date(1): Add "-R" flag to use RFC 2822 date and time output format

rolinh · François Tigeot · commit 3ea318c6a5de · 2014-11-15T20:01:48.000+01:00
As stated in the man page, this is equivalent to use
"%a, %d %b %Y %T %z" as the output format while LC_TIME is set to the
"C" locale.

This is compatible with date(1) from the GNU core utilities.

Taken-from: FreeBSD

While here, remove $DragonFly$ line from man page.
diff --git a/bin/date/date.1 b/bin/date/date.1
@@ -30,17 +30,16 @@
 .\"
 .\"     @(#)date.1	8.3 (Berkeley) 4/28/95
 .\" $FreeBSD: src/bin/date/date.1,v 1.72 2005/02/13 22:25:09 ru Exp $
-.\" $DragonFly: src/bin/date/date.1,v 1.4 2005/07/20 20:05:46 cpressey Exp $
 .\"
-.Dd August 9, 2004
+.Dd November 15, 2014
 .Dt DATE 1
 .Os
 .Sh NAME
 .Nm date
 .Nd display or set date and time
 .Sh SYNOPSIS
 .Nm
-.Op Fl ju
+.Op Fl jRu
 .Op Fl r Ar seconds
 .Oo
 .Fl v
@@ -52,7 +51,7 @@
 .Ar ...
 .Op Cm + Ns Ar output_fmt
 .Nm
-.Op Fl jnu
+.Op Fl jnRu
 .Sm off
 .Op Oo Oo Oo Oo Ar cc Oc Ar yy Oc Ar mm Oc Ar dd Oc Ar HH
 .Ar MM Op Ar .ss
@@ -130,6 +129,16 @@ The
 .Fl n
 option suppresses this behavior and causes the time to be set only on the
 current machine.
+.It Fl R
+Use RFC 2822 date and time output format. This is equivalent to use
+.Dq Li %a, %d %b %Y \&%T %z
+as
+.Ar output_fmt
+while
+.Ev LC_TIME
+is set to the
+.Dq C
+locale.
 .It Fl r Ar seconds
 Print the date and time represented by
 .Ar seconds ,
diff --git a/bin/date/date.c b/bin/date/date.c
@@ -58,12 +58,14 @@ static void setthetime(const char *, const char *, int, int);
 static void badformat(void);
 static void usage(void);
 
+static const char *rfc2822_format ="%a, %d %b %Y %T %z";
+
 int
 main(int argc, char **argv)
 {
 	struct timezone tz;
 	int ch, rflag;
-	int jflag, nflag;
+	int jflag, nflag, Rflag;
 	const char *format;
 	char buf[1024];
 	char *endptr, *fmt;
@@ -78,9 +80,9 @@ main(int argc, char **argv)
 	setlocale(LC_TIME, "");
 	tz.tz_dsttime = tz.tz_minuteswest = 0;
 	rflag = 0;
-	jflag = nflag = 0;
+	jflag = nflag = Rflag = 0;
 	set_timezone = 0;
-	while ((ch = getopt(argc, argv, "d:f:jnr:t:uv:")) != -1)
+	while ((ch = getopt(argc, argv, "d:f:jnRr:t:uv:")) != -1)
 		switch(ch) {
 		case 'd':		/* daylight savings time */
 			tz.tz_dsttime = strtol(optarg, &endptr, 10) ? 1 : 0;
@@ -97,6 +99,9 @@ main(int argc, char **argv)
 		case 'n':		/* don't set network */
 			nflag = 1;
 			break;
+		case 'R':
+			Rflag = 1;	/*RFC 2822 datetime format */
+			break;
 		case 'r':		/* user specified seconds */
 			rflag = 1;
 			tval = strtoll(optarg, &tmp, 0);
@@ -135,6 +140,9 @@ main(int argc, char **argv)
 
 	format = "%+";
 
+	if (Rflag)
+		format = rfc2822_format;
+
 	/* allow the operands in any order */
 	if (*argv && **argv == '+') {
 		format = *argv + 1;
@@ -159,6 +167,15 @@ main(int argc, char **argv)
 		usage();
 	}
 	vary_destroy(v);
+
+	if (format == rfc2822_format) {
+		/*
+		 * When using RFC 2822 datetime format, don't honor the
+		 * locale.
+		 */
+		setlocale(LC_TIME, "C");
+	}
+
 	strftime(buf, sizeof(buf), format, &lt);
 	printf("%s\n", buf);
 	if (fflush(stdout) != 0)
@@ -289,7 +306,7 @@ static void
 usage(void)
 {
 	fprintf(stderr, "%s\n%s\n",
-	    "usage: date [-jnu] [-d dst] [-r seconds] [-t west] "
+	    "usage: date [-jnRu] [-d dst] [-r seconds] [-t west] "
 	    "[-v[+|-]val[ymwdHMS]] ... ",
 	    "            "
 	    "[-f fmt date | [[[[[cc]yy]mm]dd]HH]MM[.ss]] [+format]");
