struct sysinfo {  long uptime;             /* Seconds since boot */  unsigned long loads[3];  /* 1, 5, and 15 minute load averages */  unsigned long totalram;  /* Total usable main memory size */  unsigned long freeram;   /* Available memory size */  unsigned long sharedram; /* Amount of shared memory */  unsigned long bufferram; /* Memory used by buffers */  unsigned long totalswap; /* Total swap space size */  unsigned long freeswap;  /* swap space still available */  unsigned short procs;    /* Number of current processes */  char _f[22];             /* Pads structure to 64 bytes */ };

#include <stdio.h> #include <sys/sysinfo.h> #include <time.h> #include <errno.h> static int print_system_boot_time() {     struct sysinfo info;     time_t cur_time = 0;     time_t boot_time = 0;     struct tm *ptm = NULL;     if (sysinfo(&info)) {     fprintf(stderr, "Failed to get sysinfo, errno:%u, reason:%s\n",         errno, strerror(errno));     return -1;     }     time(&cur_time);     if (cur_time > info.uptime) {     boot_time = cur_time - info.uptime;     }     else {     boot_time = info.uptime - cur_time;     }     ptm = gmtime(&boot_time);     printf("System boot time: %d-%-d-%d %d:%d:%d\n", ptm->tm_year + 1900,         ptm->tm_mon + 1, ptm->tm_mday, ptm->tm_hour, ptm->tm_min, ptm->tm_sec);    return 0; } int main() {     if (print_system_boot_time() != 0) {     return -1;     }     return 0; }