[patch] output of rsync -n truncated

[Dick Streefland]

I noticed that the output of "rsync -n" is sometimes truncated.
Even when you repeat the same command, the output may be different.
I'm using rsync-2.5.5 on a Debian woody system with ext3 file systems.
One scenario to reproduce this behavior is someting like this:

# rsync -aR /usr/share/zoneinfo /tmp 
# rsync -n -avRH localhost:/usr/share/zoneinfo /tmp
receiving file list ... done
usr/share/zoneinfo/Asia/Dhaka => usr/share/zoneinfo/Asia/Dacca
usr/share/zoneinfo/Asia/Thimphu => usr/share/zoneinfo/Asia/Thimbu
usr/share/zoneinfo/PRC => usr/share/zoneinfo/Asia/Shanghai
usr/share/zoneinfo/Asia/Chungking => usr/share/zoneinfo/Asia/Chongqing
usr/share/zoneinfo/Hongkong => usr/share/zoneinfo/Asia/Hong_Kong
usr/share/zoneinfo/ROC => usr/share/zoneinfo/Asia/Taipei
[...]
wrote 16 bytes  read 37138 bytes  24769.33 bytes/sec
total size is 865270  speedup is 23.29
# rsync -n -avRH /usr/share/zoneinfo /tmp
building file list ... done
usr/share/zoneinfo/Asia/Dhaka => usr/share/zoneinfo/Asia/Dacca
usr/share/zoneinfo/Asia/Thimphu => usr/share/zoneinfo/Asia/Thimbu
wrote 37134 bytes  read 20 bytes  74308.00 bytes/sec
total size is 865270  speedup is 23.29

As you can see, the output of the last command is truncated.

The problem is that the output is written in non-blocking mode, and
that when the write() returns EAGAIN, the output may be discarded.
The attached patch adds a check for EAGAIN, and retries the write()
after 20 msec, which fixes the problem.

-- 
Dick Streefland                      ////             Altium Software BV
dick.streefland at altium.nl           (@ @)          http://www.altium.com
--------------------------------oOO--(_)--OOo---------------------------
-------------- next part --------------
--- rsync-2.5.5/log.c.orig	Mon Feb 18 20:51:12 2002
+++ rsync-2.5.5/log.c	Wed May 15 16:12:18 2002
@@ -116,7 +116,12 @@
 		int n = write(log_error_fd, el->buf+el->written, el->len - el->written);
 		/* don't check for an error if the best way of handling the error is
 		   to ignore it */
-		if (n == -1) break;
+		if (n == -1) {
+			if (errno == EAGAIN) {
+				msleep(20);
+			}
+			break;
+		}
 		if (n > 0) {
 			el->written += n;
 		}