ccdn@levels.sait.edu.au (DAVID NEWALL) (10/18/88)
I have discovered a bug in System V Unixes. Under certain circumstances,
ps -f displays "junk" in the login name field. This bug exists on our NCR
Tower 32/600's which are running NCR OS 01.03.02 (Unix V.2) and also on my
Stride 440 (Unix/68 V.1). This does not appear to be a problem in BSD4.2
- at least, the bug does not occur on our Sun 3/60's (SUNOS 3.2).
This bug occurs when a logged in user has a login name which is 8 characters
long (could be longer; I haven't checked), and when the entry in /etc/passwd
that follows that user's has a user number greater than 256.
The "junk" that is displayed is the user's login name followed by the next
user's user number mod 256 (as a character) followed by that (second) user's
login name. Similarly for third and subsequent lines.
For example:
$ who am i
user1234
$ tail -3 /etc/passwd
user1234:likjlasdfSDF:100:100:User 1234:/usr/1234:/bin/sh
user2345:89kkakkik2kH:321:100:User 2345:/usr/2345:/bin/sh
user3456:jKLJD983.8Hs:322:100:User 3456:/usr/3456:/bin/sh
$ ps -f
UID PID PPID C TTY TIME COMMAND
user1234Auser2345Buser3456 14165 1 2 15:54:52 05 0:03 sh
user1234Auser2345Buser3456 14166 14165 0 15:54:57 05 0:00 ps -f
David Newall Phone: +61 8 343 3160
Unix Systems Programmer Fax: +61 8 349 6939
Academic Computing Service E-mail: ccdn@levels.sait.oz.au
SA Institute of Technology Post: The Levels, South Australia, 5095debra@alice.UUCP (Paul De Bra) (10/21/88)
In article <533@levels.sait.edu.au> ccdn@levels.sait.edu.au (DAVID NEWALL) writes: >I have discovered a bug in System V Unixes. Under certain circumstances, >ps -f displays "junk" in the login name field. This bug exists on our NCR >... > $ ps -f > UID PID PPID C TTY TIME COMMAND > user1234Auser2345Buser3456 14165 1 2 15:54:52 05 0:03 sh > user1234Auser2345Buser3456 14166 14165 0 15:54:57 05 0:00 ps -f > As far as I know this bug extremely old. The reason some programs show this bug is that the internal representation of user names is done with an 8-character array. This means that usernames consisting of 8 characters are not 0-terminated. We worked around the problem by not allowing login names of more than 7 characters on any of our systems. Paul. -- ------------------------------------------------------------------------- |debra@research.att.com | uunet!research!debra | att!grumpy!debra | -------------------------------------------------------------------------