- Terminal 101: Using the Find Command
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Folks- I'm hitting a brick wall here. I need to test for the existence of a file in a folder, and it could be nested within a subfolder one level deep.
The file would contain the string "wrt. I haven't yet touched on trying to search within a folder nested within a folder Plus, a string will always exist. Oops: It looks like this may actually be a bug in AppleScript, according to hhas below. It completely fooled me, because the behaviour is logical and explainable. Please read hhas's post below. I would like to expand on this, since newcomers typically don't know what's going on here. I don't think I've seen it discussed in detail before on the forums, but I haven't searched for it, so I may be retreading.
First, some background. Strings are not an exception, and in fact they're a really good example to get us going and lay some foundation work. What's the difference between dynamically and statically allocated strings? You typed the string into the source code, so the compiler knows exactly how long, in memory, the value of the variable needs to be; you've essentially told the compiler how much data the program will need to store in memory by defining the exact string, and thus its length.
Compilers are smart that way--since they know how large certain data types are, they can figure out certain optimizations when given the right information. Such as an exact string typed into the source. In C, for example, "pants" is exactly 6 bytes long. Five characters plus one null character to mark the end of the string. It will always be 6 bytes long when the program loads, so the compiler can gain a tiny resource gain by shoving those 6 bytes into an unchanging--static--memory location.
The first version, however, requires the user to choose a file. The compiler has no way to know what file the user will choose, so it can't make the same kind of optimization--the user might pick a path whose length is 26 bytes, 67 bytes, or bytes. Because of this, we say it's dynamically allocated.
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We're going to move away from strings for just a moment, so follow along. You don't really know how it works internally--it's part of a larger library you're using--and it doesn't really matter. You just know that using the command will either return you some object or result in nothing at all. If the window object exists, you'll fall through the branch and call doStuff.
If not, you'll skip past and continue executing code. It doesn't know what paths, folders, disks, songs, windows, or other things are specifically. It's the difference between asking a road map if Iowa exists and actually going to Iowa and seeing what's there. The map might tell you that yes, Iowa exists, but then you look to see what Iowa is, and it's actually a giant amusement park 3 miles wide, instead of a mid-sized U.
Terminal 101: Using the Find Command
You: "Does Iowa exist? Ask an application that understands what roads and states are. But I'll tell you 'yes' anyway. Because even when I don't have the file, I've still typed that string directly into the source code. It isn't going to change, so the compiler statically allocates an AppleScript string object for it.
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And that is why "exists" always says something exists when you specify a string in your code in AppleScript. Thanks for posting that.
Keep posting great stuff like that and sooner or later Adam or Ray will ask you why you're not writing articles Nitewing '98 -- I distrust morning people, largely because I suspect them of getting together early one day while the rest of us were asleep and setting up the rules of civilization. Hate to say this, but your explanation is incorrect. It isn't an AppleScript command, and AppleScript will raise a 'does not understand' error if it tries to handle it itself. What you're actually seeing is a result of a bug in Script Editor: the default 'exists' command provided by the Cocoa Scripting framework should raise a type error if passed a non-reference value, but incorrectly returns a result instead.
Feel free to file a bug report on this. To demonstrate, try running the script in Smile which implements the 'exists' command correctly, and so raises an 'expected a reference' error or in osascript which doesn't implement an 'exists' command, and so raises a 'does not understand' error. DOS Expressions. Drop down list settings. End of string.
Finding and replacing characters using wildcards
Ends with. Enhanced Document Searching. Escape character. Example escape character. Example using Example using.
Example using [ Examples for occurrence characters. Exclude expression. Expert user. Export Results. Expression Types. Expression Wizard. File contents. File list view. File name options. File save. Folder settings. Followed by. Getting started. Hiding contents view. History settings.
How do you use Agent Ransack. Introduction to Regular Expressions. Knowledge base. List of special characters used in Regular Expression. Load last search on startup. Log file location. Long line processing settings. Look in. Mac files. Main Tab. Match case. Max End of Line settings. Multiple file types. Multiple folders. NOT Boolean expression. Occurrence characters. One Phase Searching. Options Tab. OR Boolean expression. Perl regular expressions.
Quick start. Regular Expression basics. Regular Expression Introduction. Regular expression setting. Right click. Save Results. Search Wizard.
Searching directly to file.