Implement POSIX -n option, cleanup an arguments parsing a bit.

PR:		bin/34076, bin/35929
Reviewed by:	bde
Obtained from:	NetBSD
MFC after:	1 week

usr.bin/renice/renice.8

@@ -40,7 +40,10 @@
 .Nd alter priority of running processes
 .Sh SYNOPSIS
 .Nm
-.Ar priority
+.Oo
+.Ar priority |
+.Op Fl n Ar increment
+.Oc
 .Oo
 .Op Fl p
 .Ar pid ...
@@ -77,6 +80,10 @@ Options supported by
 Force
 .Ar who
 parameters to be interpreted as process group ID's.
+.It Fl n
+Instead of changing the specified processes to the given priority,
+interpret the following argument as an increment to be applied to
+the current priority of each process.
 .It Fl u
 Force the
 .Ar who

usr.bin/renice/renice.c

@@ -51,12 +51,14 @@ static const char rcsid[] =
 
 #include <err.h>
 #include <errno.h>
+#include <limits.h>
 #include <pwd.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
-static int	donice(int, int, int);
+static int	donice(int, int, int, int);
+static int	getnum(const char *, const char *, int *);
 static void	usage(void);
 
 /*
@@ -68,14 +70,23 @@ int
 main(int argc, char *argv[])
 {
 	struct passwd *pwd;
-	int errs, prio, which, who;
+	int errs, incr, prio, which, who;
 
 	errs = 0;
+	incr = 0;
 	which = PRIO_PROCESS;
 	who = 0;
 	argc--, argv++;
 	if (argc < 2)
 		usage();
+	if (strcmp(*argv, "-n") == 0) {
+		incr = 1;
+		argc--, argv++;
+		if (argc == 0)
+			usage();
+	}
+	if (getnum("priority", *argv, &prio))
+		return (1);
 	prio = atoi(*argv);
 	argc--, argv++;
 	if (prio > PRIO_MAX)
@@ -103,19 +114,20 @@ main(int argc, char *argv[])
 			}
 			who = pwd->pw_uid;
 		} else {
-			who = atoi(*argv);
+			if (getnum("pid", *argv, &who))
+				continue;
 			if (who < 0) {
 				warnx("%s: bad value", *argv);
 				continue;
 			}
 		}
-		errs += donice(which, who, prio);
+		errs += donice(which, who, prio, incr);
 	}
 	exit(errs != 0);
 }
 
 static int
-donice(int which, int who, int prio)
+donice(int which, int who, int prio, int incr)
 {
 	int oldprio;
 
@@ -125,6 +137,12 @@ donice(int which, int who, int prio)
 		warn("%d: getpriority", who);
 		return (1);
 	}
+	if (incr)
+		prio = oldprio + prio;
+	if (prio > PRIO_MAX)
+		prio = PRIO_MAX;
+	if (prio < PRIO_MIN)
+		prio = PRIO_MIN;
 	if (setpriority(which, who, prio) < 0) {
 		warn("%d: setpriority", who);
 		return (1);
@@ -133,10 +151,32 @@ donice(int which, int who, int prio)
 	return (0);
 }
 
+static int
+getnum(const char *com, const char *str, int *val)
+{
+	long v;
+	char *ep;
+
+	errno = 0;
+	v = strtol(str, &ep, NULL);
+	if (v < INT_MIN || v > INT_MAX || errno == ERANGE) {
+		warnx("%s argument %s is out of range.", com, str);
+		return (1);
+	}
+	if (ep == str || *ep != '\0' || errno != 0) {
+		warnx("Bad %s argument: %s.", com, str);
+		return (1);
+	}
+
+	*val = (int)v;
+	return (0);
+}
+
 static void
 usage()
 {
-	fprintf(stderr,
-"usage: renice priority [ [ -p ] pids ] [ [ -g ] pgrps ] [ [ -u ] users ]\n");
+	fprintf(stderr, "%s\n%s\n",
+"usage: renice [priority | [-n incr]] [ [ -p ] pids ] [ [ -g ] pgrps ]",
+"              [ [ -u ] users ]");
 	exit(1);
 }