Add 'nice' and replace 'renice' with a new implementation.

coreutils/nice.c

@@ -0,0 +1,86 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * nice implementation for busybox
+ *
+ * Copyright (C) 2005  Manuel Novoa III  <mjn3@codepoet.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <limits.h>
+#include <errno.h>
+#include <unistd.h>
+#include <sys/time.h>
+#include <sys/resource.h>
+#include "busybox.h"
+
+static inline int int_add_no_wrap(int a, int b)
+{
+	int s = a + b;
+
+	if (b < 0) {
+		if (s > a) s = INT_MIN;
+	} else {
+		if (s < a) s = INT_MAX;
+	}
+
+	return s;
+}
+
+int nice_main(int argc, char **argv)
+{
+	static const char Xetpriority_msg[] = "cannot %cet priority";
+
+	int old_priority, adjustment;
+
+	errno = 0;			 /* Needed for getpriority error detection. */
+	old_priority = getpriority(PRIO_PROCESS, 0);
+	if (errno) {
+		bb_perror_msg_and_die(Xetpriority_msg, 'g');
+	}
+
+	if (!*++argv) {	/* No args, so (GNU) output current nice value. */
+		bb_printf("%d\n", old_priority);
+		bb_fflush_stdout_and_exit(EXIT_SUCCESS);
+	}
+
+	adjustment = 10;			/* Set default adjustment. */
+
+	if ((argv[0][0] == '-') && (argv[0][1] == 'n') && !argv[0][2]) { /* "-n" */
+		if (argc < 4) {			/* Missing priority and/or utility! */
+			bb_show_usage();
+		}
+		adjustment = bb_xgetlarg(argv[1], 10, INT_MIN, INT_MAX);
+		argv += 2;
+	}
+
+	{  /* Set our priority.  Handle integer wrapping for old + adjust. */
+		int new_priority = int_add_no_wrap(old_priority, adjustment);
+
+		if (setpriority(PRIO_PROCESS, 0, new_priority) < 0) {
+			bb_perror_msg_and_die(Xetpriority_msg, 's');
+		}
+	}
+	
+	execvp(*argv, argv);		/* Now exec the desired program. */
+
+	/* The exec failed... */
+	bb_default_error_retval = (errno == ENOENT) ? 127 : 126; /* SUSv3 */
+	bb_perror_msg_and_die("%s", *argv);
+}