On 2016-12-01 15:32, Mike Fleetwood wrote:
On 1 December 2016 at 18:43, Austin S. Hemmelgarn <ahferro...@gmail.com> wrote:
Currently, `btrfs device stats` returns non-zero only when there was an
error getting the counter values. This is fine for when it gets run by a
user directly, but is a serious pain when trying to use it in a script or
for monitoring since you need to parse the (not at all machine friendly)
output to check the counter values.
This patch adds an option ('-s') which causes `btrfs device stats`
to set bit 7 in the return code if any of the counters are non-zero.
This greatly simplifies checking from a script or monitoring software
if any errors have been recorded. In the event that this switch is
passed and an error occurs reading the stats, the return code will have
bit 0 set (so if there are errors reading counters, and the counters
which were read were non-zero, the return value will be 129).
I don't think using bit 7 is a good idea. Bash (and I think all
shells) report exist status 128+SIGNUM when the process is killed by a
signal. I.e. status 129 would be returned when a process is killed by
SIGHUP.
Perhaps bit 6 would be OK to use.
Ah, you're right, I actually completely forgot about this. I'll send an
updated version later today.
Thanks,
Mike
https://tiswww.case.edu/php/chet/bash/bashref.html#Exit-Status
"Exit statuses fall between 0 and 255, though, as explained below, the
shell may use values above 125 specially. ...
When a command terminates on a fatal signal whose number is N, Bash
uses the value 128+N as the exit status. ...
If a command is not found, the child process created to execute it
returns a status of 127. If a command is found but is not executable,
the return status is 126."
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