From 7ea0732c554f65ee52af30c8f6d601e1ba4ee034 Mon Sep 17 00:00:00 2001
From: ftrvxmtrx <devnull@localhost>
Date: Thu, 8 May 2014 14:29:44 +0200
Subject: [PATCH] tail: fix follow for empty files (thanks cinap_lenrek)

---
 sys/src/cmd/tail.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/sys/src/cmd/tail.c b/sys/src/cmd/tail.c
index 572224749..e8717dc50 100644
--- a/sys/src/cmd/tail.c
+++ b/sys/src/cmd/tail.c
@@ -8,6 +8,7 @@
  * the simple command tail -c, legal in v10, is illegal
  */
 
+vlong	fend;
 long	count;
 int	anycount;
 int	follow;
@@ -111,7 +112,7 @@ main(int argc, char **argv)
 	else
 	if(units==LINES && origin==BEG)
 		skip();
-	if(follow && seekable)
+	if(follow && (seekable || fend == 0))
 		for(;;) {
 			static Dir *sb0, *sb1;
 			trunc(sb1, &sb0);
@@ -368,5 +369,6 @@ usage(void)
 static int
 isseekable(int fd)
 {
-	return seek(fd, 0, 2) > 0 && seek(fd, 0, 0) == 0;
+	fend = seek(fd, 0, 2);
+	return fend > 0 && seek(fd, 0, 0) == 0;
 }