Linux uses C language to obtain the system startup duration

Linux uses C language to obtain the system startup duration

The idea is to obtain the system startup duration by reading/proc/uptime.
Run cat/proc/uptime

Man proc shows the following information:
Why? Http://www.bkjia.com/kf/ware/vc/ "target =" _ blank "class =" keylink "> placement/rj2ysfPtc2ztcS/1c/placement =" brush: java; ">#include #include #include #include struct timeval timeget(void){ struct timeval now; unsigned char timestr[60] = {0}; unsigned char uptimestr[30] = {0}; unsigned char * dotaddr; unsigned long second; char error = 0; FILE * timefile = NULL; timefile = fopen("/proc/uptime", "r"); if(!timefile) { printf("[%s:line:%d] error opening '/proc/uptime'",__FILE__,__LINE__); error = 1; goto out; } if( (fread(timestr, sizeof(char), 60, timefile)) == 0 ) { printf("[%s:line:%d] read '/proc/uptime' error",__FILE__,__LINE__); error = 1; goto out; } dotaddr = strchr(timestr, '.'); if((dotaddr - timestr + 2) < 30) memcpy(uptimestr, timestr, dotaddr - timestr + 2); else { printf("[%s:line:%d] uptime string is too long",__FILE__,__LINE__); error = 1; goto out; } uptimestr[dotaddr - timestr + 2] = '\0';out: if(error) { now.tv_sec = 0; now.tv_usec = 0; } else { now.tv_sec = atol(uptimestr); now.tv_usec = 0; } fclose(timefile); return now;}int main(){ struct timeval uptime; uptime = timeget(); printf("uptime = %lu\n", uptime.tv_sec); return 0;}

Running result: