From c01641c89772a214c8b052a9e4b0f3a16b2f1e54 Mon Sep 17 00:00:00 2001
From: FRIGN <dev@frign.de>
Date: Mon, 2 Mar 2015 16:53:13 +0100
Subject: [PATCH] Audit nice(1)

1) val is sufficient as "int" (read the standard)
2) BUGFIX: If getpriority fails, it returns -1 and sets errno.
   Previously, it would correctly catch the errno but not take
   care of the fact that by then val has been decremented by 1.
   Only change val if the getpriority-call has been successful.
3) Add LIMIT()-macro from st to increase readability.
4) setpriority returns < 0 on failure
5) Remove bikeshedding-comment. Read the standard if you wonder.
6) return-value trick from env(1)
---
 README |  2 +-
 nice.1 |  4 ++--
 nice.c | 19 ++++++++++---------
 util.h |  2 ++
 4 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/README b/README
index 266dee3..cc19a7f 100644
--- a/README
+++ b/README
@@ -47,7 +47,7 @@ The following tools are implemented ('*' == finished, '#' == UTF-8 support,
 =*  mkfifo          yes                          none
 =*  mktemp          non-posix                    none
 =*  mv              yes                          none (-i)
-=*  nice            yes                          none
+=*| nice            yes                          none
 =   nl              no                           -d, -f, -h, -l, -p
 =*  nohup           yes                          none
 #*  paste           yes                          none
diff --git a/nice.1 b/nice.1
index a048f19..9c616a2 100644
--- a/nice.1
+++ b/nice.1
@@ -1,4 +1,4 @@
-.Dd January 28, 2015
+.Dd March 1, 2015
 .Dt NICE 1
 .Os sbase
 .Sh NAME
@@ -25,7 +25,7 @@ ranging from
 .Sy -20
 (highest priority)
 to
-.Sy +19
+.Sy +20
 (lowest priority).
 Default is 10.
 .El
diff --git a/nice.c b/nice.c
index 9f5b1a3..70a5c2d 100644
--- a/nice.c
+++ b/nice.c
@@ -16,8 +16,7 @@ usage(void)
 int
 main(int argc, char *argv[])
 {
-	long val = 10;
-	int savederrno;
+	int val = 10, r, savederrno;
 
 	ARGBEGIN {
 	case 'n':
@@ -28,20 +27,22 @@ main(int argc, char *argv[])
 		break;
 	} ARGEND;
 
-	if (argc == 0)
+	if (!argc)
 		usage();
 
 	errno = 0;
-	val += getpriority(PRIO_PROCESS, 0);
-	if (errno != 0)
+	r = getpriority(PRIO_PROCESS, 0);
+	if (errno)
 		weprintf("getpriority:");
-	val = MAX(PRIO_MIN, MIN(val, PRIO_MAX));
-	if (setpriority(PRIO_PROCESS, 0, val) != 0)
+	else
+		val += r;
+	LIMIT(val, PRIO_MIN, PRIO_MAX);
+	if (setpriority(PRIO_PROCESS, 0, val) < 0)
 		weprintf("setpriority:");
 
-	/* POSIX specifies the nice failure still invokes the command */
 	execvp(argv[0], argv);
 	savederrno = errno;
 	weprintf("execvp %s:", argv[0]);
-	return (savederrno == ENOENT)? 127 : 126;
+
+	return 126 + (savederrno == ENOENT);
 }
diff --git a/util.h b/util.h
index 4d89560..a107a07 100644
--- a/util.h
+++ b/util.h
@@ -13,6 +13,8 @@
 #define MIN(x,y)  ((x) < (y) ? (x) : (y))
 #undef MAX
 #define MAX(x,y)  ((x) > (y) ? (x) : (y))
+#undef LIMIT
+#define LIMIT(x, a, b)  (x) = (x) < (a) ? (a) : (x) > (b) ? (b) : (x)
 
 #define LEN(x) (sizeof (x) / sizeof *(x))