1 /* 2 * Copyright (c) 1983, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)nice.c 8.1 (Berkeley) 6/4/93 30 * $DragonFly: src/lib/libc/gen/nice.c,v 1.3 2005/11/13 00:07:42 swildner Exp $ 31 */ 32 33 #include <sys/types.h> 34 #include <sys/time.h> 35 #include <sys/resource.h> 36 #include <errno.h> 37 #include <unistd.h> 38 39 /* 40 * Backwards compatible nice. 41 */ 42 int 43 nice(int incr) 44 { 45 int prio; 46 47 /* 48 * If we aren't privileged enough to lower our nice value we shall 49 * return EPERM, contrary to setpriority() which is required to return 50 * EACCES. 51 */ 52 if (incr < 0 && (geteuid() != 0)) { 53 errno = EPERM; 54 return (-1); 55 } 56 57 /* 58 * -1 is a permissible value in a successful scenario. That's why we 59 * zero out errno and check against it afterwards, to differentiate 60 * between a legitimate value and a failure. 61 */ 62 errno = 0; 63 prio = getpriority(PRIO_PROCESS, 0); 64 if (prio == -1 && errno) 65 return (-1); 66 67 if (setpriority(PRIO_PROCESS, 0, prio + incr) == -1) 68 return (-1); 69 return (getpriority(PRIO_PROCESS, 0)); 70 } 71