OC获取系统日志

1. 获取Log

/*! @header
 * These routines provide an interface to the Apple System Log facility.
 * The API allows client applications to create flexible, structured messages
 * and send them to the syslogd server.  Messages received by the server are
 * saved in a data store, subject to input filtering constraints.
 * This API also permits clients to create queries and search the message
 * data store for matching messages.
 */

#pragma mark - Log Message Fetching

// Due to a mistake in asl.h, things get a little messy. We need to mark these symbols as weak since they won't exist on iOS 7 despite the compiler thinking otherwise.
// asl.h in the iOS 8.1 SDK claims that asl_next() and asl_release() were introduced in iOS 7 to replace aslresponse_next() and aslresponse_free(). However, they were actually added in iOS 8.0.
extern aslmsg asl_next(asl_object_t obj) __attribute__((weak_import));
extern void asl_release(asl_object_t obj) __attribute__((weak_import));

+ (NSArray *)allLogMessagesForCurrentProcess
{
    asl_object_t query = asl_new(ASL_TYPE_QUERY);

    // Filter for messages from the current process. Note that this appears to happen by default on device, but is required in the simulator.
    NSString *pidString = [NSString stringWithFormat:@"%d", [[NSProcessInfo processInfo] processIdentifier]];
    asl_set_query(query, ASL_KEY_PID, [pidString UTF8String], ASL_QUERY_OP_EQUAL);

    aslresponse response = asl_search(NULL, query);
    aslmsg aslMessage = NULL;

    NSMutableArray *logMessages = [NSMutableArray array];

    if (&asl_next != NULL && &asl_release != NULL) {
        while ((aslMessage = asl_next(response))) {
            [logMessages addObject:[SystemLogMessage logMessageFromASLMessage:aslMessage]];
        }
        asl_release(response);
    } else {
        // Mute incorrect deprecated warnings. We'll need the "deprecated" functions on iOS 7, where their replacements don't yet exist.
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
        while ((aslMessage = aslresponse_next(response))) {
            [logMessages addObject:[SystemLogMessage logMessageFromASLMessage:aslMessage]];
        }
        aslresponse_free(response);
#pragma clang diagnostic pop
    }

    return logMessages;
}

在上边用到了logMessageFromASLMessage:这样的一个目录

这个类的原型是

#import <asl.h>

@interface SystemLogMessage : NSObject

+ (instancetype)logMessageFromASLMessage:(aslmsg)aslMessage;

@property (nonatomic, strong) NSDate *date;
@property (nonatomic, copy) NSString *sender;
@property (nonatomic, copy) NSString *messageText;
@property (nonatomic, assign) long long messageID;

@end

#import "SystemLogMessage.h"

@implementation SystemLogMessage

+(instancetype)logMessageFromASLMessage:(aslmsg)aslMessage
{
    SystemLogMessage *logMessage = [[SystemLogMessage alloc] init];

    const char *timestamp = asl_get(aslMessage, ASL_KEY_TIME);
    if (timestamp) {
        NSTimeInterval timeInterval = [@(timestamp) integerValue];
        const char *nanoseconds = asl_get(aslMessage, ASL_KEY_TIME_NSEC);
        if (nanoseconds) {
            timeInterval += [@(nanoseconds) doubleValue] / NSEC_PER_SEC;
        }
        logMessage.date = [NSDate dateWithTimeIntervalSince1970:timeInterval];
    }

    const char *sender = asl_get(aslMessage, ASL_KEY_SENDER);
    if (sender) {
        logMessage.sender = @(sender);
    }

    const char *messageText = asl_get(aslMessage, ASL_KEY_MSG);
    if (messageText) {
        logMessage.messageText = @(messageText);
    }

    const char *messageID = asl_get(aslMessage, ASL_KEY_MSG_ID);
    if (messageID) {
        logMessage.messageID = [@(messageID) longLongValue];
    }

    return logMessage;
}

- (BOOL)isEqual:(id)object
{
    return [object isKindOfClass:[SystemLogMessage class]] && self.messageID == [object messageID];
}

- (NSUInteger)hash
{
    return (NSUInteger)self.messageID;
}

@end

以上部分的参考内容:

1. FLEX框架下的FLEXSystemLogMessage类
   Git地址

查看过的一些代码

1. MWLogging
   Git地址
2. LibComponentLogging
   Git地址