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awk - passing variables in and out

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# 1  
Old 09-17-2015
awk - passing variables in and out
Am looking to pass some Linux environment variables into AWK , can I simply use the -v option ?

Code:
awk -F: -v AHOME=$HOME '{ if [ $1 == "X" ] 
                                        {rm AHOME/file.txt
                                         a=2 }  }'
                                         config.txt

how do I pass variable a FROM Awk (defined and value set in Awk) back to the parent shell script ?
Last edited by alldbest; 09-17-2015 at 01:48 PM..
# 2  
Old 09-17-2015
Please use code tags as required by forum rules!

You can't. awk prints to stdout that can be redirected, or to files defined within. You can use "command substitution" to assign a command's stdout to a variable, or you can pipe awk's stdout into a read command to read the variables.
# 3  
Old 09-17-2015
thanks, added the correct code tags.

So looks like using print > file within Awk and then grabbing the value from the file from the parent shell is one of my options.
# 4  
Old 09-17-2015
You don't pass variables out, because awk is not a shell builtin and can't modify the shell's variables for you.

If you have multiple values to extract, file would be best. If it's just one, VAR=$(awk '{ stuff }' inputfile )
# 5  
Old 09-17-2015
Pass in variables: awk -v var1="$var1" -v var2="$var2" ...
For safety in the shell each $variable in command arguments should be quoted!
Pass out variables works with eval:
Code:
eval `
echo 2 3 | awk '{ result=$1+$2; printf "result='\'%s\''\n", result }'
`
echo "$result"

For safety the variable's value is put in 'ticks'.
NB this method works with more than one variables.
For one variable the following is much simpler:
Code:
result=`
echo 2 3 | awk '{ result=$1+$2; print result }'
`
echo "$result"

NB the old-style backticks can be replaced by $( ) e.g.
Code:
result=$(
 echo 2 3 | awk '{ result=$1+$2; print result }'
)

Last edited by MadeInGermany; 09-17-2015 at 05:47 PM..
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