Check stale NFS
Here's a simple script to check whether the given directory (NFS mount point) is stale.
There are three points that needs some explanation here.
First, since any command that access the NFS file system would block
(unresponsive) iff the NFS is stale, I am using
read -t N for the
Second, I used process substitution feature of bash,
read -t 1 < <(...) will timeout after 1 second unless
=…= part finished within the timeout. bash will create a new
subshell to execute /list/ in
<(list) form. The problem is, if
any of list will access the stale NFS, the command will hang,
which makes the subshell also will hang. Even if the calling shell
script finished, the subshell would not terminated, leaving the
process in interruptible sleep state.
To prevent this, I recorded the sub-shell PID using
<(list) form. After =read= command, I deleted all possible
children of the subshell and the subshell itself. Note that using
$$ won't work in
<(list) form. =$$= represents the mother
shell's PID, not the sub-shell's.