  or
       more characters before the host gets around to suspending transmission.
       Connecting the terminal over a  network  will  make  the  problem  much

       (RTS/CTS  handshaking  does not have this problem because the UARTs are
       signal-connected and the "stop flow" is done at the lowest level, with-
       out software intervention).

Timing your terminal

       In  order to get accurate timings from your terminal tack needs to know
       when the terminal has finished processing all the characters that  were
       sent.   This requires a different type of handshaking than the XON/XOFF
       that is supported by most terminals.  Tack needs to send a  request  to
       the  terminal and wait for its reply.  Many terminals will respond with
       an ACK when they receive an ENQ.  This is the  preferred  method  since
       the  sequence  is  short.   ANSI/VT-100  style terminals can mimic this
       handshake with  the  escape  sequence  that  requests  "primary  device

          ESC [ c

       The terminal will respond with a sequence like:

          ESC [ ? 1 ; 0 c

       Tack  assumes  that  (u9)  is the enquire sequence and that (u8) is the
       acknowledge string.  A VT-100 style  terminal  could  set  u9=\E[c  and
       u8=\E[?1;0c.  Acknowledge strings fall into two categories.  1) Strings
       with a unique terminating character and, 2) strings  of  fixed  length.
       The  acknowledge  string  for  the VT-100 is of the first type since it
       always ends with the letter "c".  Some Tektronics terminals have  fixed
       length  acknowledge  strings.   Tack  supports both types of strings by
       scanning for the terminating character until the length of the expected
       acknowledge  string  has  arrived.   (u8) should be set to some typical
       acknowledge that will be returned when (u9) is sent.

       Tack will test this sequence before running any of the pad tests or the
       function key tests.  Tack will ask you the following:

           Hit lower case g to start testing...

       After  it  sends this message it will send the enquire string.  It will
       then read characters from the terminal until it sees the letter g.

Testing and Repairing Pad Timings

       The pad timings in distributed terminfo entries  are  often  incorrect.
       One  major motivation for this program is to make it relatively easy to
       tune these timings.

       You can verify and edit the pad timings for a terminal with  the  "test
       string  capabilities"  function  (this is also part of the "normal test
       sequence" function).

       The key to determining pad times is to find out the effective baud rate
       of  the  terminal.   The  effective  baud rate determines the number of
       characters per second that the terminal can accept without either hand-
       shaking  or losing data.  This rate is frequently less than the nominal
       cps rate on the RS-232 line.

       Tack uses the effective baud rate to judge the duration of the test and
       how much a particular escape sequence will perturb the terminal.

       Each  pad test has two associated variables that can be tweaked to help
       verify the correctness of the pad timings.  One is the pad test length.
       The  other  is  the  pad  multiplier,  which  is used if the pad prefix
       includes "*".  In curses use, it is often the first  parameter  of  the
       capability (if there is one).  For a capability like (dch) or (il) this
       will be the number of character positions or  lines  affected,  respec-

       Tack  will  run  the pad tests and display the results to the terminal.
       On capabilities that have multipliers tack will not tell you if the pad
       needs  the  multiplier or not.  You must make this decision yourself by
       rerunning the test with a different multiplier.  If the padding changes
       in  proportion  to  the multiplier than the multiplier is required.  If
       the multiplier has little or no effect on the  suggested  padding  then
       the multiplier is not needed.  Some capabilities will take several runs
       to get a good feel for the correct values.  You may wish  to  make  the
       test longer to get more accurate results.  System load will also effect
       the results (a heavily loaded system will not stress  the  terminal  as
       much, possibly leading to pad timings that are too short).


       The  tests  done at the beginning of the program are assumed to be cor-
       rect later in the code.  In particular, tack  displays  the  number  of
       lines  and  columns indicated in the terminfo entry as part of its ini-
       tial output.  If these values are wrong a large number  of  tests  will
       fail or give incorrect results.


       tack.log    If  logging  is  enabled then all characters written to the
                   terminal will also be written to the log file.  This  gives
                   you  the ability to see how the tests were performed.  This
                   feature is disabled by default.

       term        If you make changes to the terminfo entry  tack  will  save
                   the  new  terminfo  to a file.  The file will have the same
                   name as the terminal name.


       terminfo(5), ncurses(3X), tic(1M), infocmp(1M).  You should  also  have
       the documentation supplied by the terminal manufacturer.


       If the screen size is incorrect, many of the tests will fail.


       Concept,   design,   and   original  implementation  by  Daniel  Weaver
       <>.  Portions of the code and documentation  are  by
       Eric S. Raymond <>.