autoexpect



AUTOEXPECT(1)                                                    AUTOEXPECT(1)




NAME

       autoexpect - generate an Expect script from watching a session


SYNOPSIS

       autoexpect [ args ] [ program args...  ]


INTRODUCTION

       autoexpect  watches you interacting with another program and creates an
       Expect script that  reproduces  your  interactions.   For  straightline
       scripts,  autoexpect  saves  substantial  time  over writing scripts by
       hand.  Even if you are an Expect expert, you will find it convenient to
       use autoexpect to automate the more mindless parts of interactions.  It
       is much easier to cut/paste hunks of autoexpect scripts  together  than
       to write them from scratch.  And if you are a beginner, you may be able
       to get away with learning nothing more about Expect than  how  to  call
       autoexpect.

       The  simplest way to use autoexpect is to call it from the command line
       with no arguments.  For example:

            % autoexpect

       By default, autoexpect spawns a shell for you.  Given  a  program  name
       and arguments, autoexpect spawns that program.  For example:

            % autoexpect ftp ftp.cme.nist.gov

       Once your spawned program is running, interact normally.  When you have
       exited the shell (or program that you specified), autoexpect will  cre-
       ate a new script for you.  By default, autoexpect writes the new script
       to "script.exp".  You can override this with the -f flag followed by  a
       new script name.

       The  following  example  runs  "ftp  ftp.cme.nist.gov"  and  stores the
       resulting Expect script in the file "nist".

            % autoexpect -f nist ftp ftp.cme.nist.gov

       It is important to understand that  autoexpect  does  not  guarantee  a
       working script because it necessarily has to guess about certain things
       - and occasionally it guesses wrong.  However, it is usually very  easy
       to identify and fix these problems.  The typical problems are:

              ·   Timing.   A  surprisingly large number of programs (rn, ksh,
                  zsh,  telnet,  etc.)  and  devices  (e.g.,  modems)   ignore
                  keystrokes  that arrive "too quickly" after prompts.  If you
                  find your new script hanging up at one spot,  try  adding  a
                  short sleep just before the previous send.

                  You  can  force  this  behavior throughout by overriding the
                  variable "force_conservative" near the beginning of the gen-
                  erated  script.   This  "conservative" mode makes autoexpect
                  automatically pause briefly (one tenth of a  second)  before
                  sending  each character.  This pacifies every program I know
                  of.

                  This conservative mode is useful if you just want to quickly
                  reassure  yourself  that  the problem is a timing one (or if
                  you really don’t care about how fast the script runs).  This
                  same  mode  can  be forced before script generation by using
                  the -c flag.

                  Fortunately, these timing spots are rare.  For example, tel-
                  net  ignores  characters  only  after  entering  its  escape
                  sequence.  Modems only ignore characters  immediately  after
                  connecting  to  them  for  the  first  time.  A few programs
                  exhibit this behavior all the  time  but  typically  have  a
                  switch  to  disable  it.  For example, rn’s -T flag disables
                  this behavior.

                  The following  example  starts  autoexpect  in  conservative
                  mode.

                       autoexpect -c

                  The  -C flag defines a key to toggle conservative mode.  The
                  following example  starts  autoexpect  (in  non-conservative
                  mode)  with  ^L as the toggle.  (Note that the ^L is entered
                  literally - i.e., enter a real control-L).

                       autoexpect -C ^L

                  The following example starts autoexpect in conservative mode
                  with ^L as the toggle.

                       autoexpect -c -C ^L


              ·   Echoing.  Many program echo characters.  For example, if you
                  type "more" to a shell, what autoexpect actually sees is:

                       you typed ’m’,
                       computer typed ’m’,
                       you typed ’o’,
                       computer typed ’o’,
                       you typed ’r’,
                       computer typed ’r’,
                       ...

                  Without specific knowledge of the program, it is  impossible
                  to  know  if  you  are  waiting to see each character echoed
                  before typing the next.  If autoexpect sees characters being
                  echoed,  it  assumes  that  it  can send them all as a group
                  rather  than  interleaving  them  the  way  they  originally
                  appeared.   This  makes  the  script  more pleasant to read.
                  However, it could conceivably be incorrect if you really had
                  to wait to see each character echoed.


              ·   Change.   Autoexpect records every character from the inter-
                  action in the script.  This is desirable  because  it  gives
                  you  the  ability to make judgements about what is important
                  and what can be replaced with a pattern match.

                  On the other hand, if you use commands whose output  differs
                  from  run  to run, the generated scripts are not going to be
                  correct.  For example, the "date"  command  always  produces
                  different  output.   So using the date command while running
                  autoexpect is a sure way  to  produce  a  script  that  will
                  require editing in order for it to work.

                  The  -p  flag  puts  autoexpect into "prompt mode".  In this
                  mode, autoexpect will only look for the  the  last  line  of
                  program  output - which is usually the prompt.  This handles
                  the date problem (see above) and most others.

                  The following example starts autoexpect in prompt mode.

                       autoexpect -p

                  The -P flag defines a key to toggle prompt mode.   The  fol-
                  lowing  example  starts autoexpect (in non-prompt mode) with
                  ^P as the toggle.  Note that the ^P is entered  literally  -
                  i.e., enter a real control-P.

                       autoexpect -P ^P

                  The  following example starts autoexpect in prompt mode with
                  ^P as the toggle.

                       autoexpect -p -P ^P



OTHER FLAGS

       The -quiet flag disables informational messages produced by autoexpect.

       The  -Q flag names a quote character which can be used to enter charac-
       ters that autoexpect would otherwise consume because they are  used  as
       toggles.

       The  following  example shows a number of flags with quote used to pro-
       vide a way of entering the toggles literally.

            autoexpect -P ^P -C ^L -Q ^Q



STYLE

       I don’t know if there is a "style" for Expect programs  but  autoexpect
       should  definitely  not be held up as any model of style.  For example,
       autoexpect uses features of Expect that are intended  specifically  for
       computer-generated scripting.  So don’t try to faithfully write scripts
       that appear as if they were generated by autoexpect.  This is not  use-
       ful.

       On  the  other hand, autoexpect scripts do show some worthwhile things.
       For example, you can see how any string must be quoted in order to  use
       it in a Tcl script simply by running the strings through autoexpect.



SEE ALSO

       "Exploring  Expect: A Tcl-Based Toolkit for Automating Interactive Pro-
       grams" by Don Libes, O’Reilly and Associates, January 1995.


AUTHOR

       Don Libes, National Institute of Standards and Technology

       expect and autoexpect are in the  public  domain.   NIST  and  I  would
       appreciate credit if these programs or parts of them are used.




                                 30 June 1995                    AUTOEXPECT(1)

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