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glibc  2.9
nice.c
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00001 /* Copyright (C) 1992, 1996, 1997, 2001, 2002, 2006
00002    Free Software Foundation, Inc.
00003    This file is part of the GNU C Library.
00004 
00005    The GNU C Library is free software; you can redistribute it and/or
00006    modify it under the terms of the GNU Lesser General Public
00007    License as published by the Free Software Foundation; either
00008    version 2.1 of the License, or (at your option) any later version.
00009 
00010    The GNU C Library is distributed in the hope that it will be useful,
00011    but WITHOUT ANY WARRANTY; without even the implied warranty of
00012    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00013    Lesser General Public License for more details.
00014 
00015    You should have received a copy of the GNU Lesser General Public
00016    License along with the GNU C Library; if not, write to the Free
00017    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00018    02111-1307 USA.  */
00019 
00020 #include <errno.h>
00021 #include <unistd.h>
00022 #include <sys/resource.h>
00023 
00024 /* Increment the scheduling priority of the calling process by INCR.
00025    The superuser may use a negative INCR to decrement the priority.  */
00026 int
00027 nice (int incr)
00028 {
00029   int save;
00030   int prio;
00031   int result;
00032 
00033   /* -1 is a valid priority, so we use errno to check for an error.  */
00034   save = errno;
00035   __set_errno (0);
00036   prio = getpriority (PRIO_PROCESS, 0);
00037   if (prio == -1)
00038     {
00039       if (errno != 0)
00040        return -1;
00041       else
00042        __set_errno (save);
00043     }
00044 
00045   result = setpriority (PRIO_PROCESS, 0, prio + incr);
00046   if (result == -1)
00047     {
00048       if (errno == EACCES)
00049        errno = EPERM;
00050       return -1;
00051     }
00052   return getpriority (PRIO_PROCESS, 0);
00053 }