1 files changed, 132 insertions, 0 deletions
diff --git a/bin/nproc/nproc.c b/bin/nproc/nproc.c
new file mode 100644
index 000000000000..d8affe11b796
--- /dev/null
+++ b/bin/nproc/nproc.c
@@ -0,0 +1,132 @@
+/*-
+ * Copyright (c) 2023 Mateusz Guzik
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+/*
+ * This program is intended to be compatible with nproc as found in GNU
+ * coreutils.
+ *
+ * In order to maintain that, do not add any features here if they are not
+ * present in said program.  If you are looking for anything more advanced you
+ * probably should patch cpuset(1) instead.
+ */
+
+#include <sys/param.h>
+#include <sys/cpuset.h>
+
+#include <err.h>
+#include <errno.h>
+#include <getopt.h>
+#include <limits.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sysexits.h>
+#include <unistd.h>
+
+#define OPT_ALL		(CHAR_MAX + 1)
+#define OPT_IGNORE	(CHAR_MAX + 2)
+#define OPT_VERSION	(CHAR_MAX + 3)
+#define OPT_HELP	(CHAR_MAX + 4)
+
+static struct option long_opts[] = {
+	{ "all", no_argument, NULL, OPT_ALL },
+	{ "ignore", required_argument, NULL, OPT_IGNORE },
+	{ "version", no_argument, NULL, OPT_VERSION },
+	{ "help", no_argument, NULL, OPT_HELP },
+	{ NULL, 0, NULL, 0 }
+};
+
+static void
+help(void)
+{
+	fprintf(stderr,
+    "usage: nproc [--all] [--ignore=count]\n");
+	fprintf(stderr,
+    "       nproc --help\n");
+	fprintf(stderr,
+    "       nproc --version\n");
+}
+
+static void
+usage(void)
+{
+	help();
+	exit(EX_USAGE);
+}
+
+/*
+ * GNU variant ships with the --version switch.
+ *
+ * While we don't have anything to put there, print something which is
+ * whitespace-compatible with the original. Version number was taken
+ * from coreutils this code is in sync with.
+ */
+static void
+version(void)
+{
+	printf("nproc (neither_GNU nor_coreutils) 8.32\n");
+	exit(EXIT_SUCCESS);
+}
+
+int
+main(int argc, char *argv[])
+{
+	const char *errstr;
+	cpuset_t mask;
+	int ch, cpus, ignore;
+	bool all_flag;
+
+	ignore = 0;
+	all_flag = false;
+
+	while ((ch = getopt_long(argc, argv, "", long_opts, NULL)) != -1) {
+		switch (ch) {
+		case OPT_ALL:
+			all_flag = true;
+			break;
+		case OPT_IGNORE:
+			ignore = strtonum(optarg, 0, INT_MAX, &errstr);
+			if (errstr)
+				errx(1, "bad ignore count: %s", errstr);
+			break;
+		case OPT_VERSION:
+			version();
+			__unreachable();
+		case OPT_HELP:
+			help();
+			exit(EXIT_SUCCESS);
+		default:
+			usage();
+		}
+	}
+
+	argc -= optind;
+	argv += optind;
+
+	if (argc != 0)
+		usage();
+
+	if (all_flag) {
+		cpus = sysconf(_SC_NPROCESSORS_CONF);
+		if (cpus == -1)
+			err(1, "sysconf");
+	} else {
+		CPU_ZERO(&mask);
+		if (cpuset_getaffinity(CPU_LEVEL_WHICH, CPU_WHICH_TID, -1,
+		    sizeof(mask), &mask) != 0)
+			err(1, "cpuset_getaffinity");
+		cpus = CPU_COUNT(&mask);
+	}
+
+	if (ignore >= cpus)
+		cpus = 1;
+	else
+		cpus -= ignore;
+
+	printf("%u\n", cpus);
+
+	exit(EXIT_SUCCESS);
+}