CODEWITHSUNDEEP
objective-cxcodecocoastderr
Biranchi
Biranchi

Reputation: 16327

Trying to read Xcode's console output

My code to read the console in Xcode always gives an error :

read: Bad file descriptor

#include <sys/types.h>
#include <sys/uio.h>
#include <unistd.h>

- (void)viewDidLoad {
    [super viewDidLoad];

    NSLog(@"Some text..."); 

    int fd;
    char ch[1024];
    fd = read(stderr,ch, sizeof(ch));
    if(fd == -1) {
        perror("read");
    } else {
        NSLog(@"Data Read : %s", ch);

    }

}

What is wrong with this?

Upvotes: 2

Views: 1828

Answers (2)

zpasternack
zpasternack

Reputation: 17898

You can't read stderr, but you can redirect it. Like this:

- (void) redirectStandardError
{
    stderrPipe = [NSPipe pipe];
    stderrPipeReadHandle = [stderrPipe fileHandleForReading];
    dup2( [[stderrPipe fileHandleForWriting] fileDescriptor], fileno(stderr));

    [[NSNotificationCenter defaultCenter] addObserver:self 
                                             selector:@selector(handleNotification:) 
                                                 name:NSFileHandleReadCompletionNotification 
                                               object:stderrPipeReadHandle];
    [stderrPipeReadHandle readInBackgroundAndNotify];
}

- (void) handleNotification:(NSNotification*)notification {
    [stderrPipeReadHandle readInBackgroundAndNotify];

    NSString* str = [[NSString alloc] initWithData:[[notification userInfo] objectForKey:NSFileHandleNotificationDataItem] encoding:NSASCIIStringEncoding];

    // Do something with str...

    [str release];
}

Upvotes: 8

Steven Kramer
Steven Kramer

Reputation: 8513

  1. It's highly unlikely that an iPhone app can read from the console, considering there will not be any way to connect an app to pipes or tty's.

  2. It's even unlikelier that it could read from the error file descriptor.

Upvotes: 1

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