coreutils

// nice.c, version 1.0.2

// OMKOV coreutils implementation of POSIX nice

// Copyright (C) 2020, Jakob Wakeling

// MIT Licence

#include "util/error.h"

#include "util/optget.h"

#include <unistd.h>

#include <errno.h>

#include <limits.h>

#include <stdbool.h>

#include <stdio.h>

#define VERSION "1.0.2"

static struct lop lops[] = {

	{ "help",    ARG_NUL, 256 },

	{ "version", ARG_NUL, 257 },

	{ NULL, 0, 0 }

};

static int n = 10;

static void hlp(void);

static void ver(void);

int main(int ac, char *av[]) { A0 = av[0];

	struct opt opt = OPTGET_INIT; opt.str = "n:"; opt.lops = lops;

	for (int o; (o = optget(&opt, av, 0)) != -1;) switch (o) {

	case 'n': {

		register char *s = opt.arg; register int c; bool neg = false;

		if (*s == '+') { ++s; } else if (*s == '-') { ++s; neg = true; }

		for (n = 0; *s >= '0' && *s <= '9'; ++s) { c = *s - '0';

			if (n > (INT_MAX - c) / 10) { break; } n = n * 10 + c;

		}

		if (*s) { error(1, "%s: invalid nice value", opt.arg); }

		if (neg) { n = -n; } break;

	}

	case 256: { hlp(); return 0; }

	case 257: { ver(); return 0; }

	default: { return 1; }

	}

	if (ac == 1) { printf("%d\n", nice(0)); return 0; }

	else if (opt.ind == ac) { error(1, "missing operand"); }

	errno = 0; nice(n); if (errno) { warn("%s", serr()); }

	execvp(av[opt.ind], &av[opt.ind]);

	warn("%s: %s", av[opt.ind], serr());

	return errno = ENOENT ? 127 : 126;

}

/* Print help information */

static void hlp(void) {

	puts("nice - invoke with an altered nice value\n");

	puts("usage: nice [-n increment] [command [argument...]]\n");

	puts("options:");

	puts("  -n increment  Nice increment value");

	puts("  --help        Display help information");

	puts("  --version     Display version information");

}

/* Print version information */

static void ver(void) {

	puts("OMKOV coreutils nice, version " VERSION);

	puts("Copyright (C) 2020, Jakob Wakeling");

	puts("MIT Licence (https://opensource.org/licenses/MIT)");

}