suggested addition to 'date'

At various times I've wanted to add timestamps to logfiles as they are 
generated..

usually this has involved perl or something to do it.

finally I broke down and just added  a small bit to date(1)

the -s option tells date to add a timestamp on the front of every line 
read in through stdin
and put it out through stdout.   teh format of the datestamp is governed 
exactly as usual so:

%ls | ./date -s +"%+: "
Fri Aug 11 19:53:34 PDT 2006: CVS
Fri Aug 11 19:53:34 PDT 2006: Makefile
Fri Aug 11 19:53:34 PDT 2006: date
Fri Aug 11 19:53:34 PDT 2006: date.1
Fri Aug 11 19:53:34 PDT 2006: date.1.gz
Fri Aug 11 19:53:34 PDT 2006: date.c
Fri Aug 11 19:53:34 PDT 2006: date.o
Fri Aug 11 19:53:34 PDT 2006: extern.h
Fri Aug 11 19:53:34 PDT 2006: netdate.c
Fri Aug 11 19:53:34 PDT 2006: netdate.o
Fri Aug 11 19:53:34 PDT 2006: vary.c
Fri Aug 11 19:53:34 PDT 2006: vary.h
Fri Aug 11 19:53:34 PDT 2006: vary.o
%ls | ./date -s +"%s: "
1155351474: CVS
1155351474: Makefile
1155351474: date
1155351474: date.1
1155351474: date.1.gz
1155351474: date.c
1155351474: date.o
1155351474: extern.h
1155351474: netdate.c
1155351474: netdate.o
1155351474: vary.c
1155351474: vary.h
1155351474: vary.o
%
I attach the diff.
I'm sure that someone who is a more competent practicioner of userland C 
programming
can probably clean this up abit.

do people think this is a worthwhile addition?

An easy to imagine use for this is to add it in the makefile for /usr so 
that "make buildworld" datestamped its output
(for example).

it makes it easy to timestamp output from a console logger for example:





? date
? date.1.gz
Index: date.c
===================================================================
RCS file: /usr/local/cvsroot/freebsd/src/bin/date/date.c,v
retrieving revision 1.47
diff -u -r1.47 date.c
--- date.c	10 Jan 2005 08:39:21 -0000	1.47
+++ date.c	12 Aug 2006 02:53:18 -0000
_at__at_ -74,7 +74,7 _at__at_
 {
 	struct timezone tz;
 	int ch, rflag;
-	int jflag, nflag;
+	int jflag, nflag, sflag;
 	const char *format;
 	char buf[1024];
 	char *endptr, *fmt;
_at__at_ -89,9 +89,9 _at__at_
 	(void) setlocale(LC_TIME, "");
 	tz.tz_dsttime = tz.tz_minuteswest = 0;
 	rflag = 0;
-	jflag = nflag = 0;
+	sflag = jflag = nflag = 0;
 	set_timezone = 0;
-	while ((ch = getopt(argc, argv, "d:f:jnr:t:uv:")) != -1)
+	while ((ch = getopt(argc, argv, "d:f:jnr:t:uv:s")) != -1)
 		switch((char)ch) {
 		case 'd':		/* daylight savings time */
 			tz.tz_dsttime = strtol(optarg, &endptr, 10) ? 1 : 0;
_at__at_ -114,6 +114,9 _at__at_
 			if (*tmp != 0)
 				usage();
 			break;
+		case 's':		/* don't set network */
+			sflag = 1;	/* stream mode */
+			break;
 		case 't':		/* minutes west of UTC */
 					/* error check; don't allow "PST" */
 			tz.tz_minuteswest = strtol(optarg, &endptr, 10);
_at__at_ -160,19 +163,47 _at__at_
 	if (*argv && **argv == '+')
 		format = *argv + 1;
 
-	lt = *localtime(&tval);
-	badv = vary_apply(v, &lt);
-	if (badv) {
-		fprintf(stderr, "%s: Cannot apply date adjustment\n",
-			badv->arg);
+	if (sflag) {
+		char linebuf[2048];
+		time_t otval = 0;
+		
+		while (fgets(linebuf, 2048, stdin)) {
+			if (!rflag && time(&tval) == -1)
+				err(1, "time");
+
+			if (tval != otval) {
+				lt = *localtime(&tval);
+				badv = vary_apply(v, &lt);
+				if (badv) {
+					fprintf(stderr, "%s: Cannot apply date adjustment\n",
+						badv->arg);
+					vary_destroy(v);
+					usage();
+				}
+				(void)strftime(buf, sizeof(buf), format, &lt);
+				otval = tval;
+			}
+			(void)printf("%s", buf);
+			fputs(linebuf, stdout);
+			if (fflush(stdout)) {
+				err(1, "stdout");
+			}
+		}
+	} else {
+		lt = *localtime(&tval);
+		badv = vary_apply(v, &lt);
+		if (badv) {
+			fprintf(stderr, "%s: Cannot apply date adjustment\n",
+				badv->arg);
+			vary_destroy(v);
+			usage();
+		}
 		vary_destroy(v);
-		usage();
+		(void)strftime(buf, sizeof(buf), format, &lt);
+		(void)printf("%s\n", buf);
+		if (fflush(stdout))
+			err(1, "stdout");
 	}
-	vary_destroy(v);
-	(void)strftime(buf, sizeof(buf), format, &lt);
-	(void)printf("%s\n", buf);
-	if (fflush(stdout))
-		err(1, "stdout");
 	exit(retval);
 }
 
_at__at_ -299,7 +330,7 _at__at_
 usage(void)
 {
 	(void)fprintf(stderr, "%s\n%s\n",
-	    "usage: date [-jnu] [-d dst] [-r seconds] [-t west] "
+	    "usage: date [-jnus] [-d dst] [-r seconds] [-t west] "
 	    "[-v[+|-]val[ymwdHMS]] ... ",
 	    "            "
 	    "[-f fmt date | [[[[[cc]yy]mm]dd]HH]MM[.ss]] [+format]");