[DragonFlyBSD - Bug #3034] Tail -n 1 don't work on /proc/curproc/map

bugtracker-admin at leaf.dragonflybsd.org bugtracker-admin at leaf.dragonflybsd.org
Sun Nov 26 06:52:14 PST 2017

Issue #3034 has been updated by daftaupe.

After looking at this issue, it seems that it's because /proc/curproc/map has a size of 0.
In the forward.c code, in that case we're at line 150, calling function rlines : rlines(fp, off, sbp); 
But this function starts with a test :
if (!(size = sbp->st_size))
and as the size of the file is 0 it returns immediately and display the whole file instead of the number of lines specified on the cli.

The call of display_lines(fp, off) instead of rlines(fp, off, sbp) seems to fix this issue.

Bug #3034: Tail -n 1 don't work on /proc/curproc/map

* Author: cpk
* Status: New
* Priority: Normal
* Assignee: 
* Category: VFS subsystem
* Target version: 
If i run tail -n 1 /proc/curproc/map it will print 10 last lines.(wc says it is 11 but something is wrong here)
But then if i redirect output to file and then tail it it will print correct number of lines.

tail -n 1 /proc/curproc/map |wc -l 
    11     143    1111
tail -n 1 /proc/curproc/map > /tmp/tail-bug && tail -n 1 /tmp/tail-bug |wc 
    1      13      95

uname -a 
DragonFly dfly-0 4.6-RELEASE DragonFly v4.6.0rc2-RELEASE #2: Sun Jul 24 14:47:27 EDT 2016     root at www.shiningsilence.com:/usr/obj/home/justin/release/4_6/sys/X86_64_GENERIC  x86_64

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