utils

nproc.c (1080B)

// Collection of Unix tools, comparable to coreutils
// SPDX-FileCopyrightText: 2017-2022 Haelwenn (lanodan) Monnier <contact+utils@hacktivis.me>
// SPDX-License-Identifier: MPL-2.0
#define _DEFAULT_SOURCE // _SC_NPROCESSORS_CONF
#include <stdio.h>  // printf
#include <unistd.h> // sysconf, getopt, opt*
void
usage()
{
	fprintf(stderr, "Usage: nproc [-a]\n");
}
int
main(int argc, char *argv[])
{
	// _SC_NPROCESSORS_CONF &_SC_NPROCESSORS_ONLN aren't in POSIX yet but have been accepted
	// https://www.austingroupbugs.net/view.php?id=339
	int target = _SC_NPROCESSORS_ONLN;
	int c;
	while((c = getopt(argc, argv, ":a")) != EOF)
	{
		switch(c)
		{
		case 'a': // all processors
			target = _SC_NPROCESSORS_CONF;
			break;
		case ':':
			fprintf(stderr, "nproc: Error: Missing operand for option: '-%c'\n", optopt);
			usage();
			return 1;
		case '?':
			fprintf(stderr, "nproc: Error: Unrecognised option: '-%c'\n", optopt);
			usage();
			return 1;
		}
	}
	long np = sysconf(target);
	if(np < 0)
	{
		perror("sysconf");
		return 1;
	}
	printf("%ld\n", np);
	return 0;
}