Question

file.txt is as below :

gui : 789
gui : 789
gui : 789
gui : 789
abc : 120

The followibng gives o/p as

$ grep -n "gui : 789" file.txt | cut -f1 -d: 
1
2
3
4

If there are N number of such gui : 789 , how to store the line numbers of the same ?

Answer 1

You can use this awk 1 liner:

awk '/gui : 789/{print NR}' file

To process this inside a loop:

while read l
do
   echo $l
done < <(awk '/gui : 789/{print NR}' file)

EDIT: These command will work for any number of matches in the file. To store output of above line numbers in an array:

arr=( $(awk '/gui : 789/{print NR}' x) )

later on process these array elements as:

echo ${arr[0]}
echo ${arr[1]}
...
echo ${arr[5]}