Re: Race conditions
Jonas Sandberg (jsa@alv.teli.se)
Fri, 9 Dec 94 08:28:40 +0100
The race condition seems to work at ULTRIX 4.1
palantir% ls -l
total 46
-rwxr-xr-x 1 jonte 43860 Dec 9 08:18 race*
-rw-r--r-- 1 jonte 359 Dec 9 08:17 racetest.c
-rw-r--r-- 1 jonte 8 Dec 9 08:19 symlink
What i didn't get was if the 'symlink' really should be a link or a plain
file, as it was in 4.1. I tried to gcc the 'noddy little program'.
/jonas
In message <199412080339.OAA10567@huon.melb.cpr.itg.telecom.com.au>,
Luke Mewburn <lm@melb.cpr.itg.telecom.com.au> writes:
> After checking the man pages in Solaris 2.x and NetBSD, and confirming
-----deleted-------
>
> Unfortunately, it appears that older systems (possibly including SunOS 4
> and Ultrix) don't have this check.
I've just checked this out with a noddy program and built the
following table up (appended at the end of this post along with the
program). The most suprising part of this exercise for me was that I
could only find *one* OS that failed the check and created the file
pointed to be the symlink! Must be the pessimist in me.. :)
Notes:
1) The program was run as a normal user, not root.
2) The ls output looks like:
-rw-r--r-- 1 chris cs2 359 Dec 8 13:46 tst.c
lrwxrwxrwx 1 chris cs2 3 Dec 8 14:49 symlink -> ./a
-rwxr-xr-x 1 chris cs2 5492 Dec 8 14:50 tst*
Happy hunting, folks!
Chris
--
Christopher Samuel Phone: +44 1684 894644 chris@rivers.dra.hmg.gb
N-115, Defence Research Agency, St Andrews Road, Great Malvern, England, UK
postmaster@rivers.dra.hmg.gb usenet@rivers.dra.hmg.gb
----------------------------------------------------------
BAD - creates file with "open succeded (fh=3)":
HP-UX V7.05
----------------------------------------------------------
OK - fails with "open: File exists"
Ultrix 4.4
Ultrix 4.2
SunOS 4.1.3_U1
SunOS 4.1.3
SunOS 4.1.1
Solaris 2.1
Solaris 2.3
USL SVR4.2
Unixware 1.1.2
SCO 3.2 (ODT3)
Irix 5.2
HP-UX 9.05
NeXTstep 3.2
DRS/NX 6000 SVR4 Version 7 Level 2 Increment 2
Linux 1.1.64
----------------------------------------------------------
#include <stdio.h>
#include <fcntl.h>
static char message[]="testing";
int main(void)
{
int fh,retval;
fh=open("./symlink",O_RDWR|O_EXCL|O_CREAT,0644);
if(fh < 0)
{
perror("open");
}
else
{
printf("open succeded (fh=%d)\n",fh);
retval = write(fh,message,sizeof(message));
if( retval == -1 )
{
perror("write");
}
close(fh);
}
}
----------------------------------------------------------
/jonas
--
Jonas Sandberg jsa@alv.teli.se
Ericsson Radio Messaging AB +46 (0)8 719 2722 :phone
126 25 STOCKHOLM +46 (0)746-417320 :pager
SWEDEN
Disclaimer: I'm innocent, I haven't done anything ...