Mac Automation Scripting Guide: Calling Command-Line Tools

Calling Command-Line Tools

In AppleScript, the do shell script command is used to execute command-line tools. This command is implemented by the Standard Additions scripting addition included with OS X.

Executing Commands

The direct parameter of the do shell script command is a string containing the shell code you want to execute, as demonstrated in Listing 39-1, which simply lists a directory.

APPLESCRIPT

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Listing 39-1AppleScript: Executing a simple shell command that lists the contents of a directory

do shell script "ls /Applications/"
(*
--> Result:
"App Store.app
Automator.app
Calculator.app
Calendar.app
..."
*)

Since the direct parameter of do shell script is a string, you can concatenate it with other strings at run time. Listing 39-2, for example, concatenates a shell command to a previously defined parameter value.

APPLESCRIPT

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Listing 39-2AppleScript: Concatenating a command with a value

set theHostName to "www.apple.com"
do shell script "ping -c1 " & theHostName

Quoting Strings

The shell uses space characters to separate parameters and gives special meaning to certain punctuation marks, such as $, (, ), and *. To ensure that strings are treated as expected—for example, spaces aren’t seen as delimiters—it’s best to wrap strings in quotes. This process is known as quoting. If your string contains quotes, they must also be escaped (preceded by a / character) so they are interpreted as part of the string. Listing 39-3 shows an example of an error occurring as a result of a parameter that contains a space.

APPLESCRIPT

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Listing 39-3AppleScript: An error resulting from a string containing a space

set thePath to "/Library/Application Support/"
do shell script "ls " & thePath
--> Result: error "ls: /Library/Application: No such file or directory\rls: Support: No such file or directory" number 1

The easiest way to quote a string is to use the quoted form property of the text class, as demonstrated in Listing 39-4. This property returns the string in a form that’s safe from further interpretation by the shell, regardless of its contents.

APPLESCRIPT

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Listing 39-4AppleScript: Quoting a string to prevent errors

set thePath to quoted form of "/Library/Application Support/"
--> Result: "'/Library/Application Support/'"
do shell script "ls " & thePath
(*
--> Result:
"App Store
Apple
...
"
*)

More Information

For more information about the do shell script command, see Commands Reference in AppleScript Language Guide and Technical Note TN2065.

Manipulating Images

Making a Systemwide Service