Getting a list of files in a directory with a glob

Question

For some crazy reason I can't find a way to get a list of files with a glob for a given directory.

I'm currently stuck with something along the lines of:

NSString *bundleRoot = [[NSBundle mainBundle] bundlePath];
NSArray *dirContents = [[NSFileManager defaultManager] 
                        directoryContentsAtPath:bundleRoot];

..and then stripping out the stuff I don't want, which sucks. But what I'd really like is to be able to search for something like "foo*.jpg" instead of asking for the entire directory, but I've not been able to find anything like that.

So how the heck do you do it?

Answer 1

I won't pretend to be an expert on the topic, but you should have access to both the glob and wordexp function from objective-c, no?

Answer 2

You need to roll your own method to eliminate the files you don't want.

This isn't easy with the built in tools, but you could use RegExKit Lite to assist with finding the elements in the returned array you are interested in. According to the release notes this should work in both Cocoa and Cocoa-Touch applications.

Here's the demo code I wrote up in about 10 minutes. I changed the < and > to " because they weren't showing up inside the pre block, but it still works with the quotes. Maybe somebody who knows more about formatting code here on StackOverflow will correct this (Chris?).

This is a "Foundation Tool" Command Line Utility template project. If I get my git daemon up and running on my home server I'll edit this post to add the URL for the project.

#import "Foundation/Foundation.h"
#import "RegexKit/RegexKit.h"

@interface MTFileMatcher : NSObject 
{
}
- (void)getFilesMatchingRegEx:(NSString*)inRegex forPath:(NSString*)inPath;
@end

int main (int argc, const char * argv[])
{
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    // insert code here...
    MTFileMatcher* matcher = [[[MTFileMatcher alloc] init] autorelease];
    [matcher getFilesMatchingRegEx:@"^.+\\.[Jj][Pp][Ee]?[Gg]$" forPath:[@"~/Pictures" stringByExpandingTildeInPath]];

    [pool drain];
    return 0;
}

@implementation MTFileMatcher
- (void)getFilesMatchingRegEx:(NSString*)inRegex forPath:(NSString*)inPath;
{
    NSArray* filesAtPath = [[[NSFileManager defaultManager] directoryContentsAtPath:inPath] arrayByMatchingObjectsWithRegex:inRegex];
    NSEnumerator* itr = [filesAtPath objectEnumerator];
    NSString* obj;
    while (obj = [itr nextObject])
    {
     NSLog(obj);
    }
}
@end

Answer 3

What about using NSString's hasSuffix and hasPrefix methods? Something like (if you're searching for "foo*.jpg"):

NSString *bundleRoot = [[NSBundle mainBundle] bundlePath];
NSArray *dirContents = [[NSFileManager defaultManager] directoryContentsAtPath:bundleRoot];
for (NSString *tString in dirContents) {
    if ([tString hasPrefix:@"foo"] && [tString hasSuffix:@".jpg"]) {

        // do stuff

    }
}

For simple, straightforward matches like that it would be simpler than using a regex library.

Answer 4

You can achieve this pretty easily with the help of NSPredicate, like so:

NSString *bundleRoot = [[NSBundle mainBundle] bundlePath];
NSArray *dirContents = [[NSFileManager defaultManager] directoryContentsAtPath:bundleRoot];
NSArray *onlyJPGs = [dirContents filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@"self ENDSWITH '.jpg'"]];

Answer 5

Unix has a library that can perform file globbing operations for you. The functions and types are declared in a header called glob.h, so you'll need to #include it. If open up a terminal an open the man page for glob by typing man 3 glob you'll get all of the information you need to know to use the functions.

Below is an example of how you could populate an array the files that match a globbing pattern. When using the glob function there are a few things you need to keep in mind.

1. By default, the glob function looks for files in the current working directory. In order to search another directory you'll need to prepend the directory name to the globbing pattern as I've done in my example to get all of the files in /bin.
2. You are responsible for cleaning up the memory allocated by glob by calling globfree when you're done with the structure.

In my example I use the default options and no error callback. The man page covers all of the options in case there's something in there you want to use. If you're going to use the above code, I'd suggest adding it as a category to NSArray or something like that.

NSMutableArray* files = [NSMutableArray array];
glob_t gt;
char* pattern = "/bin/*";
if (glob(pattern, 0, NULL, &gt) == 0) {
    int i;
    for (i=0; i<gt.gl_matchc; i++) {
        [files addObject: [NSString stringWithCString: gt.gl_pathv[i]]];
    }
}
globfree(&gt);
return [NSArray arrayWithArray: files];

Edit: I've created a gist on github that contains the above code in a category called NSArray+Globbing.

Answer 6

stringWithFileSystemRepresentation doesn't appear to be available in iOS.