I am having the following structure(only one row)
col1 col2 col3 col4
----------------------
12 34 14 10
what I have to do is I have to fetch col2 and col4 and used that value in shell.
a=$(awk 'NR<2{$2}')
b=$(awk'NR<2{$4}')
and I have to use a and b in my shell scripting.
but this is not a good idea as I am using awk two times instead I am fetching value like this .
awk'NR<2{ a=$2;b=$4}'
but I dont know how can I use this a and b in my shell.
with eval you could assign more shell variables in one awk command. see the test below:
kent$ echo $a,$b
,
kent$ cat test
col1 col2 col3 col4
----------------------
12 34 14 10
kent$ eval $(awk 'NR==3{print "a="$2;print "b="$4}' test)
kent$ echo $a,$b
34,10
note that I just copied your input example, with header/titles etc. so in my script the data line is NR=3. you can adjust it if it is not in your case.
The read built-in is useful here.
read _ a _ b _ < <( tail -n +3 data.txt) # Assign the columns you don't care about to _
echo $a,$b
This avoids the use of eval, which should generally be avoided if you can find another option.
$ v=( $(awk 'NR==3{print $2 ORS $4}' file) )
$ a="${v[0]}"
$ b="${v[1]}"
$ echo "$a,$b"
34,10
