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Capturing a non-result of a command

 
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# 1  
Old 05-26-2009
Capturing a non-result of a command
The following pseudo-code should be clear to what I am trying to achieve:
Code:
if [ {nothing is returned from kldstat | grep linux} ]; then
	kldload linux
	echo 'linux_enable="YES"' >> /etc/rc.conf
fi

What is the proper syntax or operator for the test?
Thanks in advance
# 2  
Old 05-26-2009
Do you mean the result of the [ command kldstat|grep linux ] returns nothing?
(sorry no linux around...) why not put the result in a variable then test the variable?
# 3  
Old 05-26-2009
Thank you for your response. Yes, in some cases the following occurs:
Code:
# kldstat | grep linux
#

This is FreeBSD 7.1 by the way, whereby Linux emulation needs to be enabled. So your suggestion means I need to evaluate $? or use trap somehow? Please advise.
# 4  
Old 05-26-2009
Quote:
Originally Posted by figaro
Thank you for your response. Yes, in some cases the following occurs:
Code:
# kldstat | grep linux
#

This is FreeBSD 7.1 by the way, whereby Linux emulation needs to be enabled. So your suggestion means I need to evaluate $? or use trap somehow? Please advise.
Something like this?

Code:
kldstat | grep linux > /dev/null 2>&1
if [ $? == 0 ]; then
  # linux found
fi

Regards
# 5  
Old 05-26-2009
Or ...

Code:
if ! kldstat | grep linux; then
   # do something
fi

Or ...

Code:
if [ $(kldstat | grep -c linux) -eq 0 ]; then
    # do something
fi

# 6  
Old 05-26-2009
Thanks, your suggestions worked.
 
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