How can I format my grep output to show line numbers at the end of the line, and also the hit count?

Question

I'm using grep to match string in a file. Here is an example file: example one, example two null, example three, example four null, `grep -i null myfile.txt` returns example two null, example four null, How can I return matched lines together with their line numbers like this: example two null, - Line number : 2 example four null, - Line number : 4 Total null count : 2 I know -c returns total matched lines, but I don't how to format it properly to add `total null count` in front, and I don't know how to add the line numbers. What can I do?

Answer 1

The best way to tackle the full problem is to a short script. Here are the elements of it.

The main way to pull line numbers using grep is the "-n" option.

pfry@DESKTOP-S8LEH5G:~$ grep -n null myfile.txt

2:example two null

4:example four null

But this is not in the desired format. However there are ways to process each line returned by the command using the while/read construct. Here is the full script:

#!/bin/bash # Use grep to parse each line of file

input="myfile.txt" while IFS= read -r line ; do

ln=`echo $line | cut -d":" -f1` # Retrieve line # from start of line

pos=`echo $((${#ln} + 2))` # Determine beginning position

rest=`echo $line | cut -c $pos-` # Assign rest of line

echo $rest "- Line number:" $ln # Output in desired format

done <<< $(grep -n null $input)

echo -e "\nTotal null count: `grep -c null $input`"

Noticed that the actual "grep -c" command is redirected in using the $() nomenclature and a triple input redirect symbol.

This script will work no matter how many digits are in the line number count. It will also work regardless of other colons showing up in the input file.

You can also see how the last line is formatted.The "echo -e" command is used to insert a leading newline with the "\n" symbol. Here's the output:

pfry@DESKTOP-S8LEH5G:~$ myscript.sh

example two null - Line number: 2

example four null - Line number: 4

Total null count: 2