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Old 02-17-2012, 12:16 AM   #1
sysmicuser
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One liners for File system disk usage.


Hi,

I am trying to develop a script 1 liner to check disk usage on file system, if it is more than 80% it should send email if it is less than than it should echo say "Do nothing"

However for both of them I am having some syntax problems

1)if [[ (df -P|egrep -i 'test'|awk '{print$5}'|sed 's/%//') >= 80 ]]; then mailx -s "test FULL" testme@testmail.com else echo "do nothing" fi

I am getting error message like.
-bash: conditional binary operator expected
-bash: expected `)'
-bash: syntax error near `|'

If I do with single square brackets.

2) if [ (df -P|egrep -i 'test' |awk '{print$5}'|sed 's/%//') >= 80 ]; then mailx -s "test is FULL" testme@testmail.com else echo "do nothing" fi
-bash: syntax error near unexpected token `df'

What the heck is difference between if with single and double square brackets Guru's?

Please assist in my understanding.

Many thanks.
 
Old 02-17-2012, 12:21 AM   #2
chrism01
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http://tldp.org/LDP/abs/html/testcon...ml#DBLBRACKETS
 
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Old 02-17-2012, 12:40 AM   #3
sysmicuser
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Thanks for that Chris. I got a good understanding that [[ ]] are fairly strong than that of [ ] and that when it says conditional binary operator expected so I changed >= to -ge but still that error prevails...

Last edited by sysmicuser; 02-17-2012 at 12:46 AM.
 
Old 02-17-2012, 12:47 AM   #4
sysmicuser
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Lastly I have now introduced " " and " " within if conditional statement but still no good and it just hangs...

Here we go this is code.

if [[ "(df -P|egrep -i 'test' |awk '{print$5}'|sed 's/%//')" -ge "80" ]]; then mailx -s "test" test@testmail.com else echo "do nothing" fi;

Last edited by sysmicuser; 02-17-2012 at 12:52 AM.
 
Old 02-17-2012, 12:56 AM   #5
grail
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Personally when doing math comparisons I like to keep with the familiar operators, hence it is often just easier to use (()), eg.
Code:
if (( $(df -P | awk 'tolower($0) ~ /test/{print strtonum($5)}') >= 80 ))
then
    echo yep
else
    echo nup
fi
 
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Old 02-17-2012, 01:17 AM   #6
sysmicuser
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grail mate you come up with some sensational command ! need some time to digest, your stuff is working but I would love to understand where I am making mistake and where I do need to improve. weekend is going to be with shell scripting
 
Old 02-17-2012, 01:25 AM   #7
grail
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Have a close look between your df ... statement and mine (hint: look before df command)
 
Old 02-17-2012, 09:01 AM   #8
sysmicuser
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That is my gross mistake, "$" sign is the answer
 
Old 02-17-2012, 09:49 AM   #9
uhelp
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(( )) denotes an calculation
$( cmd ) substitutes the expression with the output of cmd. This is called a "parameter expansion"
( cmd; cmd2 | cmd3 ) just groups all comamnds avoiding a subshell
<( cmd ) executes cmd and connects stdout of cmd to a filedescriptor from which the calling script reads.

[someTest] is the portable POSIX way of testing. Available in nearly each and every shell.
[[ someTest ]] is the modern bash way. Has a lot more features and makes script easier to read.
 
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Old 02-17-2012, 10:02 AM   #10
sysmicuser
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Cooking !

Getting closer but still not that close

Now the one liner is working but still i am having issues using mailx

if [[ $(df -P|egrep -i '/test'|awk '{print$5}'|sed 's/%//') -ge 80 ]]; then mailx -s "test is FULL" email@removed </tmp/$$; else echo "do nothing"; fi

The above one liner remains in hang state unless and until I perform Ctl-C operation (twice).

How can get work around with it satisfying as it becomes truly one liner.

Say for example

echo "test is more than 80% FULL" > /tmp/$$;if [[ $(df -P|egrep -i '/test'|awk '{print$5}'|sed 's/%//') -ge 80 ]]; then mailx -s "test is FULL" email@removed </tmp/$$; else echo "do nothing"; fi

This works but it doesn't have charm of being a one liner.

But say if this comes the only one way then what should we do to.
1 echo statement reflects right value of %percentage used rather than just 80?
 
  


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