Date: Fri, 13 Jun 2003 15:09:09 -0400 (EDT) From: Hal Burch <hburch@lumeta.com> To: FreeBSD-gnats-submit@FreeBSD.org Subject: bin/53288: tail will sometimes display more lines than it is told Message-ID: <20030613190909.1EDE35E3@hburch.corp.lumeta.com> Resent-Message-ID: <200306131910.h5DJAFWO094396@freefall.freebsd.org>
next in thread | raw e-mail | index | archive | help
>Number: 53288 >Category: bin >Synopsis: tail will sometimes display more lines than it is told >Confidential: no >Severity: non-critical >Priority: low >Responsible: freebsd-bugs >State: open >Quarter: >Keywords: >Date-Required: >Class: sw-bug >Submitter-Id: current-users >Arrival-Date: Fri Jun 13 12:10:14 PDT 2003 >Closed-Date: >Last-Modified: >Originator: Hal Burch >Release: FreeBSD 4.8-RC i386 >Organization: Lumeta Comporation >Environment: System: FreeBSD hburch.corp.lumeta.com 4.8-RC FreeBSD 4.8-RC #1: Wed Mar 26 17:25:56 EST 2003 root@hburch.corp.lumeta.com:/usr/obj/usr/src/sys/LOCAL i386 >Description: tail will sometimes output more lines than it is told if the file is being appended to. I believe this is occurs when data is written to the file after tail computes where to start displaying data, but before the display starts. >How-To-Repeat: Run one program that continuously prints out lines to a file: while [ 1 ]; do echo test; done > file While that is running, run a bunch of tails and compute their length for i in `seq 1 1000`; do tail file | wc -l | done > linecnt (In case it's not clear from the name, seq prints out 1 through 1000) Look at the distribution of the line counts that were displayed: sort -n linecnt | uniq -c On my run: 975 10 1 61 1 68 1 118 1 131 1 134 2 138 1 168 2 170 1 174 1 205 1 227 1 235 1 259 1 291 1 348 1 362 1 367 1 797 1 1170 1 1562 1 2198 1 5738 1 5861 >Fix: No known fix. tail could declare the end of the file (when -f is not done) to be the length of the file when it first touches it, but that could cause additional problems. >Release-Note: >Audit-Trail: >Unformatted:
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20030613190909.1EDE35E3>