I think I've just found a bug in the /proc filesystem in the 2.1.125ac2
kernel.
It's possible that an entry remains in the proc fs after the command has
exited. It seems to me that it happens if we run an `ls -l' command in the
/proc/$pid/fd directory while the command runs. After the command exits,
`ls /proc' doesn't write $pid, but /proc/$pid still exists. See the log file
below.
Two more questions about /proc/$pid/fd:
1. Instead of 64, could the "correct" length of the symlinks be returned?
2. When a file is deleted, the string "/tmp/x (deleted)" could rather be
"deleted:/tmp/x". This is because it's more similar to the pipe: and
socket: ones, and a normal file _can_ have the name "/tmp/x (deleted)"
so it cannot be told whether this really means a deleted file or not.
On the other hand, "deleted:/tmp/x" can not be the full name of a real
file. So it would be more simplier and more consequent to parse the
"deleted:/tmp/x" notation within a program.
Bye
Egmont Koblinger
Here is the log file how I can invoke the bug:
egmont $ sleep 10 &
[1] 182
egmont $ ls -l /proc/182/fd
total 0
lrwx------ 1 egmont pupil 64 Oct 20 20:50 0 -> /dev/ttyp0
lrwx------ 1 egmont pupil 64 Oct 20 20:50 1 -> /dev/ttyp0
lrwx------ 1 egmont pupil 64 Oct 20 20:50 2 -> /dev/ttyp0
egmont $ ##### wait ten seconds
[1]+ Done sleep 10
egmont $ ls /proc | grep 182
egmont $ ls -l /proc/182
ls: /proc/182/exe: Permission denied
ls: /proc/182/root: Permission denied
ls: /proc/182/cwd: Permission denied
total 0
-r--r--r-- 1 root root 0 Oct 20 20:50 cmdline
-r--r--r-- 1 root root 0 Oct 20 20:50 cpu
lrwx------ 1 root root 0 Oct 20 20:50 cwd
-r-------- 1 root root 0 Oct 20 20:50 environ
lrwx------ 1 root root 0 Oct 20 20:50 exe
dr-x------ 2 egmont pupil 0 Oct 20 20:50 fd
pr--r--r-- 1 root root 0 Oct 20 20:50 maps
-rw------- 1 root root 0 Oct 20 20:50 mem
lrwx------ 1 root root 0 Oct 20 20:50 root
-r--r--r-- 1 root root 0 Oct 20 20:50 stat
-r--r--r-- 1 root root 0 Oct 20 20:50 statm
-r--r--r-- 1 root root 0 Oct 20 20:50 status
egmont $ ##### well, that's it
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