autoexpect

AUTOEXPECT(1)               General Commands Manual              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
       create 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
                  generated 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,
                  telnet 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
                  interaction 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
                  following 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
       characters that autoexpect would otherwise consume because they are
       used as toggles.

       The following example shows a number of flags with quote used to
       provide 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
       useful.

       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
       Programs" 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)