Question

I’ve got an NSTask that uses a piped grep command; The output matches, and grep comes back with a match to my input string — although when comparing it back to the original string it doesn’t match somehow. I’m probably not comparing the returned string properly against the other one? please help.

NSString* filePath = [NSHomeDirectory() stringByAppendingPathComponent:@"/path/to/file"];

NSTask *task;
        task = [[NSTask alloc] init];
        [task setLaunchPath: @"/usr/bin/grep"];

NSString *words = @"words";

NSArray *arguments;
        arguments = [NSArray arrayWithObjects: @"-o", "-a", "-m 1", @"-h", @"-r", words, filePath, nil];

        [task setArguments: arguments];

NSPipe *pipe;
        pipe = [NSPipe pipe];
        [task setStandardOutput: pipe];

NSFileHandle *file;
        file = [pipe fileHandleForReading];

        [task launch];

NSData *data;
        data = [file readDataToEndOfFile];

NSString *string;
        string = [[NSString alloc] initWithData: data encoding: NSUTF8StringEncoding];

NSLog (@"grep returned:\n%@", string);
NSLog (@"grep searched:\n%@", words);

    [task release];

if ([string isEqualToString:words]) {
    NSLog(@"match: %@", string);
} else {
    NSLog(@"failed");

    [string release];

It fails with the output in console looking like this:

grep returned:
words
grep searched:
words
failed

Answer 1

I believe grep prints a newline after its output, so it would return “words\n” while your string is just “words”.