Add '-P' option which allows to specify pidfile.

usr.sbin/powerd/Makefile

@@ -4,4 +4,7 @@ PROG=	powerd
 MAN=	powerd.8
 WARNS?=	6
 
+DPADD=	${LIBUTIL}
+LDADD=	-lutil
+
 .include <bsd.prog.mk>

usr.sbin/powerd/powerd.8

@@ -37,6 +37,7 @@
 .Op Fl i Ar percent
 .Op Fl n Ar mode
 .Op Fl p Ar ival
+.Op Fl P Ar pidfile
 .Op Fl r Ar percent
 .Op Fl v
 .Sh DESCRIPTION
@@ -82,6 +83,10 @@ to use normally when the AC line state is unknown.
 Specifies a different polling interval (in milliseconds) for AC line state
 and system idle levels.
 The default is 500 ms.
+.It Fl P
+Specify an alternative file in which to store the process ID.
+The default is
+.Pa /var/run/powerd.pid .
 .It Fl r Ar percent
 Specifies the CPU idle percent level where
 adaptive

usr.sbin/powerd/powerd.c

@@ -28,9 +28,15 @@
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
+#include <sys/param.h>
+#include <sys/ioctl.h>
+#include <sys/sysctl.h>
+#include <sys/resource.h>
+
 #include <err.h>
 #include <errno.h>
 #include <fcntl.h>
+#include <libutil.h>
 #include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -41,10 +47,6 @@ __FBSDID("$FreeBSD$");
 #include <machine/apm_bios.h>
 #endif
 
-#include <sys/ioctl.h>
-#include <sys/sysctl.h>
-#include <sys/resource.h>
-
 #define DEFAULT_ACTIVE_PERCENT	65
 #define DEFAULT_IDLE_PERCENT	90
 #define DEFAULT_POLL_INTERVAL	500	/* Poll interval in milliseconds */
@@ -247,13 +249,15 @@ usage(void)
 {
 
 	fprintf(stderr,
-"usage: powerd [-v] [-a mode] [-b mode] [-i %%] [-n mode] [-p ival] [-r %%]\n");
+"usage: powerd [-v] [-a mode] [-b mode] [-i %%] [-n mode] [-p ival] [-r %%] [-P pidfile]\n");
 	exit(1);
 }
 
 int
 main(int argc, char * argv[])
 {
+	struct pidfh *pfh;
+	const char *pidfile = NULL;
 	long idle, total;
 	int curfreq, *freqs, i, *mwatts, numfreqs;
 	int ch, mode_ac, mode_battery, mode_none, acline, mode, vflag;
@@ -273,7 +277,7 @@ main(int argc, char * argv[])
 	if (geteuid() != 0)
 		errx(1, "must be root to run");
 
-	while ((ch = getopt(argc, argv, "a:b:i:n:p:r:v")) != EOF)
+	while ((ch = getopt(argc, argv, "a:b:i:n:p:P:r:v")) != EOF)
 		switch (ch) {
 		case 'a':
 			parse_mode(optarg, &mode_ac, ch);
@@ -299,6 +303,9 @@ main(int argc, char * argv[])
 				usage();
 			}
 			break;
+		case 'P':
+			pidfile = optarg;
+			break;
 		case 'r':
 			cpu_running_mark = atoi(optarg);
 			if (cpu_running_mark < 0 || cpu_running_mark > 100) {
@@ -338,8 +345,20 @@ main(int argc, char * argv[])
 	acline_init();
 
 	/* Run in the background unless in verbose mode. */
-	if (!vflag)
+	if (!vflag) {
+		pid_t otherpid;
+
+		pfh = pidfile_open(pidfile, 0600, &otherpid);
+		if (pfh == NULL) {
+			if (errno == EEXIST) {
+				errx(1, "powerd already running, pid: %d",
+				    otherpid);
+			}
+			warn("cannot open pid file");
+		}
 		daemon(0, 0);
+		pidfile_write(pfh);
+	}
 	signal(SIGINT, handle_sigs);
 	signal(SIGTERM, handle_sigs);
 
@@ -460,6 +479,8 @@ main(int argc, char * argv[])
 	}
 	free(freqs);
 	free(mwatts);
+	if (!vflag)
+		pidfile_remove(pfh);
 
 	exit(0);
 }