2 files changed, 32 insertions, 5 deletions
diff --git a/lib/libc/gen/nice.3 b/lib/libc/gen/nice.3
index 9c39b78..3bad5f7 100644
--- a/lib/libc/gen/nice.3
+++ b/lib/libc/gen/nice.3
@@ -28,7 +28,7 @@
 .\"     @(#)nice.3	8.1 (Berkeley) 6/4/93
 .\" $FreeBSD$
 .\"
-.Dd June 4, 1993
+.Dd February 22, 2015
 .Dt NICE 3
 .Os
 .Sh NAME
@@ -57,11 +57,34 @@ Only the super-user may lower priorities.
 .Pp
 Children inherit the priority of their parent processes via
 .Xr fork 2 .
+.Sh RETURN VALUES
+Upon successful completion,
+.Fn nice
+returns the new nice value minus
+.Dv NZERO .
+Otherwise, \-1 is returned, the process' nice value is not changed, and
+.Va errno
+is set to indicate the error.
+.Sh ERRORS
+The
+.Fn nice
+function will fail if:
+.Bl -tag -width Er
+.It Bq Er EPERM
+The
+.Fa incr
+argument is negative and the caller does not have appropriate privileges.
+.El
 .Sh SEE ALSO
 .Xr nice 1 ,
 .Xr fork 2 ,
 .Xr setpriority 2 ,
 .Xr renice 8
+.Sh STANDARDS
+The
+.Fn nice
+function conforms to
+.St -xpg4.2 .
 .Sh HISTORY
 A
 .Fn nice
diff --git a/lib/libc/gen/nice.c b/lib/libc/gen/nice.c
index e8375e8..58cde98 100644
--- a/lib/libc/gen/nice.c
+++ b/lib/libc/gen/nice.c
@@ -43,14 +43,18 @@ __FBSDID("$FreeBSD$");
  * Backwards compatible nice.
  */
 int
-nice(incr)
-	int incr;
+nice(int incr)
 {
 	int prio;
 
 	errno = 0;
 	prio = getpriority(PRIO_PROCESS, 0);
 	if (prio == -1 && errno)
-		return (-1);
-	return (setpriority(PRIO_PROCESS, 0, prio + incr));
+		return -1;
+	if (setpriority(PRIO_PROCESS, 0, prio + incr) == -1) {
+		if (errno == EACCES)
+			errno = EPERM;
+		return -1;
+	}
+	return getpriority(PRIO_PROCESS, 0);
 }