UNIX for Dummies Questions & Answers

alan, I just tried this stuff on a 9000/800 running HP-UX 11.00.

As a non-root user, I do get "mknod: must be super-user" with the command "/usr/sbin/mknod bla". But that is an illegal command. When I run the same command as root as get "illegal argument count" and a usage statement.

"/usr/sbin/mknod bla p" works fine for all users.

When I try:
cat bla &
echo "hello world" > bla

it works fine for me. I cannot reproduce that error. Yes, your fifo looks like it has both read and write for you.

Try switching shells. Just type "sh" which will start up a posix shell. It's very close to ksh. Does thast work any better? When I type "what /usr/bin/ksh", I get:

$ Revision: 82.10 $
Version 11/16/88

When I type "what /usr/bin/ksh", I get this
/usr/bin/ksh:
$Revision: 82.10.1.61 $
Version 11/16/88
PATCH_11_00: arith.o blok.o ctype.o defs.o edit.o echo.o expand.o fault.o io.o string.o stak.o word.o emacs.o vi.o hpux_rel.o args.o builtin.o cmd.o main.o msg.o print.o xec.o name.o macro.o error.o service.o test.o jobs.o history.o 02/09/04

I try switching to "sh". Same thing:
[dev1@la]/home/dev1% sh
[dev1@la]/home/dev1% mkfifo bla
[dev1@la]/home/dev1% cat bla &
[1] 13618
[dev1@la]/home/dev1% echo "hello world" > bla
sh: bla: Cannot create the specified file.
[dev1@la]/home/dev1% ls -l bla
prw-rw-r-- 1 dev1 cadev 0 Apr 15 13:37 bla|
[dev1@la]/home/dev1%

I also tried "csh" (just in case).Same thing:
% csh
% mkfifo bla2
% cat bla2 &
[1] 14009
% echo "hello world" > bla2
bla2: Is a directory.
% ls -l bla2
prw-rw-r-- 1 dev1 cadev 0 Apr 15 13:55 bla2
%

I am stumped. Could all of this be due that my userid is forbidden to use shell commands such as these? If it is the case, wouldn't I be getting an "error" message like "You are not authorized to ... this command..."??

This is an odd problem. What does "df -n ." and "bdf ." say? Also "cd /tmp" and repeat the mkfifo stuff.

"df -n" gives me (sorry, it's a lot of output)
/home/dev1 (cafs:/shared/homedirs/dev1) : nfs3
/users/oracle_backup (/dev/vgfc10/lvol1 ) : vxfs
/logs (/dev/vg00/lvol5 ) : vxfs
/opt (/dev/vg00/lvol6 ) : vxfs
/tmp (/dev/vg00/lvol4 ) : vxfs
/users/oracle (/dev/vgfc9/lvol1 ) : vxfs
/users/oracle_dump (/dev/vgfc8/lvol1 ) : vxfs
/users (/dev/vg00/lvol9 ) : vxfs
/usr (/dev/vg00/lvol7 ) : vxfs
/var (/dev/vg00/lvol8 ) : vxfs
/stand (/dev/vg00/lvol1 ) : hfs
/ (/dev/vg00/lvol3 ) : vxfs

"bdf" gives me (sorry, it's a lot of output too)
Filesystem kbytes used avail %used Mounted on
/dev/vg00/lvol3 307200 74281 218393 25% /
/dev/vg00/lvol1 199381 43308 136134 24% /stand
/dev/vg00/lvol8 2048000 1408577 599802 70% /var
/dev/vg00/lvol7 2048000 684491 1278326 35% /usr
/dev/vg00/lvol9 4517888 2896020 1520504 66% /users
/dev/vgfc8/lvol1 226443264 195601336 30601024 86% /users/oracle_dump
/dev/vgfc9/lvol1 20951040 17467736 3428880 84% /users/oracle
/dev/vg00/lvol4 409600 39856 347349 10% /tmp
/dev/vg00/lvol6 2048000 778280 1190425 40% /opt
/dev/vg00/lvol5 1048576 16444 967669 2% /logs
/dev/vgfc10/lvol1 492306432 348862320 142323464 71% /users/oracle_backup
cafs:/shared/homedirs/dev1
427924288 153771888 252415104 38% /home/dev1

[dev1@la]/home/dev1% cd /tmp
[dev1@la]/tmp% mkfifo bla
[dev1@la]/tmp% cat bla &
[1] 14891
[dev1@la]/tmp% echo "this is a test" > bla
this is a test
[dev1@la]/tmp% ls -l bla
prw-rw-r-- 1 dev1 cadev 0 Apr 15 19:52 bla|
[1] + Done cat bla &
[dev1@la]/tmp%

IT WORKS??!! Can you please explain why it worked in /tmp but not in my /home directory??

Driver, I'm thinking alan has an nfs mounted home directory with the nodevs option set. I would still expect fifos to work under that scenario, but I'm not totally sure.

alan, give Driver's program a try. Knowing which system call is failing with which error will help.

Okay...I need somebody to whack me on the head with a 2x4...DRIVER : you wrote "That should yield a more descriptive error message" when talking about this program. Are you saying it should return an error when I run it against my fifo? Because it does not...

(1)log in to my account:
[dev1@la]/home/dev1
(2)paste DRIVER's code vi new.c ...
(3) compile it: cc new.c -o new
(4)[dev1@la]/home/dev1% mkfifo bla
(5)[dev1@la]/home/dev1% cat bla &
[1] 15141
(6)[dev1@la]/home/dev1% ./new bla
x
[dev1@la]/home/dev1%

Looking at the output of bdf and df, it seems that indeed, the file system for my /home directory is NFS mounted while /TMP is on "vxfs". Why does it matter? Can somebody PLEASE enlighten me?

Okay....using ">>" instead of ">" worked.

[dev1@la]/home/dev1% mkfifo bla
[dev1@la]/home/dev1% cat bla &
[1] 15586
[dev1@la]/home/dev1% echo "test" >> bla
test
[dev1@la]/home/dev1% ls -l bla
prw-rw-r-- 1 dev1 cadev 0 Apr 15 20:36 bla|
[1] + Done cat bla &
[dev1@la]/home/dev1%

It also worked successfully with MKNOD. It seems to confirm that the file system is the culprit, correct?