Various fixes, add renice command.

This commit adds the renice command and its man page,
it also introduces some fixes:
* Makes nice command more solid, it also makes it respect POSIX return values.
* Fixes estrtol, which produced a misleading error on out of range errors.
* Fixes chgrp.1 NAME section.

Signed-off-by: Christoph Lohmann <20h@r-36.net>

Makefile

@@ -51,6 +51,7 @@ SRC = \
 	paste.c    \
 	printenv.c \
 	pwd.c      \
+	renice.c   \
 	rm.c       \
 	rmdir.c    \
 	sleep.c    \

chgrp.1

@@ -1,6 +1,6 @@
 .TH CHGRP 1 sbase\-VERSION
 .SH NAME
-nice \- invoke a utility with an altered nice value
+chgrp \- change the file group ownership
 .SH SYNOPSIS
 .B chgrp
 .RB [ \-R ]

nice.c

@@ -1,38 +1,44 @@
 /* See LICENSE file for copyright and license details. */
-#include <unistd.h>
+#include <errno.h>
+#include <limits.h>
 #include <stdio.h>
 #include <stdlib.h>
-#include <errno.h>
-#include <string.h>
+#include <unistd.h>
 #include "util.h"
 
-static void
-usage(void)
-{
-	eprintf("usage: nice [-n inc] command [options ...]\n");
-}
+static void eusage(void);
 
 int
 main(int argc, char **argv)
 {
-	int inc = 10;
+	long val = 10;
 
 	ARGBEGIN {
 	case 'n':
-		inc = atoi(EARGF(usage()));
+		val = estrtol(EARGF(eusage()), 10);
 		break;
 	default:
-		usage();
+		eusage();
+		break;
 	} ARGEND;
 
-	nice(inc); /* POSIX specifies the nice failure still invokes the command. */
+	if(argc == 0)
+		eusage();
 
-	if(!*argv)
-		usage();
+	errno = 0;
+	nice((int)MAX(INT_MIN, MIN(val, INT_MAX)));
+	if(errno != 0)
+		perror("can't adjust niceness");
 
-	execvp(*argv, argv);
-	eprintf("nice: '%s': %s\n", *argv, strerror(errno));
-
-	return EXIT_FAILURE;
+	/* POSIX specifies the nice failure still invokes the command */
+	execvp(argv[0], argv);
+	/* reached only on failure */
+	perror(argv[0]);
+	return (errno == ENOENT)? 127 : 126;
 }
 
+static void
+eusage(void)
+{
+	eprintf("usage: nice [-n inc] command [options ...]\n");
+}

renice.1

@@ -0,0 +1,97 @@
+.TH PASTE 1 renice-VERSION "Jun 2013"
+.SH NAME
+renice \- set nice values of running processes
+.SH "SYNOPSIS"
+.PP
+.B renice
+.B \-n
+.I increment
+[
+.B \-g
+|
+.B \-p
+|
+.B \-u
+]
+.I ID...
+.SH DESCRIPTION
+The
+.B renice
+utility requests that the nice values of one or more
+running processes be changed. By default, the applicable processes
+are specified by their process IDs. When a process group is specified
+(see 
+.B -g
+), the request applies to all processes in the process group. If the
+requested increment would raise or lower the nice value of the
+executed utility beyond its limits, then the limit whose value was
+exceeded is used. When a user is reniced, the request applies to all
+processes whose saved set-user-ID matches the user ID corresponding to
+the user. Regardless of which options are supplied or any other factor,
+renice does not alter the nice values of any process unless the user
+requesting such a change has appropriate privileges to do so for the
+specified process. If the user lacks appropriate privileges to perform
+the requested action, the utility returns an error status.
+The saved set-user-ID of the user's process is checked instead of its
+effective user ID when renice attempts to determine the user ID of the
+process in order to determine whether the user has appropriate privileges.
+.SH OPTIONS
+.TP
+.B \-g
+interpret all operands as unsigned decimal integer process group IDs.
+.TP
+.B \-n
+.I increment
+specify how the nice value of the specified process or processes
+is to be adjusted. The increment option-argument is a positive or
+negative decimal integer used to modify the nice value of the
+specified process or processes. positive increment values cause a
+lower nice value. Negative increment values may require appropriate
+privileges and cause a higher nice value.
+.TP
+.B \-p
+interpret all operands as unsigned decimal integer process IDs.
+The
+.B \-p
+option is the default if no options are specified.
+.TP
+.B \-u
+interpret all operands as users. If a user exists with a user name
+equal to the operand, then the user ID of that user is used in further
+processing. Otherwise, if the operand represents an unsigned decimal
+integer, used as the numeric user ID of the user.
+.SH EXIT VALUES
+On successful completion 0 is returned, a value which is >0 is
+returned on error.
+.SH FILES
+.TP
+.I /etc/passwd
+used to map user names to user ID's.
+.SH CONFORMING TO
+The
+.B renice
+utility is IEEE Std 1003.1-2001 (POSIX.1) compatible.
+.SH EXAMPLES
+.TP
+.I "renice -n 5 -p 987 32"
+.PP
+Adjust the nice value so that process IDs 987 and 32 would have a
+lower nice value.
+.TP
+.I "renice -n -4 -g 324 76"
+.PP
+Adjust the nice value so that group IDs 324 and 76 would have a
+higher nice value, if the user has the appropriate privileges to do so.
+.TP
+.I "renice -n 4 -u 8 sas"
+.PP
+Adjust the nice value so that numeric user ID 8 and user sas would
+have a lower nice value.
+Useful nice value increments on historical systems include
+19 or 20 (the affected processes run only when nothing else in the
+system attempts to run) and any negative number
+(to make processes run faster).
+.SH AUTHOR
+Written by Lorenzo Cogotti.
+.SH SEE ALSO
+.BR nice(1)

renice.c

@@ -0,0 +1,117 @@
+/* See LICENSE file for copyright and license details. */
+#include <errno.h>
+#include <limits.h>
+#include <pwd.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/resource.h>
+#include "util.h"
+
+static int strtop(const char *);
+static bool renice(int, int, long);
+static void eusage(void);
+
+int
+main(int argc, char **argv)
+{
+	const char *adj = NULL;
+	long val;
+	int i, which = PRIO_PROCESS, status = 0;
+
+	ARGBEGIN {
+	case 'n':
+		adj = EARGF(eusage());
+		break;
+	case 'g':
+		which = PRIO_PGRP;
+		break;
+	case 'p':
+		which = PRIO_PROCESS;
+		break;
+	case 'u':
+		which = PRIO_USER;
+		break;
+	default:
+		eusage();
+		break;
+	} ARGEND;
+
+	if(argc == 0 || !adj)
+		eusage();
+
+	val = estrtol(adj, 10);
+	for(i = 0; i < argc; i++) {
+		int who = -1;
+
+		if(which == PRIO_USER) {
+			const struct passwd *pwd;
+
+			errno = 0;
+			do pwd = getpwnam(argv[i]); while(errno == EINTR);
+
+			if(pwd)
+				who = pwd->pw_uid;
+			else if(errno != 0) {
+				perror("can't read passwd");
+				status = 1;
+				continue;
+			}
+		}
+		if(who < 0)
+			who = strtop(argv[i]);
+
+		if(who < 0 || !renice(which, who, val))
+			status = 1;
+	}
+
+	return status;
+}
+
+static int
+strtop(const char *s)
+{
+	char *end;
+	long n;
+
+	errno = 0;
+	n = strtol(s, &end, 10);
+	if(*end != '\0') {
+		fprintf(stderr, "%s: not an integer\n", s);
+		return -1;
+	}
+	if(errno != 0 || n <= 0 || n > INT_MAX) {
+		fprintf(stderr, "%s: invalid value\n", s);
+		return -1;
+	}
+
+	return (int)n;
+}
+
+static bool
+renice(int which, int who, long adj)
+{
+	errno = 0;
+	adj += getpriority(which, who);
+	if(errno != 0) {
+		fprintf(stderr, "can't get %d nice level: %s\n",
+		        who, strerror(errno));
+		return false;
+	}
+
+	adj = MAX(PRIO_MIN, MIN(adj, PRIO_MAX));
+	if(setpriority(which, who, (int)adj) == -1) {
+		fprintf(stderr, "can't set %d nice level: %s\n",
+		        who, strerror(errno));
+		return false;
+	}
+
+	return true;
+}
+
+static void
+eusage(void)
+{
+	eprintf("renice -n inc [-g | -p | -u] ID ...\n");
+}

util/estrtol.c

@@ -13,13 +13,14 @@ estrtol(const char *s, int base)
 
 	errno = 0;
 	n = strtol(s, &end, base);
-	if(*end != '\0' || errno != 0) {
-		if(base == 0) {
+	if(*end != '\0') {
+		if(base == 0)
 			eprintf("%s: not an integer\n", s);
-		} else {
+		else
 			eprintf("%s: not a base %d integer\n", s, base);
-		}
 	}
+	if(errno != 0)
+		eprintf("%s:", s);
 
 	return n;
 }