utils-std

nice.c (1928B)

// utils-std: Collection of commonly available Unix tools
// SPDX-FileCopyrightText: 2017 Haelwenn (lanodan) Monnier <contact+utils@hacktivis.me>
// SPDX-License-Identifier: MPL-2.0
#define _POSIX_C_SOURCE 200809L
#define _XOPEN_SOURCE 700 // nice() is in XSI
#include <assert.h>
#include <errno.h>
#include <stdio.h>  // fprintf
#include <stdlib.h> // abort
#include <string.h> // strerror
#include <unistd.h> // getopt, nice
const char *argv0 = "nice";
static void
usage(void)
{
	fprintf(stderr, "Usage: nice [-n increment] command [argument ...]\n");
}
int
main(int argc, char *argv[])
{
	long incr = 0;
	int c = -1;
	while((c = getopt(argc, argv, ":n:")) != -1)
	{
		char *endptr = NULL;
		switch(c)
		{
		case 'n':
			incr = strtol(optarg, &endptr, 10);
			if(endptr && *endptr != 0) errno = EINVAL;
			if(errno != 0)
			{
				fprintf(stderr,
				        "%s: error: Failed parsing '%s' as a number: %s\n",
				        argv0,
				        optarg,
				        strerror(errno));
				usage();
				return 125;
			}
			break;
		case ':':
			fprintf(stderr, "%s: error: Missing operand for option: '-%c'\n", argv0, optopt);
			usage();
			return 125;
		case '?':
			fprintf(stderr, "%s: error: Unrecognised option: '-%c'\n", argv0, optopt);
			usage();
			return 125;
		default:
			abort();
		}
	}
	argc -= optind;
	argv += optind;
	if(argc == 0) return 0;
	errno = 0;
	if(nice((int)incr) == -1)
	{
		switch(errno)
		{
		case 0:
			break;
		case EPERM:
			fprintf(
			    stderr, "%s: warning: Failed setting nice to %ld: %s\n", argv0, incr, strerror(errno));
			errno = 0;
			break;
		default:
			fprintf(stderr, "%s: error: Failed setting nice to %ld: %s\n", argv0, incr, strerror(errno));
			return 125;
		}
	}
	assert(argv[0]);
	if(execvp(argv[0], argv) < 0)
	{
		fprintf(stderr, "%s: error: Failed executing '%s': %s\n", argv0, argv[0], strerror(errno));
		return (errno == ENOENT) ? 127 : 126;
	}
	abort();
}