Add a new -F flag which is a superset of -f. It will cause tail to

stat() the file being followed and do a close/reopen if the file has been
renamed and/or rotated.  This is damn useful for leaving running on files
in /var/log when newsyslog(8) rotates them.

4 files changed, 42 insertions, 4 deletions

diff --git a/usr.bin/tail/extern.h b/usr.bin/tail/extern.h
index f9a8bdf..0ec272d 100644
--- a/usr.bin/tail/extern.h
+++ b/usr.bin/tail/extern.h
@@ -48,5 +48,5 @@ int lines __P((FILE *, off_t));
 void ierr __P((void));
 void oerr __P((void));
 
-extern int fflag, rflag, rval;
+extern int Fflag, fflag, rflag, rval;
 extern char *fname;
diff --git a/usr.bin/tail/forward.c b/usr.bin/tail/forward.c
index 1c4020d..31f5ea6 100644
--- a/usr.bin/tail/forward.c
+++ b/usr.bin/tail/forward.c
@@ -86,6 +86,7 @@ forward(fp, style, off, sbp)
 {
 	register int ch;
 	struct timeval interval;
+	struct stat sb2;
 
 	switch(style) {
 	case FBYTES:
@@ -179,6 +180,21 @@ forward(fp, style, off, sbp)
 
 		(void) usleep(250000);
 		clearerr(fp);
+
+		if (Fflag && fileno(fp) != STDIN_FILENO &&
+		    stat(fname, &sb2) != -1) {
+			if (sb2.st_ino != sbp->st_ino ||
+			    sb2.st_dev != sbp->st_dev ||
+			    sb2.st_rdev != sbp->st_rdev ||
+			    sb2.st_nlink == 0) {
+				fp = freopen(fname, "r", fp);
+				if (fp == NULL) {
+					ierr();
+					break;
+				}
+				*sbp = sb2;
+			}
+		}
 	}
 }
 
diff --git a/usr.bin/tail/tail.1 b/usr.bin/tail/tail.1
index 8c96737..be5a03f 100644
--- a/usr.bin/tail/tail.1
+++ b/usr.bin/tail/tail.1
@@ -42,7 +42,11 @@
 .Nd display the last part of a file
 .Sh SYNOPSIS
 .Nm
-.Op Fl f Li | Fl r
+.Oo
+.Fl F |
+.Fl f |
+.Fl r
+.Oc
 .Oo
 .Fl b Ar number |
 .Fl c Ar number |
@@ -91,6 +95,20 @@ data to be appended to the input.
 The
 .Fl f
 option is ignored if the standard input is a pipe, but not if it is a FIFO.
+.It Fl F
+The
+.Fl F
+option implies the
+.Fl f
+option, but
+.Nm
+will also check to see if the file being followed has been renamed or rotated.
+The file is closed and reopened when
+.Nm
+detects that the filename being read from has a new inode number.
+The
+.Fl F
+option is ignored if reading from standard input rather than a file.
 .It Fl n Ar number
 The location is
 .Ar number
@@ -136,6 +154,7 @@ utility is expected to be a superset of the
 .St -p1003.2-92
 specification.
 In particular, the
+.Fl F ,
 .Fl b
 and
 .Fl r
diff --git a/usr.bin/tail/tail.c b/usr.bin/tail/tail.c
index 4c7ea6f..454ef65 100644
--- a/usr.bin/tail/tail.c
+++ b/usr.bin/tail/tail.c
@@ -54,7 +54,7 @@ static char sccsid[] = "@(#)tail.c	8.1 (Berkeley) 6/6/93";
 #include <err.h>
 #include "extern.h"
 
-int fflag, rflag, rval;
+int Fflag, fflag, rflag, rval;
 char *fname;
 
 static void obsolete __P((char **));
@@ -107,8 +107,11 @@ main(argc, argv)
 
 	obsolete(argv);
 	style = NOTSET;
-	while ((ch = getopt(argc, argv, "b:c:fn:r")) != -1)
+	while ((ch = getopt(argc, argv, "Fb:c:fn:r")) != -1)
 		switch(ch) {
+		case 'F':	/* -F is superset of (and implies) -f */
+			Fflag = fflag = 1;
+			break;
 		case 'b':
 			ARG(512, FBYTES, RBYTES);
 			break;