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Evaluate Expression within awk

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# 1  
Old 09-12-2014
Evaluate Expression within awk
I want to create a conditional expression string and pass in an awk script. My script is as below...

Code:
comm="\$3 == "hello"" 

awk -F "^T" -v command="${comm}" ' {

     if ( command )   {     print "hye"   } 
}' test

But the statement "if ( command )" always evaluates to true which is not correct. I want to know the correct way of executing this statement..
On Running...

Code:
./test_awk.sh
hye ( not correct )

Test file has following ( just a sample )

Code:
hello^Thye^Tbye

Please help....
# 2  
Old 09-12-2014
The way you're doing it, command is a string; not an awk condition to be processed. Since the string $3 == hello is not an empty string and does not evaluate to "0", testing the string yields TRUE. The following should work but it gets a lot more complex if the operator you want varies from invocation to invocation rather than being a constant ==

Code:
field=3
value="hello" 

awk -F "^T" -v fn="$field" -v val="$value" '
{     if ( $fn == val )   {     print "hye"   } 
}' test

This User Gave Thanks to Don Cragun For This Post:
Saikat123
# 3  
Old 09-12-2014
Thanks and need more help
Quote:
Originally Posted by Don Cragun
The way you're doing it, command is a string; not an awk condition to be processed. Since the string $3 == hello is not an empty string and does not evaluate to "0", testing the string yields TRUE. The following should work but it gets a lot more complex if the operator you want varies from invocation to invocation rather than being a constant ==

Code:
field=3
value="hello" 

awk -F "^T" -v fn="$field" -v val="$value" '
{     if ( $fn == val )   {     print "hye"   } 
}' test

Thanks Sir for the reply.. But I want to formulate a complex string command to be passed to the awk function.. For example, I want to have an expression like this

Code:
str="($3 > 0 && $1 == 10) || ($2 == 100)"

Then I want it to be evaluated in awk like

Code:
awk -v command=${str} '{
if ( $command )
    print success
fi }' test

How can I achieve this kind of functionality

Many thanks in advance
Last edited by vbe; 09-12-2014 at 06:20 AM.. Reason: insert between the code tags ! Thanks
# 4  
Old 09-12-2014
Try putting your complex condition into a file and run awk with the -f option: awk -f file
# 5  
Old 09-12-2014
But what is the logic to be used in this case??
# 6  
Old 09-12-2014
Try
Code:
echo '{if (($3 > 0 && $1 == 10) || ($2 == 100)) print "success"}' > awkscript
awk -f awkscript file4

You can have multiple script files on the command line.
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