I agree it's a bit off-topic, but just to answer the question:
The "x" prefix for testing variables (more commonly the upper case "X",
because that's the example in the man page :-) is common practice to avoid
the test getting confused by unexpected values in the variable, In
particular, the test tends to throw the comparison out if the variable
should start with a "-". Prefixing the variable would convert this to
"X-", which is correctly processed by the test comparison.
For example:
VAR="-value"
[ "$VAR" == "something" ] will fail, trying to process "-value" as a
qualifier.
[ "X$VAR" == "Xsomething" ] will correctly find an inequality
Cheers,
John
JOHN MARTIN
From: Ryan Novosielski <user-ae4522577e16@xymon.invalid>
To: xymon at xymon.com
Date: 31/05/2011 08:22
Subject: Re: [Xymon] Configuring Devmon for the first time
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The X is a trick that deals with empty variables, and I suppose keeps
some interpreters from complaining about doing a test on a blank variable.
I've seen this done frequently enough to know that people do it, but I
agree, it looks a little odd and I'm not sure I'd write a program that
way myself. This is off topic, but I'd love to know if anyone has any
comments on that particular thing. Shortcut to avoid needing to check
for empty variables I guess?
On 05/31/2011 12:57 AM, Josh Luthman wrote:That probably makes more sense then to use Lynx, good idea.
What's with the "x" in the variable?
Would you mind telling me what values you used for date?
Josh Luthman
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Direct: XXX-XXX-XXXX
XXXX Wayne St
Suite XXXX
Troy, OH XXXXX
On Tue, May 31, 2011 at 12:53 AM, David Baldwin
<user-cbbf693f2c89@xymon.invalid <mailto:user-cbbf693f2c89@xymon.invalid>>
wrote:
On 31/05/11 11:24 AM, user-7cb0f5662626@xymon.invalid
<mailto:user-7cb0f5662626@xymon.invalid> wrote:I've had issues with devmon not updating the bb-display and
everything going purple.
I've had this issue since day one (which is over two years now).
I created a "devmon watchdog" script that's runs every 5 min using
lynx (txt base html browser) which checks if the status of devmon
(shows as dm test) on bb-monitor. If its purple then I kill the
devmon process and start it up again....band-aid solution, but it
does the trick.
I no script expert, but can share the bash script if you want/need.
Here's mine (replace xymonserver with your hostname):
#!/bin/sh
COL=`bb xymonserver "hobbitdboard xymonserver.dm
<http://xymonserver.dm>; fields=color"`
if [ "x$COL" == "xpurple" ] ; then
(date "+%x %X restarting purple devmon"
/etc/init.d/devmon restart) | tee /var/log/devmon-restart.log | mail
-s "Restarting devmon" xymonadmin
fi
- --
- ---- _ _ _ _ ___ _ _ _
|Y#| | | |\/| | \ |\ | | |Ryan Novosielski - Sr. Systems Programmer
|$&| |__| | | |__/ | \| _| |user-ae4522577e16@xymon.invalid - 973/972.0922 (2-0922)
\__/ Univ. of Med. and Dent.|IST/CST-Academic Svcs. - ADMC 450, Newark
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