Guy's Scripting Ezine 120 - SendKeys

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Guy's Scripting Ezine 120 - SendKeys

• This Week's Secret
• This Week's Mission
• Example 1 - VBScript to issue DIR command in a CMD box
• Example 2 - VBScript SendKeys, Binocular Vision
• Useful List of Special SendKeys commands
• Summary of SendKeys

This Week's Secret

Whenever I review my previous Ezines it always surprises me which ezines are the most popular.  The way I judge popularity is by the number of page hits each ezine receives.  Consistently, SendKeys featured in Ezine 26, wins the popularity stakes by a country mile.  It is because of the level of interest that I am revisiting this topic, in particular I want to be clear when to use SendKeys and when to seek alternative commands.

This Week's Mission

This week I want to put VBScript's SendKeys method into perspective.  As the name indicates, this method literally sends keyboard keystrokes to the interface which is in focus when the script runs.  I suggest that SendKeys has the following three scenarios when it will assist your scripts.

1) SendKeys is great if you just want to have a bit of fun; it's ideal for practising your scripting techniques in a harmless but enjoyable manner.  For example, when you are learning how to open programs such as notepad, with a VBScript, you want some action, therefore you decide to send key strokes to notepad programmatically.

2) SendKeys is handy strategy when you are at an intermediate stage in your scripting project.  You suspect that your script needs some smart scripting switches or program commands, but you just cannot find them.  As a stop-gap measure, until you can research something better, you fall back on SendKeys to issue instructions as though you were typing them at the keyboard.

3) SendKeys as a last resort.  When all else fails, hours of research fails to find that fancy switch, you turn to SendKeys in desperation.  In these circumstances and for the short term, SendKeys will enable you to fulfil your objective, albeit with risky commands.

Professional script writers don't trust SendKeys.  The reason is because the results of sending keystrokes to applications are unpredictable and potentially catastrophic.  Even if no users are involved, factors may change over time and SendKeys instructions may be delivering their keystrokes to entirely the wrong window.  99% of the time such an error will just result in a routine script failure, but there is a slim chance that the keystrokes could cripple the server, or wipe a database.  Professionals would not risk their reputation on SendKeys. 

The only way to see what SendKeys has to offer is to experiment with an example or two.  As a bonus we can use SendKeys as a vehicle to learn valuable techniques, which you can employ in other VBScripts, for example the Set command and the Shell object.

SendKeys Methodology

The methodology is to create our shell object then apply the sendkeys method followed by the keystrokes as a string.  Note the placement of both the brackets and of the speech marks.  You could start with typing these commands into notepad and saving the resultant file with a .vbs extension.  Once you have created Example 1, double click your file and observe SendKeys in action.

Once you have created the shell object then you can send keystrokes to objShell.  However, to be effective, we need our script to launch an application such as notepad or the cmd prompt.

Now we are ready to start sending keys to the CMD prompt session.  In this example we will merely execute a simple "dir" instruction, meaning list the directory contents.

Here is the full script with a few extras such as sleep delays, and a final command to exit the cmd prompt application and close the dos box.

Example 1 - VBScript to issue DIR command in a CMD box

VBScript Learning Points

Note 1:  My use of Sleep to pause the script is contentious.  The reason that I employ this delay to help you trace and understand what is happening.  Professionals say, rightly, that in production scripts you should avoid Sleep commands and instead, let the program handle the timing with their own default routines.  In a nutshell, there is rarely any need for Sleep commands in production scripts.

Note 2:  The Script invokes CMD's own instruction to close, e.g. objShell "Exit".  Observe that the script still needs a carriage return sequence: objShell.SendKeys "{Enter}".  See more special SendKeys instructions at the end of the ezine.

Note 3:  Furthermore, pay special attention to the curly brackets around "{Enter}"

Example 2 - VBScript SendKeys, Binocular Vision

Variation ' set WshShell = WScript.CreateObject("WScript.Shell"). 

By analysing this variation of Example 1, we gain what I call binocular vision. Question: is the tiny word 'set' important?  The answer is yes 'set' is crucial and no, you must not change 'set' to any other verb.

WshShell or objShell what is the difference.  Nothing.  Just a matter of personal choice, which name you use for your, observe how I declare employ Option Explicit to force me to declare all my variables. 

In your scripts, will you use WScript.CreateObject or just plain CreateObject.  I stick with CreateObject because it's shorter, clearer and it always works for me.  Purists may argue that you employ the longer WScript.CreateObject.

Note 1:  I added the variable intSleep so that I can control the pauses between instructions from one place.  Incidentally, a value of 1000 for intSleep means wait one second.

Note 2:  Trace the sub-routine.  Shamelessly, I rarely miss a chance to add a sub-routine to handle repetitive command sequences.  Examine the brackets (), the End Sub, and especially how I call the routine.

Note 3:  For this script I followed through and chose WshShell instead of objShell.  As I mentioned earlier, you can choose what ever name you like for the names of your variables.

If you are looking for handy network utilities, try some of the free downloads at Tools4Ever

Guy's Challenges

Change the value .Sleep time.

Try running other programs, for example .run("NotePad")

Take a view on my sub-routine GuyClose().  My challenge is to rip it out or modify it and thus learn a little about the value of sub-routines.

Useful List of Special SendKeys commands

• BACKSPACE {BACKSPACE}, {BS}, or {BKSP}
• BREAK {BREAK}
• CAPS LOCK {CAPSLOCK}
• DEL or DELETE {DELETE} or {DEL}
• DOWN ARROW {DOWN}
• END {END}
• ENTER {ENTER} or ~
• ESC {ESC}
• HELP {HELP}
• HOME {HOME}
• INS or INSERT {INSERT} or {INS}
• LEFT ARROW {LEFT}
• NUM LOCK {NUMLOCK}
• PAGE DOWN {PGDN}
• PAGE UP {PGUP}
• PRINT SCREEN {PRTSC}
• RIGHT ARROW {RIGHT}
• SCROLL LOCK {SCROLLLOCK}
• TAB {TAB}
• UP ARROW {UP}
• F1 {F1}

Summary of SendKeys

SendKeys is a useful temporary measure for passing keystrokes to your program.  By all means have some fun and learn this aspect of VBScript.  However, for production scripts always favour more reliable techniques.

Guy Thomas recommends Computer Training Software. 

Their topics and material are ideal for getting you started with VBScript.  The videos are easy to follow and you can control the pace.  Try their free demo material and then see if you want to buy the full package. See more about VB Script Training CD.

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