1 /* vi: set sw=4 ts=4: */
2 /*
3  * Factored out of mpstat/iostat.
4  *
5  * Copyright (C) 2010 Marek Polacek <mmpolacek@gmail.com>
6  *
7  * Licensed under GPLv2, see file LICENSE in this source tree.
8  */
9 #include "libbb.h"
10 
11 /* Does str start with "cpu"? */
starts_with_cpu(const char * str)12 int FAST_FUNC starts_with_cpu(const char *str)
13 {
14 	return ((str[0] - 'c') | (str[1] - 'p') | (str[2] - 'u')) == 0;
15 }
16 
17 /*
18  * Get number of processors. Uses /proc/stat.
19  * Return value 0 means one CPU and non SMP kernel.
20  * Otherwise N means N processor(s) and SMP kernel.
21  */
get_cpu_count(void)22 unsigned FAST_FUNC get_cpu_count(void)
23 {
24 	FILE *fp;
25 	char line[256];
26 	int proc_nr = -1;
27 
28 	fp = xfopen_for_read("/proc/stat");
29 	while (fgets(line, sizeof(line), fp)) {
30 		if (!starts_with_cpu(line)) {
31 			if (proc_nr >= 0)
32 				break; /* we are past "cpuN..." lines */
33 			continue;
34 		}
35 		if (line[3] != ' ') { /* "cpuN" */
36 			int num_proc;
37 			if (sscanf(line + 3, "%u", &num_proc) == 1
38 			 && num_proc > proc_nr
39 			) {
40 				proc_nr = num_proc;
41 			}
42 		}
43 	}
44 
45 	fclose(fp);
46 	return proc_nr + 1;
47 }
48