date: Add support for nanoseconds

This patch introduces support for a conversion specification for
nanoseconds.

The format of %N is meant to be compatible with that of GNU date.

The nanoseconds conversion specification is implemented directly in
date(1) instead of libc (in strftime(3)) to avoid introducing
non-standard functions to libc at this time and modifying struct tm.

Apart from introducing the nanoseconds conversion specification, this
patch brings the following changes:

- The "ns" format for ISO 8061 dates is now unlocked. E.g., date -Ins
  prints:
      2024-04-22T12:20:28,763742224+02:00
- The -r flag when fed a file is now aware of the nanosecond part of the last
  modification time.
- date(1) is now able to set the time with nanosecond precision. It is
  not possible as of now to do that by specifying nanoseconds directly
  via the command-line arguments. Instead, the -r flag can be used.
- date(1) is now using the clock_gettime(3) family of functions instead
  of ctime(3) family of functions where possible.

Reviewed by:	des, markj
Sponsored by:	Klara, Inc.
Differential Revision:	https://reviews.freebsd.org/D44905

3 files changed, 142 insertions, 35 deletions

diff --git a/bin/date/date.1 b/bin/date/date.1
index 286b1f45414a..afa6d555a503 100644
--- a/bin/date/date.1
+++ b/bin/date/date.1
@@ -29,7 +29,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd May 19, 2023
+.Dd April 26, 2024
 .Dt DATE 1
 .Os
 .Sh NAME
@@ -141,17 +141,19 @@ values are
 .Cm date ,
 .Cm hours ,
 .Cm minutes ,
+.Cm seconds ,
 and
-.Cm seconds .
+.Cm ns No Pq for nanoseconds .
 The date and time is formatted to the specified precision.
 When
 .Ar FMT
 is
 .Cm hours
-(or the more precise
-.Cm minutes
+.Po or the more precise
+.Cm minutes ,
+.Cm seconds ,
 or
-.Cm seconds ) ,
+.Cm ns Pc ,
 the
 .St -iso8601
 format includes the timezone.
@@ -325,7 +327,9 @@ which specifies the format in which to display the date and time.
 The format string may contain any of the conversion specifications
 described in the
 .Xr strftime 3
-manual page, as well as any arbitrary text.
+manual page and
+.Ql %N
+for nanoseconds, as well as any arbitrary text.
 A newline
 .Pq Ql \en
 character is always output after the characters specified by
@@ -551,6 +555,7 @@ prints:
 and exits with status 1.
 .Sh SEE ALSO
 .Xr locale 1 ,
+.Xr clock_gettime 2 ,
 .Xr gettimeofday 2 ,
 .Xr getutxent 3 ,
 .Xr strftime 3 ,
@@ -581,6 +586,12 @@ The format selected by the
 .Fl I
 flag is compatible with
 .St -iso8601 .
+.Pp
+The
+.Ql %N
+conversion specification for nanoseconds is a non-standard extension.
+It is compatible with GNU date's
+.Ql %N .
 .Sh HISTORY
 A
 .Nm
@@ -599,3 +610,8 @@ The
 .Fl I
 flag was added in
 .Fx 12.0 .
+.Pp
+The
+.Ql %N
+conversion specification was added in
+.Fx 15.0 .
diff --git a/bin/date/date.c b/bin/date/date.c
index 0ff3b9f74cbd..ccd72cb98445 100644
--- a/bin/date/date.c
+++ b/bin/date/date.c
@@ -35,6 +35,7 @@
 
 #include <ctype.h>
 #include <err.h>
+#include <errno.h>
 #include <locale.h>
 #include <stdbool.h>
 #include <stdio.h>
@@ -50,14 +51,14 @@
 #define	TM_YEAR_BASE	1900
 #endif
 
-static time_t tval;
-
 static void badformat(void);
 static void iso8601_usage(const char *) __dead2;
 static void multipleformats(void);
 static void printdate(const char *);
-static void printisodate(struct tm *);
-static void setthetime(const char *, const char *, int);
+static void printisodate(struct tm *, long);
+static void setthetime(const char *, const char *, int, struct timespec *);
+static size_t strftime_ns(char * __restrict, size_t, const char * __restrict,
+    const struct tm * __restrict, long);
 static void usage(void) __dead2;
 
 static const struct iso8601_fmt {
@@ -68,6 +69,7 @@ static const struct iso8601_fmt {
 	{ "hours", "T%H" },
 	{ "minutes", ":%M" },
 	{ "seconds", ":%S" },
+	{ "ns", ",%N" },
 };
 static const struct iso8601_fmt *iso8601_selected;
 
@@ -76,6 +78,7 @@ static const char *rfc2822_format = "%a, %d %b %Y %T %z";
 int
 main(int argc, char *argv[])
 {
+	struct timespec ts;
 	int ch, rflag;
 	bool Iflag, jflag, Rflag;
 	const char *format;
@@ -126,11 +129,12 @@ main(int argc, char *argv[])
 			break;
 		case 'r':		/* user specified seconds */
 			rflag = 1;
-			tval = strtoq(optarg, &tmp, 0);
+			ts.tv_sec = strtoq(optarg, &tmp, 0);
 			if (*tmp != 0) {
-				if (stat(optarg, &sb) == 0)
-					tval = sb.st_mtim.tv_sec;
-				else
+				if (stat(optarg, &sb) == 0) {
+					ts.tv_sec = sb.st_mtim.tv_sec;
+					ts.tv_nsec = sb.st_mtim.tv_nsec;
+				} else
 					usage();
 			}
 			break;
@@ -149,8 +153,8 @@ main(int argc, char *argv[])
 	argc -= optind;
 	argv += optind;
 
-	if (!rflag && time(&tval) == -1)
-		err(1, "time");
+	if (!rflag && clock_gettime(CLOCK_REALTIME, &ts) == -1)
+		err(1, "clock_gettime");
 
 	format = "%+";
 
@@ -166,7 +170,7 @@ main(int argc, char *argv[])
 	}
 
 	if (*argv) {
-		setthetime(fmt, *argv, jflag);
+		setthetime(fmt, *argv, jflag, &ts);
 		++argv;
 	} else if (fmt != NULL)
 		usage();
@@ -179,7 +183,7 @@ main(int argc, char *argv[])
 
 	if (outzone != NULL && setenv("TZ", outzone, 1) != 0)
 		err(1, "setenv(TZ)");
-	lt = localtime(&tval);
+	lt = localtime(&ts.tv_sec);
 	if (lt == NULL)
 		errx(1, "invalid time");
 	badv = vary_apply(v, lt);
@@ -192,7 +196,7 @@ main(int argc, char *argv[])
 	vary_destroy(v);
 
 	if (Iflag)
-		printisodate(lt);
+		printisodate(lt, ts.tv_nsec);
 
 	if (format == rfc2822_format)
 		/*
@@ -202,7 +206,7 @@ main(int argc, char *argv[])
 		setlocale(LC_TIME, "C");
 
 
-	(void)strftime(buf, sizeof(buf), format, lt);
+	(void)strftime_ns(buf, sizeof(buf), format, lt, ts.tv_nsec);
 	printdate(buf);
 }
 
@@ -216,19 +220,19 @@ printdate(const char *buf)
 }
 
 static void
-printisodate(struct tm *lt)
+printisodate(struct tm *lt, long nsec)
 {
 	const struct iso8601_fmt *it;
-	char fmtbuf[32], buf[32], tzbuf[8];
+	char fmtbuf[64], buf[64], tzbuf[8];
 
 	fmtbuf[0] = 0;
 	for (it = iso8601_fmts; it <= iso8601_selected; it++)
 		strlcat(fmtbuf, it->format_string, sizeof(fmtbuf));
 
-	(void)strftime(buf, sizeof(buf), fmtbuf, lt);
+	(void)strftime_ns(buf, sizeof(buf), fmtbuf, lt, nsec);
 
 	if (iso8601_selected > iso8601_fmts) {
-		(void)strftime(tzbuf, sizeof(tzbuf), "%z", lt);
+		(void)strftime_ns(tzbuf, sizeof(tzbuf), "%z", lt, nsec);
 		memmove(&tzbuf[4], &tzbuf[3], 3);
 		tzbuf[3] = ':';
 		strlcat(buf, tzbuf, sizeof(buf));
@@ -240,15 +244,14 @@ printisodate(struct tm *lt)
 #define	ATOI2(s)	((s) += 2, ((s)[-2] - '0') * 10 + ((s)[-1] - '0'))
 
 static void
-setthetime(const char *fmt, const char *p, int jflag)
+setthetime(const char *fmt, const char *p, int jflag, struct timespec *ts)
 {
 	struct utmpx utx;
 	struct tm *lt;
-	struct timeval tv;
 	const char *dot, *t;
 	int century;
 
-	lt = localtime(&tval);
+	lt = localtime(&ts->tv_sec);
 	if (lt == NULL)
 		errx(1, "invalid time");
 	lt->tm_isdst = -1;		/* divine correct DST */
@@ -329,18 +332,17 @@ setthetime(const char *fmt, const char *p, int jflag)
 	}
 
 	/* convert broken-down time to GMT clock time */
-	if ((tval = mktime(lt)) == -1)
+	if ((ts->tv_sec = mktime(lt)) == -1)
 		errx(1, "nonexistent time");
+	ts->tv_nsec = 0;
 
 	if (!jflag) {
 		utx.ut_type = OLD_TIME;
 		memset(utx.ut_id, 0, sizeof(utx.ut_id));
 		(void)gettimeofday(&utx.ut_tv, NULL);
 		pututxline(&utx);
-		tv.tv_sec = tval;
-		tv.tv_usec = 0;
-		if (settimeofday(&tv, NULL) != 0)
-			err(1, "settimeofday (timeval)");
+		if (clock_settime(CLOCK_REALTIME, ts) != 0)
+			err(1, "clock_settime");
 		utx.ut_type = NEW_TIME;
 		(void)gettimeofday(&utx.ut_tv, NULL);
 		pututxline(&utx);
@@ -351,6 +353,82 @@ setthetime(const char *fmt, const char *p, int jflag)
 	}
 }
 
+/*
+ * The strftime_ns function is a wrapper around strftime(3), which adds support
+ * for features absent from strftime(3). Currently, the only extra feature is
+ * support for %N, the nanosecond conversion specification.
+ *
+ * The functions scans the format string for the non-standard conversion
+ * specifications and replaces them with the date and time values before
+ * passing the format string to strftime(3). The handling of the non-standard
+ * conversion specifications happens before the call to strftime(3) to handle
+ * cases like "%%N" correctly ("%%N" should yield "%N" instead of nanoseconds).
+ */
+static size_t
+strftime_ns(char * __restrict s, size_t maxsize, const char * __restrict format,
+    const struct tm * __restrict t, long nsec)
+{
+	size_t prefixlen;
+	size_t ret;
+	char *newformat;
+	char *oldformat;
+	const char *prefix;
+	const char *suffix;
+	const char *tok;
+	bool seen_percent;
+
+	seen_percent = false;
+	if (asprintf(&newformat, "%s", format) < 0)
+		err(1, "asprintf");
+	tok = newformat;
+	for (tok = newformat; *tok != '\0'; tok++) {
+		switch (*tok) {
+		case '%':
+			/*
+			 * If the previous token was a percent sign,
+			 * then there are two percent tokens in a row.
+			 */
+			if (seen_percent)
+				seen_percent = false;
+			else
+				seen_percent = true;
+			break;
+		case 'N':
+			if (seen_percent) {
+				oldformat = newformat;
+				prefix = oldformat;
+				prefixlen = tok - oldformat - 1;
+				suffix = tok + 1;
+				/*
+				 * Construct a new format string from the
+				 * prefix (i.e., the part of the old fromat
+				 * from its beginning to the currently handled
+				 * "%N" conversion specification, the
+				 * nanoseconds, and the suffix (i.e., the part
+				 * of the old format from the next token to the
+				 * end).
+				 */
+				if (asprintf(&newformat, "%.*s%.9ld%s",
+				    (int)prefixlen, prefix, nsec,
+				    suffix) < 0) {
+					err(1, "asprintf");
+				}
+				free(oldformat);
+				tok = newformat + prefixlen + 9;
+			}
+			seen_percent = false;
+			break;
+		default:
+			seen_percent = false;
+			break;
+		}
+	}
+
+	ret = strftime(s, maxsize, newformat, t);
+	free(newformat);
+	return (ret);
+}
+
 static void
 badformat(void)
 {
@@ -374,7 +452,7 @@ static void
 usage(void)
 {
 	(void)fprintf(stderr, "%s\n%s\n%s\n",
-	    "usage: date [-jnRu] [-I[date|hours|minutes|seconds]] [-f input_fmt]",
+	    "usage: date [-jnRu] [-I[date|hours|minutes|seconds|ns]] [-f input_fmt]",
 	    "            "
 	    "[ -z output_zone ] [-r filename|seconds] [-v[+|-]val[y|m|w|d|H|M|S]]",
 	    "            "
diff --git a/bin/date/tests/format_string_test.sh b/bin/date/tests/format_string_test.sh
index a3e2939bfe5c..c2fe2111373f 100755
--- a/bin/date/tests/format_string_test.sh
+++ b/bin/date/tests/format_string_test.sh
@@ -30,6 +30,17 @@ check()
 	    date -r ${TEST2} +%${format_string}
 }
 
+atf_test_case flag_r_file_test
+flag_r_file_test_body()
+{
+	local file
+
+	file="./testfile"
+	touch "$file"
+	atf_check -o "inline:$(stat -f '%9Fm' "$file")\n" \
+		date -r "$file" +%s.%N
+}
+
 format_string_test()
 {
 	local desc exp_output_1 exp_output_2 flag
@@ -98,6 +109,8 @@ iso8601_${desc}_parity_body() {
 
 atf_init_test_cases()
 {
+	atf_add_test_case flag_r_file_test
+
 	format_string_test A A Saturday Monday
 	format_string_test a a Sat Mon
 	format_string_test B B February November
@@ -118,6 +131,7 @@ atf_init_test_cases()
 	format_string_test l l " 7" " 9"
 	format_string_test M M 04 20
 	format_string_test m m 02 11
+	format_string_test N N 000000000 000000000
 	format_string_test p p AM PM
 	format_string_test R R 07:04 21:20
 	format_string_test r r "07:04:03 AM" "09:20:00 PM"
@@ -143,6 +157,5 @@ atf_init_test_cases()
 	iso8601_string_test hours hours "" "1970-02-07T07+00:00" "2001-11-12T21+00:00"
 	iso8601_string_test minutes minutes "" "1970-02-07T07:04+00:00" "2001-11-12T21:20+00:00"
 	iso8601_string_test seconds seconds "" "1970-02-07T07:04:03+00:00" "2001-11-12T21:20:00+00:00"
-	# BSD date(1) does not support fractional seconds at this time.
-	#iso8601_string_test ns ns "" "1970-02-07T07:04:03,000000000+00:00" "2001-11-12T21:20:00,000000000+00:00"
+	iso8601_string_test ns ns "" "1970-02-07T07:04:03,000000000+00:00" "2001-11-12T21:20:00,000000000+00:00"
 }