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Sencer H.
Asked: 2013-08-02 05:32:38 +0800 CST

monit displays false number from my uptime script

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I've wrote a script for fetch real uptime and display in monit. But I think it displays just exit error status. My uptime script is:

#!/bin/sh
uptime=`uptime | awk -F " " '{print $3}'`
echo $uptime
exit $uptime

When I run it in terminal result is true

For example:

# uptime
 08:39:01 up 421 days, 19:54,  1 user,  load average: 0.06, 0.10, 0.06
# ./up_time.sh
421

Script works well. But when monit starts to run this script by up_time.conf file;

Program   Status     Last started                Exit value
days_up   Status ok  Thu, 01 Aug 2013 08:41:08      165

I saw on the browser. I guess that Exit value is the bash exit error code. I cant get why other script are works fine but this one does not do his job

Speaking of which, monit up_time.conf file is like this:

check program days_up with path "/etc/monit/scripts/up_time.sh"
    if status < 1 then alert
linux

2 Answers

  1. Best Answer

    The exit value of a commands are an unsigned 8 bit integer (aka a 1 byte). This means the exit value must be between 0 and 255. Your script seems to be trying to set an exit value of 412 which simply isn't valid as an exit code. The extra bits will get ignored, and so the actual value that gets returned is 156.

    412 = (0001 1001 1100), 156 = (1001 1100)

    Here is some output using bash's $? to demonstrate. The `$? variable is stores the exit value of the previous command.

    root@:~# bash -c 'exit 5' ; echo $?
5
root@:~# bash -c 'exit 253'; echo $?
253
root@:~# bash -c 'exit 255'; echo $?
255
root@:~# bash -c 'exit 256'; echo $?
0
root@:~# bash -c 'exit 257'; echo $?
1
root@:~# bash -c 'exit 412' ; echo $?
156
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  2. Why exit $uptime? Shouldn't it be just exit 0, meaning your shell script did finish OK?

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