nproc: new applet

function                                             old     new   delta
nproc_main                                             -      98     +98
applet_names                                        2584    2590      +6
applet_main                                         1496    1500      +4
applet_install_loc                                   187     188      +1

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

coreutils/nproc.c

@@ -0,0 +1,51 @@
+/*
+ * Copyright (C) 2017 Denys Vlasenko <vda.linux@googlemail.com>
+ *
+ * Licensed under GPLv2, see LICENSE in this source tree
+ */
+//config:config NPROC
+//config:	bool "nproc"
+//config:	default y
+//config:	help
+//config:	  Print number of CPUs
+
+//applet:IF_NPROC(APPLET(nproc, BB_DIR_USR_BIN, BB_SUID_DROP))
+
+//kbuild:lib-$(CONFIG_NPROC) += nproc.o
+
+//usage:#define nproc_trivial_usage
+//usage:	""
+//TODO: "[--all] [--ignore=N]"
+//usage:#define nproc_full_usage "\n\n"
+//usage:	"Print number of CPUs"
+
+#include <sched.h>
+#include "libbb.h"
+
+int nproc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int nproc_main(int argc UNUSED_PARAM, char **argv UNUSED_PARAM)
+{
+	unsigned long mask[1024];
+	unsigned i, count = 0;
+
+	//applet_long_options = ...;
+	//getopt32(argv, "");
+
+	//if --all, count /sys/devices/system/cpu/cpuN dirs, else:
+
+	if (sched_getaffinity(0, sizeof(mask), (void*)mask) == 0) {
+		for (i = 0; i < ARRAY_SIZE(mask); i++) {
+			unsigned long m = mask[i];
+			while (m) {
+				if (m & 1)
+					count++;
+				m >>= 1;
+			}
+		}
+	}
+	if (count == 0)
+		count++;
+	printf("%u\n", count);
+
+	return 0;
+}