| 1 | .TH AUTOEXPECT 1 "30 June 1995" |
| 2 | .SH NAME |
| 3 | autoexpect \- generate an Expect script from watching a session |
| 4 | .SH SYNOPSIS |
| 5 | .B autoexpect |
| 6 | [ |
| 7 | .I args |
| 8 | ] |
| 9 | [ |
| 10 | .I program args... |
| 11 | ] |
| 12 | .br |
| 13 | .SH INTRODUCTION |
| 14 | |
| 15 | autoexpect watches you interacting with another program and creates an |
| 16 | Expect script that reproduces your interactions. For straightline |
| 17 | scripts, autoexpect saves substantial time over writing scripts by |
| 18 | hand. Even if you are an Expect expert, you will find it convenient |
| 19 | to use autoexpect to automate the more mindless parts of interactions. |
| 20 | It is much easier to cut/paste hunks of autoexpect scripts together |
| 21 | than to write them from scratch. And if you are a beginner, you may |
| 22 | be able to get away with learning nothing more about Expect than how |
| 23 | to call autoexpect. |
| 24 | |
| 25 | The simplest way to use autoexpect is to call it from the command line |
| 26 | with no arguments. For example: |
| 27 | |
| 28 | % autoexpect |
| 29 | |
| 30 | By default, autoexpect spawns a shell for you. Given a program name |
| 31 | and arguments, autoexpect spawns that program. For example: |
| 32 | |
| 33 | % autoexpect ftp ftp.cme.nist.gov |
| 34 | |
| 35 | Once your spawned program is running, interact normally. When you |
| 36 | have exited the shell (or program that you specified), autoexpect will |
| 37 | create a new script for you. By default, autoexpect writes the new |
| 38 | script to "script.exp". You can override this with the \-f flag |
| 39 | followed by a new script name. |
| 40 | |
| 41 | The following example runs "ftp ftp.cme.nist.gov" and stores the |
| 42 | resulting Expect script in the file "nist". |
| 43 | .nf |
| 44 | |
| 45 | % autoexpect \-f nist ftp ftp.cme.nist.gov |
| 46 | |
| 47 | .fi |
| 48 | It is important to understand that |
| 49 | autoexpect does not guarantee a working script because it necessarily |
| 50 | has to guess about certain things \- and occasionally it guesses wrong. |
| 51 | However, it is usually very easy to identify and fix these problems. |
| 52 | The typical problems are: |
| 53 | .RS |
| 54 | .TP 4 |
| 55 | \(bu |
| 56 | Timing. A surprisingly large number of programs (rn, ksh, zsh, |
| 57 | telnet, etc.) and devices (e.g., modems) ignore keystrokes that arrive |
| 58 | "too quickly" after prompts. If you find your new script hanging up |
| 59 | at one spot, try adding a short sleep just before the previous send. |
| 60 | |
| 61 | You can force this behavior throughout by overriding the variable |
| 62 | "force_conservative" near the beginning of the generated script. This |
| 63 | "conservative" mode makes autoexpect automatically pause briefly (one |
| 64 | tenth of a second) before sending each character. This pacifies every |
| 65 | program I know of. |
| 66 | |
| 67 | This conservative mode is useful if you just want to quickly reassure |
| 68 | yourself that the problem is a timing one (or if you really don't care |
| 69 | about how fast the script runs). This same mode can be forced before |
| 70 | script generation by using the \-c flag. |
| 71 | |
| 72 | Fortunately, these timing spots are rare. For example, telnet ignores |
| 73 | characters only after entering its escape sequence. Modems only |
| 74 | ignore characters immediately after connecting to them for the first |
| 75 | time. A few programs exhibit this behavior all the time but typically |
| 76 | have a switch to disable it. For example, rn's \-T flag disables this |
| 77 | behavior. |
| 78 | |
| 79 | The following example starts autoexpect in conservative |
| 80 | mode. |
| 81 | .nf |
| 82 | |
| 83 | autoexpect \-c |
| 84 | |
| 85 | .fi |
| 86 | The \-C flag defines a key to toggle conservative mode. |
| 87 | The following example starts autoexpect (in non-conservative |
| 88 | mode) with ^L as the toggle. (Note that the ^L is |
| 89 | entered literally - i.e., enter a real control-L). |
| 90 | .nf |
| 91 | |
| 92 | autoexpect \-C ^L |
| 93 | |
| 94 | .fi |
| 95 | The following example starts autoexpect in conservative |
| 96 | mode with ^L as the toggle. |
| 97 | .nf |
| 98 | |
| 99 | autoexpect \-c \-C ^L |
| 100 | |
| 101 | .fi |
| 102 | .TP |
| 103 | \(bu |
| 104 | Echoing. Many program echo characters. For example, if you type |
| 105 | "more" to a shell, what autoexpect actually sees is: |
| 106 | .nf |
| 107 | |
| 108 | you typed 'm', |
| 109 | computer typed 'm', |
| 110 | you typed 'o', |
| 111 | computer typed 'o', |
| 112 | you typed 'r', |
| 113 | computer typed 'r', |
| 114 | ... |
| 115 | .fi |
| 116 | |
| 117 | Without specific knowledge of the program, it is impossible to know if |
| 118 | you are waiting to see each character echoed before typing the next. |
| 119 | If autoexpect sees characters being echoed, it assumes that it can |
| 120 | send them all as a group rather than interleaving them the way they |
| 121 | originally appeared. This makes the script more pleasant to read. |
| 122 | However, it could conceivably be incorrect if you really had to wait |
| 123 | to see each character echoed. |
| 124 | |
| 125 | .TP |
| 126 | \(bu |
| 127 | Change. Autoexpect records every character from the interaction in |
| 128 | the script. This is desirable because it gives you the ability to |
| 129 | make judgements about what is important and what can be replaced with |
| 130 | a pattern match. |
| 131 | |
| 132 | On the other hand, if you use commands whose output differs from run |
| 133 | to run, the generated scripts are not going to be correct. For |
| 134 | example, the "date" command always produces different output. So |
| 135 | using the date command while running autoexpect is a sure way to |
| 136 | produce a script that will require editing in order for it to work. |
| 137 | |
| 138 | The \-p flag puts autoexpect into "prompt mode". In this mode, |
| 139 | autoexpect will only look for the the last line of program output \- |
| 140 | which is usually the prompt. This handles the date problem (see |
| 141 | above) and most others. |
| 142 | |
| 143 | The following example starts autoexpect in prompt mode. |
| 144 | .nf |
| 145 | |
| 146 | autoexpect \-p |
| 147 | |
| 148 | .fi |
| 149 | The \-P flag defines a key to toggle prompt mode. The following |
| 150 | example starts autoexpect (in non-prompt mode) with ^P as the toggle. |
| 151 | Note that the ^P is entered literally - i.e., enter a real control-P. |
| 152 | .nf |
| 153 | |
| 154 | autoexpect \-P ^P |
| 155 | |
| 156 | .fi |
| 157 | The following example starts autoexpect in prompt mode with ^P as the toggle. |
| 158 | .nf |
| 159 | |
| 160 | autoexpect \-p \-P ^P |
| 161 | |
| 162 | .fi |
| 163 | .SH OTHER FLAGS |
| 164 | The |
| 165 | .B \-quiet |
| 166 | flag disables informational messages produced by autoexpect. |
| 167 | |
| 168 | The |
| 169 | .B \-Q |
| 170 | flag names a quote character which can be used to enter characters |
| 171 | that autoexpect would otherwise consume because they are used as toggles. |
| 172 | |
| 173 | The following example shows a number of flags with quote used to |
| 174 | provide a way of entering the toggles literally. |
| 175 | .nf |
| 176 | |
| 177 | autoexpect \-P ^P \-C ^L \-Q ^Q |
| 178 | |
| 179 | .fi |
| 180 | .SH STYLE |
| 181 | |
| 182 | I don't know if there is a "style" for Expect programs but autoexpect |
| 183 | should definitely not be held up as any model of style. For example, |
| 184 | autoexpect uses features of Expect that are intended specifically for |
| 185 | computer-generated scripting. So don't try to faithfully write |
| 186 | scripts that appear as if they were generated by autoexpect. This is |
| 187 | not useful. |
| 188 | |
| 189 | On the other hand, autoexpect scripts do show some worthwhile things. |
| 190 | For example, you can see how any string must be quoted in order to use |
| 191 | it in a Tcl script simply by running the strings through autoexpect. |
| 192 | |
| 193 | .SH SEE ALSO |
| 194 | .I |
| 195 | "Exploring Expect: A Tcl-Based Toolkit for Automating Interactive Programs" |
| 196 | \fRby Don Libes, |
| 197 | O'Reilly and Associates, January 1995. |
| 198 | .SH AUTHOR |
| 199 | Don Libes, National Institute of Standards and Technology |
| 200 | |
| 201 | .B expect |
| 202 | and |
| 203 | .B autoexpect |
| 204 | are in the public domain. |
| 205 | NIST and I would |
| 206 | appreciate credit if these programs or parts of them are used. |
| 207 | |