A Simple AppleScript Script

Listing 1 shows an AppleScript script that simply returns the number of files in the Applications folder on the current system disk (denoted by startup disk, a term understood by the Finder). If the folder cannot be found, the script returns a count of zero. This script counts just files in the specified folder, not folders or the files they might contain.

Listing 1  A script that counts the files in the Applications folder

tell application "Finder"

    if folder "Applications" of startup disk exists then

        return count files in folder "Applications" of startup disk

    else

        return 0

    end if

end tell

When a script is compiled and executed, some statements perform basic operations, such as assigning a variable or returning a value. A statement that targets a scriptable application results in an Apple event being sent to that application. The application can return information to the script in a reply Apple event.

The script in Listing 1 causes an Apple event to be sent to the Finder, which locates the Applications folder on the startup disk, counts the files in it, and returns that value. The if...then...else structure is one of several standard programming language features that AppleScript supports.

Script Editor

The Script Editor application is located in /Applications/AppleScript. It provides the ability to edit, compile, and execute scripts, display application scripting terminologies, and save scripts in a variety of formats, such as compiled scripts, applications, bundled applications, and plain text.

Script Editor can display the result of executing an AppleScript script and can display a log of the Apple events that are sent during execution of a script. In the Script Editor Preferences, you can also choose to keep a history of recent results or event logs.

Script Editor has text formatting preferences for various types of script text, such as language keywords, comments, and so on. You can also turn on or off the Script Assistant, a code completion tool that can suggest and fill in scripting terms as you type. In addition, Script Editor provides a contextual menu to insert many types of boilerplate script statements, such as conditionals, comments, and error handlers.

Displaying Scripting Dictionaries

You can choose File > Open Dictionary in Script Editor to examine the scripting dictionary of a scriptable application or scripting addition on your computer. Or you can drag an application icon to the Script Editor icon to display its dictionary (if it has one). You can also open scripting dictionaries in Xcode.

To display a list that includes just the scriptable applications and scripting additions provided by the Mac OS, choose Window > Library. Double-click an item in the list to display its dictionary. Figure 1 shows the dictionary for the Finder application in OS X version 10.5. The dictionary is labeled as “Finder.sdef”. The sdef format, along with other terminology formats, is described in Specifying Scripting Terminology.

Interacting with the User in Scripts

AppleScript provides little direct support for interacting with the user in scripts. However, the Standard Additions scripting addition provides terminology for obtaining various choices from the user. For example, it includes commands for letting the user choose an application, a color, a file, a filename, and so on. It also provides the display dialog command, which allows you to display a dialog with various options for text labels, buttons, and text input. Scripting Additions are described in Extending AppleScript with Coercions, Scripting Additions, and Faceless Background Applications.

Executing Shell Commands From AppleScript Scripts

AppleScript provides the do shell script command to support executing a shell command as part of an AppleScript script. For example, the following script statement uses a do shell script command to change the directory to the current user’s home directory and obtain a list of the files found there. The list information is stored in the AppleScript variable fileInfo:

set fileInfo to do shell script "cd ~; ls"

The do shell script command is primarily of use to scripters. Although applications can execute AppleScript scripts that use the do shell script command, they have more efficient options for executing shell commands, as described in Support for Carbon Applications and Support for Cocoa Applications. For more information on the do shell script command, see Technical Note TN2065, do shell script in AppleScript.

Executing AppleScript Scripts as Shell Commands

To execute AppleScript scripts as shell commands in a Terminal window or shell script file, you can use the osacompile command and the osascript command (located in /usr/bin). The former compiles an AppleScript script, while the latter executes a plain text or a compiled AppleScript script. Man pages provide documentation for these commands. For example, type man osascript in a Terminal window to get information on the osascript command.

Starting in OS X version 10.5, there is a command-line tool to display compiled scripts as text, osadecompile. Again, see the man page for details.

Also starting in Mac OX X v10.5, AppleScript allows use of the # symbol as a comment-to-end-of-line token (the traditional double hyphen (--) is also still supported). This means that you can make a plain AppleScript script into a Unix executable by beginning it with the following line and giving it execute permission.

#!/usr/bin/osascript

Scripting the Terminal Application

The Terminal application is itself scriptable. For example, you can use the do script command to execute text as a shell script or command. To see the operations Terminal supports, you can examine its scripting dictionary with Script Editor.

Using Other Scripting Languages

For those who have experience with various scripting languages and environments, the previous sections have probably already provided an urge to start experimenting. And you do have a lot of options for combining features from the scripting tools, languages, and environments that are most appropriate for specific kinds of tasks. For example, the following one-line shell script statement combines Perl, AppleScript, and various tools to find duplicate entries in the Address Book application.

osascript -e 'tell app "Address Book" to get the name of every person' | perl -pe 's/, /\n/g' | sort | uniq -d

This statement uses osascript to execute an inline AppleScript script ('tell app "Address Book" to get the name of every person') that returns the names of every address entry from the Address Book application. It pipes the output of this script through the perl tool, and with a series of other commands and pipes, obtains and formats a (possibly empty) list of duplicate names.

For additional information about working with AppleScript from languages such as Ruby and Python, see Scripting Bridge.