how to collect system info in osx using objective c

The easiest way is to use the output from the system_profiler command. It also has an -xml option to make the output easy to automatically parse.

The underlying API that I believe System Profiler uses (for at least some of the information it gathers), and that you should use if you want very specific information, is sysctl. It lets you query for individual attributes of the system, including number of CPUs, CPU speed, available RAM, etc.

System Profiler is nice and will output an XML for some slow file I/O and also let's depend on another process to complete before getting the desired information. Well if I put it this way, is System Profiler really the best option and answer for this question? I think not (IMO).

Here is how I do it. The header are readonly properties of the private readwrite properties. The category methods are pretty straight forward, but if anyone has a question then post and I will answer.

#import <IOKit/IOKitLib.h>
#import <sys/sysctl.h>

@interface VarSystemInfo ()
@property (readwrite, strong, nonatomic) NSString *sysName;
@property (readwrite, strong, nonatomic) NSString *sysUserName;
@property (readwrite, strong, nonatomic) NSString *sysFullUserName;
@property (readwrite, strong, nonatomic) NSString *sysOSName;
@property (readwrite, strong, nonatomic) NSString *sysOSVersion;
@property (readwrite, strong, nonatomic) NSString *sysPhysicalMemory;
@property (readwrite, strong, nonatomic) NSString *sysSerialNumber;
@property (readwrite, strong, nonatomic) NSString *sysUUID;
@property (readwrite, strong, nonatomic) NSString *sysModelID;
@property (readwrite, strong, nonatomic) NSString *sysModelName;
@property (readwrite, strong, nonatomic) NSString *sysProcessorName;
@property (readwrite, strong, nonatomic) NSString *sysProcessorSpeed;
@property (readwrite, strong, nonatomic) NSNumber *sysProcessorCount;
@property (readonly,  strong, nonatomic) NSString *getOSVersionInfo;

- (NSString *) _strIORegistryEntry:(NSString *)registryKey;
- (NSString *) _strControlEntry:(NSString *)ctlKey;
- (NSNumber *) _numControlEntry:(NSString *)ctlKey;
- (NSString *) _modelNameFromID:(NSString *)modelID;
- (NSString *) _parseBrandName:(NSString *)brandName;
@end

static NSString* const kVarSysInfoVersionFormat  = @"%@.%@.%@ (%@)";
static NSString* const kVarSysInfoPlatformExpert = @"IOPlatformExpertDevice";

static NSString* const kVarSysInfoKeyOSVersion = @"kern.osrelease";
static NSString* const kVarSysInfoKeyOSBuild   = @"kern.osversion";
static NSString* const kVarSysInfoKeyModel     = @"hw.model";
static NSString* const kVarSysInfoKeyCPUCount  = @"hw.physicalcpu";
static NSString* const kVarSysInfoKeyCPUFreq   = @"hw.cpufrequency";
static NSString* const kVarSysInfoKeyCPUBrand  = @"machdep.cpu.brand_string";

static NSString* const kVarSysInfoMachineNames       = @"MachineNames";
static NSString* const kVarSysInfoMachineiMac        = @"iMac";
static NSString* const kVarSysInfoMachineMacmini     = @"Mac mini";
static NSString* const kVarSysInfoMachineMacBookAir  = @"MacBook Air";
static NSString* const kVarSysInfoMachineMacBookPro  = @"MacBook Pro";
static NSString* const kVarSysInfoMachineMacPro      = @"Mac Pro";

#pragma mark - Implementation:
#pragma mark -

@implementation VarSystemInfo

@synthesize sysName, sysUserName, sysFullUserName;
@synthesize sysOSName, sysOSVersion;
@synthesize sysPhysicalMemory;
@synthesize sysSerialNumber, sysUUID;
@synthesize sysModelID, sysModelName;
@synthesize sysProcessorName, sysProcessorSpeed, sysProcessorCount;

#pragma mark - Helper Methods:

- (NSString *) _strIORegistryEntry:(NSString *)registryKey {

    NSString *retString;

    io_service_t service =
    IOServiceGetMatchingService( kIOMasterPortDefault,
                                 IOServiceMatching([kVarSysInfoPlatformExpert UTF8String]) );
    if ( service ) {

        CFTypeRef cfRefString =
        IORegistryEntryCreateCFProperty( service,
                                         (__bridge CFStringRef)registryKey,
                                         kCFAllocatorDefault, kNilOptions );
        if ( cfRefString ) {

            retString = [NSString stringWithString:(__bridge NSString *)cfRefString];
            CFRelease(cfRefString);

        } IOObjectRelease( service );

    } return retString;
}

- (NSString *) _strControlEntry:(NSString *)ctlKey {

    size_t size = 0;
    if ( sysctlbyname([ctlKey UTF8String], NULL, &size, NULL, 0) == -1 ) return nil;

    char *machine = calloc( 1, size );

    sysctlbyname([ctlKey UTF8String], machine, &size, NULL, 0);
    NSString *ctlValue = [NSString stringWithCString:machine encoding:[NSString defaultCStringEncoding]];

    free(machine); return ctlValue;
}

- (NSNumber *) _numControlEntry:(NSString *)ctlKey {

    size_t size = sizeof( uint64_t ); uint64_t ctlValue = 0;
    if ( sysctlbyname([ctlKey UTF8String], &ctlValue, &size, NULL, 0) == -1 ) return nil;
    return [NSNumber numberWithUnsignedLongLong:ctlValue];
}

- (NSString *) _modelNameFromID:(NSString *)modelID {

    /*!
     * @discussion Maintain Machine Names plist from the following site
     * @abstract ref: http://www.everymac.com/systems/by_capability/mac-specs-by-machine-model-machine-id.html
     *
     * @discussion Also info found in SPMachineTypes.plist @ /System/Library/PrivateFrameworks/...
     *             ...AppleSystemInfo.framework/Versions/A/Resources
     *             Information here is private and can not be linked into the code.
     */

    NSDictionary *modelDict = [[NSBundle mainBundle] URLForResource:kVarSysInfoMachineNames withExtension:@"plist"].serialPList;
    NSString *modelName = [modelDict objectForKey:modelID];

    if ( !modelName ) {

        if ( [modelID.lowercaseString hasPrefix:kVarSysInfoMachineiMac.lowercaseString] ) return kVarSysInfoMachineiMac;
        else if ( [modelID.lowercaseString hasPrefix:kVarSysInfoMachineMacmini.noWhitespaceAndLowerCaseString] )    return kVarSysInfoMachineMacmini;
        else if ( [modelID.lowercaseString hasPrefix:kVarSysInfoMachineMacBookAir.noWhitespaceAndLowerCaseString] ) return kVarSysInfoMachineMacBookAir;
        else if ( [modelID.lowercaseString hasPrefix:kVarSysInfoMachineMacBookPro.noWhitespaceAndLowerCaseString] ) return kVarSysInfoMachineMacBookPro;
        else if ( [modelID.lowercaseString hasPrefix:kVarSysInfoMachineMacPro.noWhitespaceAndLowerCaseString] )     return kVarSysInfoMachineMacPro;
        else return modelID;

    } return modelName;
}

- (NSString *) _parseBrandName:(NSString *)brandName {

    if ( !brandName ) return nil;

    NSMutableArray *newWords = [NSMutableArray array];
    NSString *strCopyRight = @"r", *strTradeMark = @"tm", *strCPU = @"CPU";

    NSArray *words = [brandName componentsSeparatedByCharactersInSet:[[NSCharacterSet alphanumericCharacterSet] invertedSet]];

    for ( NSString *word in words ) {

        if ( [word isEqualToString:strCPU] )       break;
        if ( [word isEqualToString:@""] )          continue;
        if ( [word.lowercaseString isEqualToString:strCopyRight] ) continue;
        if ( [word.lowercaseString isEqualToString:strTradeMark] ) continue;

        if ( [word length] > 0 ) {

            NSString *firstChar = [word substringToIndex:1];
            if ( NSNotFound != [firstChar rangeOfCharacterFromSet:[NSCharacterSet decimalDigitCharacterSet]].location ) continue;

            [newWords addObject:word];

    } } return [newWords componentsJoinedByString:@" "];
}

- (NSString *) getOSVersionInfo {

    NSString *darwinVer = [self _strControlEntry:kVarSysInfoKeyOSVersion];
    NSString *buildNo = [self _strControlEntry:kVarSysInfoKeyOSBuild];
    if ( !darwinVer || !buildNo ) return nil;

    NSString *majorVer = @"10", *minorVer = @"x", *bugFix = @"x";
    NSArray *darwinChunks = [darwinVer componentsSeparatedByCharactersInSet:[NSCharacterSet punctuationCharacterSet]];

    if ( [darwinChunks count] > 0 ) {

        NSInteger firstChunk = [(NSString *)[darwinChunks objectAtIndex:0] integerValue];
        minorVer = [NSString stringWithFormat:@"%ld", (firstChunk - 4)];
        bugFix = [darwinChunks objectAtIndex:1];
        return [NSString stringWithFormat:kVarSysInfoVersionFormat, majorVer, minorVer, bugFix, buildNo];

    } return nil;
}

#pragma mark - Initalization:

- (void) setupSystemInformation {

    NSProcessInfo *pi = [NSProcessInfo processInfo];

    self.sysName = [[NSHost currentHost] localizedName];
    self.sysUserName = NSUserName();
    self.sysFullUserName = NSFullUserName();
    self.sysOSName = pi.strOperatingSystem;
    self.sysOSVersion = self.getOSVersionInfo;
    self.sysPhysicalMemory = [[NSNumber numberWithUnsignedLongLong:pi.physicalMemory] strBinarySizeMaxFractionDigits:0];
    self.sysSerialNumber = [self _strIORegistryEntry:(__bridge NSString *)CFSTR(kIOPlatformSerialNumberKey)];
    self.sysUUID = [self _strIORegistryEntry:(__bridge NSString *)CFSTR(kIOPlatformUUIDKey)];
    self.sysModelID = [self _strControlEntry:kVarSysInfoKeyModel];
    self.sysModelName = [self _modelNameFromID:self.sysModelID];
    self.sysProcessorName = [self _parseBrandName:[self _strControlEntry:kVarSysInfoKeyCPUBrand]];
    self.sysProcessorSpeed = [[self _numControlEntry:kVarSysInfoKeyCPUFreq] strBaseTenSpeedMaxFractionDigits:2];
    self.sysProcessorCount = [self _numControlEntry:kVarSysInfoKeyCPUCount];
}

- (id) init {

    if ( (self = [super init]) ) {

        [self setupSystemInformation];

    } return self;
}

@end

Enjoy!

P.S. I load all the property values during init so as to avoid multiple system calls && because its cheap && all values should be fairly static.

P.P.S. I also load a MachineNames plist that I created, but I know its my own process only that has access to it and the comment describes where I get the information.