Let's say I want to run curl -o http://example.com/file.zip via an Objective C app and I want to have a label or text box containing the download status which gets updated while the command is running. Maybe this could be achieved using dispatch_async, but now sure how. Before marking as duplicate, the methods I found, run the command, and after it has finished you get the output. I want to get the output while it's running, kinda like a terminal emulator.
You need to connect a NSPipe to the NSTask using the standardOutput property and register to receive Data Available notifications.
#interface TaskMonitor: NSObject
#property NSPipe *outputPipe;
#end
#implementation TaskMonitor
-(void)captureStandardOutput:(NSTask *)process {
self.outputPipe = [NSPipe new];
process.standardOutput = self.outputPipe;
//listen for data available
[self.outputPipe.fileHandleForReading waitForDataInBackgroundAndNotify];
[[NSNotificationCenter defaultCenter] addObserverForName:NSFileHandleDataAvailableNotification object:self.outputPipe.fileHandleForReading queue:nil usingBlock:^(NSNotification * _Nonnull note) {
NSData *output = self.outputPipe.fileHandleForReading.availableData;
NSString *outputString = [[NSString alloc] initWithData:output encoding:NSUTF8StringEncoding];
dispatch_async(dispatch_get_main_queue(), ^{
// do something with the string chunk that has been received
NSLog(#"-> %#",outputString);
});
//listen again...
[self.outputPipe.fileHandleForReading waitForDataInBackgroundAndNotify];
}];
}
#end
Related
Since Mavericks, OS X introduced tags in the Finder.
I'd like to know if there is any easy way to search for all files with a given tag.
For example, get all the files (possibly within a certain directory) that are tagged with "Favorite".
I know I can get the tags off an individual file using NSURL. Using that I could just query the entire file system myself by iterating over directories and files.
But I'm wondering if the Objective C API has a faster way to do it.
Thank you #Volker. That got me on the right path.
(But only after I spent three hours writing a framework that would iterate over each and every file checking to see if it matched the tag, which is an extravagantly inefficient way to do it.)
So, here's a class that will search and return all files marked with a given tag.
FindTaggedFiles.h
#interface FindTaggedFiles : NSObject
{
#private NSString* _tag;
#private NSMetadataQuery* query;
}
-(id)initWithTag:(NSString*)tag withHandler:(void(^)(NSArray*))handler;
-(void)startSearch;
#end
FindTaggedFiles.m
#interface FindTaggedFiles()
#property (copy) void (^completionHandler)(NSArray*);
#end
#implementation FindTaggedFiles
-(id)initWithTag:(NSString *)tag withHandler:(void (^)(NSArray *))handler
{
self = [super init];
_completionHandler = handler;
self->_tag = tag;
return self;
}
-(void)startSearch
{
query = [[NSMetadataQuery alloc]init];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(queryDidUpdate:) name:NSMetadataQueryDidUpdateNotification object:query];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(initalGatherComplete:) name:NSMetadataQueryDidFinishGatheringNotification object:query];
NSPredicate *searchPredicate;
NSString* predicate = [NSString stringWithFormat:#"kMDItemUserTags == '%#'", self->_tag ];
searchPredicate=[NSPredicate predicateWithFormat:predicate];
[query setPredicate:searchPredicate];
NSArray *searchScopes;
searchScopes=[NSArray arrayWithObjects:NSMetadataQueryUserHomeScope,nil];
[query setSearchScopes:searchScopes];
NSSortDescriptor *sortKeys=[[NSSortDescriptor alloc] initWithKey:(id)kMDItemDisplayName ascending:YES];
[query setSortDescriptors:[NSArray arrayWithObject:sortKeys]];
[query startQuery];
}
- (void)queryDidUpdate:sender;
{
NSLog(#"A data batch has been received");
}
- (void)initalGatherComplete:sender;
{
[query stopQuery];
NSMutableArray* files = [[NSMutableArray alloc]init];
NSUInteger i=0;
for (i=0; i < [query resultCount]; i++) {
NSMetadataItem *theResult = [query resultAtIndex:i];
[files addObject:theResult];
}
[[NSNotificationCenter defaultCenter] removeObserver:self name:NSMetadataQueryDidUpdateNotification object:query];
[[NSNotificationCenter defaultCenter] removeObserver:self name:NSMetadataQueryDidFinishGatheringNotification object:query];
self->query=nil;
_completionHandler(files);
}
Then you would use it like this
FindTaggedFiles* finder = [[FindTaggedFiles alloc]initWithTag:#"Disneyland" withHandler:^(NSArray* files){
//do something with the files
}];
[finder startSearch];
The NSMetaDataQuery works asynchronously, so I designed this class to require an async block as handler code in the init method. But, in the documentation, I believe it mentions that you don't have to run the search async.
My class is an adaptation of the code in the Apple documentation.
Also note: this doesn't search within a specific directory as such. The meta data query runs in a specific scope. A scope can be the user's home directory (like in this example), the user's iCloud, all attached drives, and a couple others. The specifics are covered in the documentation I linked to just above under "Limiting the search scope".
I believe you could further customize the query to limit it to a directory.
I'm working on this app that launches other apps. I'm listening to app launches using:
[[[NSWorkspace sharedWorkspace] notificationCenter] addObserver:self
selector:#selector(appLaunched:) name:NSWorkspaceDidLaunchApplicationNotification
object:nil];
And I launch them using (Mail is just an example):
NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:[NSArray arrayWithObject:#"lalalala"], NSWorkspaceLaunchConfigurationArguments, nil];
[[NSWorkspace sharedWorkspace] launchApplicationAtURL:[NSURL URLWithString:#"/Applications/Mail.app"] options:NSWorkspaceLaunchWithoutActivation configuration:dict error:nil];
I did some research, and I saw that you can send an argument when you launch an app (that's why I used the var dict in the code above), but I'm having an issue with this: even using NSWorkspaceLaunchWithoutActivation, the Mail.app is launched and becomes focused with a new composing window. I don't know why it's doing that.
Another thing, if I manage to successfully send a custom argument without focusing the app, how can I check if the app was launched by me (check if the argument is there)?
PS: I'm looking for App Store-ready methods.
Send the timestamp (UTC) together with the app name you started to your server or a local file if possible.
Then you can track it.
Firstly, I'd try NSWorkspaceLaunchAndHide if NSWorkspaceLaunchWithoutActivation isn't "working". Not ideal, no.. but a kludge...
Secondly... here's a "full, running example" that does the trick..
#import <Cocoa/Cocoa.h>
NSString *psAUX(NSString*grep) {
FILE *read_f; char buff[BUFSIZ+1]; int char_rd; NSString *res, *cmnd;
memset(buff, '\0', sizeof(buff));
cmnd = [NSString stringWithFormat:#"/bin/ps aux|grep -i %#",grep];
read_f = popen(cmnd.UTF8String, "r");
if (read_f == NULL) return nil;
char_rd = fread(buff, sizeof(char), BUFSIZ, read_f);
if (!char_rd) return nil;
return res = [NSString stringWithUTF8String:buff], pclose(read_f), res;
}
int main(int argc, char *argv[]) { #autoreleasepool {
NSString* secretStr; NSURL *mailURL; NSDictionary *cfg; NSWorkspace *ws; NSApplication.sharedApplication;
secretStr = #"TAMPAX";
mailURL = [NSURL URLWithString:#"file:///Applications/Mail.app"];
cfg = #{NSWorkspaceLaunchConfigurationArguments:#[secretStr]};
ws = NSWorkspace.sharedWorkspace;
[ws launchApplicationAtURL:mailURL options:0 configuration:cfg error:nil];
fprintf(stderr,"%s",
[psAUX(#"Mail.app") containsString:secretStr]
? "You ARE Mail's baby's daddy!"
: "Hands off, she's NOT yours!");
[NSApp run]; } }
NSLog -> You ARE Mail's baby's daddy!
Congratulations!
You can create a new Task using NSTask. With NSTask you can set arguments as well as some environment variables to app so that you can check if it is launched by you or by someone else.
Here is the sample code sniffet to do so:
NSTask* taskApp = [[NSTask alloc] init];
[taskApp setLaunchPath:#"App path goes here"];
[taskApp setArguments:[NSArray arrayWithObjects:#"Arg1",#"arg2", nil]];
[taskApp setEnvironment: [[NSProcessInfo processInfo] environment]];
[taskApp launch];
I've been trying to make do (see this and this) with the recent NSUserScriptTask class and its subclasses and so far I've solved some problems, but some others remain to be solved. As you can see from the docs, NSUserScriptTask does not allow for the cancellation of tasks. So, I decided to create a simple executable that takes as arguments the path to the script and runs the script. That way, I can launch the helper from my main app using NSTask and call [task terminate] when necessary. However, I require:
The main app to receive output and errors from the helper it launched
The helper only terminating when the NSUserScriptTask is done
The code for the main app is simple: just launch an NSTask with the proper info. Here's what I have now (for the sake of simplicity I ignored the code for security-scoped bookmarks and the like, which are out of the problem. But don't forget this is running sandboxed):
// Create task
task = [NSTask new];
[task setLaunchPath: [[NSBundle mainBundle] pathForResource: #"ScriptHelper" ofType: #""]];
[task setArguments: [NSArray arrayWithObjects: scriptPath, nil]];
// Create error pipe
NSPipe* errorPipe = [NSPipe new];
[task setStandardError: errorPipe];
// Create output pipe
NSPipe* outputPipe = [NSPipe new];
[task setStandardOutput: outputPipe];
// Set termination handler
[task setTerminationHandler: ^(NSTask* task){
// Save output
NSFileHandle* outFile = [outputPipe fileHandleForReading];
NSString* output = [[NSString alloc] initWithData: [outFile readDataToEndOfFile] encoding: NSUTF8StringEncoding];
if ([output length]) {
[output writeToFile: outputPath atomically: NO encoding: NSUTF8StringEncoding error: nil];
}
// Log errors
NSFileHandle* errFile = [errorPipe fileHandleForReading];
NSString* error = [[NSString alloc] initWithData: [errFile readDataToEndOfFile] encoding: NSUTF8StringEncoding];
if ([error length]) {
[error writeToFile: errorPath atomically: NO encoding: NSUTF8StringEncoding error: nil];
}
// Do some other stuff after the script finished running <-- IMPORTANT!
}];
// Start task
[task launch];
Remember, I need the termination handler to only run when: (a) the task was cancelled (b) the task terminated on its own because the script finished running.
Now, on the helper side things start to get hairy, at least for me. Let's imagine for the sake of simplicity that the script is an AppleScript file (so I use the NSUserAppleScriptTask subclass - on the real world I'd have to accomodate for the three types of tasks). Here's what I got so far:
int main(int argc, const char * argv[])
{
#autoreleasepool {
NSString* filePath = [NSString stringWithUTF8String: argv[1]];
__block BOOL done = NO;
NSError* error;
NSUserAppleScriptTask* task = [[NSUserAppleScriptTask alloc] initWithURL: [NSURL fileURLWithPath: filePath] error: &error];
NSLog(#"Task: %#", task); // Prints: "Task: <NSUserAppleScriptTask: 0x1043001f0>" Everything OK
if (error) {
NSLog(#"Error creating task: %#", error); // This is not printed
return 0;
}
NSLog(#"Starting task");
[task executeWithAppleEvent: nil completionHandler: ^(NSAppleEventDescriptor *result, NSError *error) {
NSLog(#"Finished task");
if (error) {
NSLog(#"Error running task: %#", error);
}
done = YES;
}];
// Wait until (done == YES). How??
}
return 0;
}
Now, I have three questions (which are the ones I want to ask with this SO entry). Firstly, "Finished task" never gets printed (the block never gets called) because the task never even starts executing. Instead, I get this on my console:
MessageTracer: msgtracer_vlog_with_keys:377: odd number of keys (domain: com.apple.automation.nsuserscripttask_run, last key: com.apple.message.signature)
I tried running the exact same code from the main app and it completes without a fuss (but from the main app I lose the ability to cancel the script).
Secondly, I only want to reach the end of main (return 0;) after the completion handler is called. But I have no idea how to do that.
Thridly, whenever there's an error or output from the helper I want to send that error/output back to the app, which will receive them through the errorPipe/outputPipe. Something like fprintf(stderr/stdout, "string") does the trick, but I'm not sure if it is the right way to do it.
So, in short, any help regarding the first and second problems is appreciated. The third one I just want to make sure that's how I'm supposed to do it.
Thanks
Question 1: The sub-task doesn't run because its parent exits immediately. (The log message about "odd number of keys" is a bug in NSUserScriptTask, and happens because your helper doesn't have a bundle identifier, but is otherwise harmless and irrelevant to your problem.) It exits immediately because it's not waiting for the completion block to fire, which brings us to...
Question 2: How do you wait for an asynchronous completion block? This has been answered elsewhere, including Wait until multiple networking requests have all executed - including their completion blocks, but to recap, use dispatch groups, something like this:
dispatch_group_t g = dispatch_group_create();
dispatch_group_enter(g);
[task executeWithAppleEvent:nil completionHandler:^(NSAppleEventDescriptor *result, NSError *e) {
...
dispatch_group_leave(g);
}];
dispatch_group_wait(g, DISPATCH_TIME_FOREVER);
dispatch_release(g);
This same pattern works for any call that has a completion block you want to wait for. If you wanted another notification when the group finishes instead of waiting for it, use dispatch_group_notify instead of dispatch_group_wait.
As a side note, the way you’re testing error after allocating the NSUserAppleScriptTask is incorrect. The value of error is defined if and only if the function result is nil (or NO, or whatever indicates failure). If the function succeeds (which you know if it returns non-nil), then error may be anything -- the function may set it to nil, it may leave it undefined, it may even fill it in with a real object. (See also What's the Point of (NSError**)error?)
this is my first post, so let me send me many thanks to all the posting guys
outside there (I use SO extensively passively - great!)
I'm working on an video exporting tool for Mac OS X using the good old Quicktime API.
Brief:
I cut frames from multiple input movies an arrange them (scaled) to a new output
movie (kind of media-kiosk).
As many of the needed QT functionality (e.g. writing timecode ...) need to be
nested in a 32-bit Application, I decided to do this offline using a 32 bit command line
tool. The tool renders frame by frame (offline) and prints the current progress
in values between 0.0 and 1.0
It is invoked by the main application (Cocoa, GUI, the modern stuff) via
NSTask. The stout is caught by a NSPipe.
I took a look at some examples and 'll give you quick overview over my code:
NSTask *task;
NSPipe *pipe;
float progress;
// prepare the offline process
//
//
-(void) prepareOfflineExport {
task = [[NSTask alloc] init];
pipe = [[NSPipe alloc] init];
[task setLaunchPath:pathToRenderer];
[task setStandardOutput:pipe];
}
// arguments are passed outside
// invoke the process
//
-(void) startOfflineExport {
progress = 0.0f;
NSArray *argv = [NSArray arrayWithObjects: /* command line args */, nil];
[task setArguments:argv];
NSFileHandle *fh = [pipe fileHandleForReading];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(dataReady:) name:NSFileHandleReadCompletionNotification object:fh];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(taskTerminated:) name:NSTaskDidTerminateNotification object:task];
[task launch];
[fh readInBackgroundAndNotify];
}
// called when data ready
//
//
-(void) dataReady:(NSNotification*)n {
NSData *d = [[n userInfo] valueForKey:NSFileHandleNotificationData];
if([d length]) {
NSString *s = [[NSString alloc] initWithData:d encoding:NSUTF8StringEncoding];
progress = [s floatValue];
}
}
// called when process exits
//
//
-(void) taskTerminated:(NSNotification*)n {
task = nil;
progress = 1.0f;
}
Now the Problem:
When launching the application inside Xcode (via "run"), everything works fine.
The Invocation is done proper, the process is visible in the activity monitor and
the NSLevelIndicator (on the guy of the innovating app) is proceeding well according
the (float) progress variable.
BUT: if i "archive" the application and execute it outside of Xcode, the stdout of my
Command Line Tool never seem to reach the application. I tried writing a debug file
in
-(void) dataReady:(NSNotification*)n
No chance, it is never called! I tested the issue on several Macs, same problem...
Did I make an obvious mistake or is there some preferences to configure (Sandboxing is off),
maybe known issues that I overlooked?
Thank you for help
Greetings
Mat
I have a situation that I receive a byte data through Web Services request and want to write it to a file on my iOS device. I used to append all data (till end of data) in a memory variable and at the end writing the data using NSStream to a file in my iOS device using method:
stream:(NSStream *)theStream handleEvent:(NSStreamEvent)streamEvent
It works fine for small size of data, but the problem is if I am receiving data via web services it could be a big chunk (couple MBs) and I don't want to collect all in memory to write it to the file, to make it efficent I think I have to switch to NSFileHandle to write data in a small chunk size to the same file in several times. Now my question is what is the best approach to do this? I mean how can I do write to the file in BACKGROUND using NSFileHandle? I use code like this:
- (void) setUpAsynchronousContentSave:(NSData *) data {
NSString *newFilePath = [NSHomeDirectory() stringByAppendingPathComponent:#"/Documents/MyFile.xml"];
if(![[NSFileManager defaultManager] fileExistsAtPath:newFilePath ]) {
[[NSFileManager defaultManager] createFileAtPath:newFilePath contents:nil attributes:nil];
}
if(!fileHandle_writer) {
fileHandle_writer = [NSFileHandle fileHandleForWritingAtPath:newFilePath];
}
[fileHandle_writer seekToEndOfFile];
[fileHandle_writer writeData:data];
}
but with passing a data size of 1-2 Mb to above method, do I need to make it running in background? FYI I'm writing in main thread.
Maybe you can try Grand Central Dispatch.
I spent some time trying it, bellow is my way to do it.
According to Apple's document, if our program need executing only one task at a time, we should create a "Serial Dispatch Queue".So, first declare a queue as iVar.
dispatch_queue_t queue;
create a serial dispatch queue in init or ViewDidLoad using
if(!queue)
{
queue = dispatch_queue_create("yourOwnQueueName", NULL);
}
When data occurs, call your method.
- (void) setUpAsynchronousContentSave:(NSData *) data {
NSString *newFilePath = [NSHomeDirectory() stringByAppendingPathComponent:#"/Documents/MyFile.xml"];
NSFileManager *fileManager = [[NSFileManager alloc] init];
if(![fileManager fileExistsAtPath:newFilePath ]) {
[fileManager createFileAtPath:newFilePath contents:nil attributes:nil];
}
if(!fileHandle_writer) {
self.fileHandle_writer = [NSFileHandle fileHandleForWritingAtPath:newFilePath];
}
dispatch_async( queue ,
^ {
// execute asynchronously
[fileHandle_writer seekToEndOfFile];
[fileHandle_writer writeData:data];
});
}
At last, we need to release the queue in ViewDidUnload or dealloc
if(queue)
{
dispatch_release(queue);
}
I combine these code with ASIHttp, and it works.
Hope it helps.