获取进程启动时间

详情请参考 iOS Application launch time on device
我们知道在调试的时候通过设置环境变量DYLD_PRINT_STATISTICS 可以在调试窗口输出main函数前的耗时.

image.png
有没有办法通过API获取呢?以下就是方案之一

#include "LaunchTimeMeasurer.h"
#include <sys/sysctl.h>;
#include <sys/unistd.h>;
double processUptime() {
    struct timeval currentTime; // 1
    struct kinfo_proc processInfo // 2;
    size_t processInfoSize = sizeof(processInfo) // 3;
    int mib[] = {CTL_KERN, KERN_PROC, KERN_PROC_PID, getpid()}; // 4
    
    sysctl(mib, sizeof(mib)/sizeof(int), &processInfo, &processInfoSize, NULL, 0); // 5
    gettimeofday(&amp;currentTime, NULL); // 6
    
    return toSeconds(currentTime) - toSeconds(processInfo.kp_proc.p_starttime); // 7
}
double toSeconds(struct timeval time) {
    const int microsecondsInSecond = 1000000;
    return time.tv_sec + (double)time.tv_usec / microsecondsInSecond;
}

• sysctl

1. CTL_KERN — “high kernel”: proc, limits
2. KERN_PROC — process entries
3. KERN_PROC_PID — filter by id of process
4. getpid() — id of current process

+ (BOOL)processInfoForPID:(int)pid procInfo:(struct kinfo_proc *)procInfo
{
    int cmd[4] = {CTL_KERN, KERN_PROC, KERN_PROC_PID, pid};
    size_t size = sizeof(*procInfo);
    return sysctl(cmd, sizeof(cmd) / sizeof(*cmd), procInfo, &size, NULL, 0) == 0;
}

+ (NSTimeInterval)processStartTime
{
    struct kinfo_proc kProcInfo;
    if ([self processInfoForPID:getpid() procInfo:&kProcInfo]) {
        return kProcInfo.kp_proc.p_un.__p_starttime.tv_sec + kProcInfo.kp_proc.p_un.__p_starttime.tv_usec / 1000000.0;
    } else {
        NSAssert(NO, @"无法取得进程的信息");
        return 0;
    }
}