Adding a number to column [line by line] - linux

Question

I have a text file named text: The row and columns are:
1 A 18 -180
2 B 19 -180
3 C 20 -150
50 D 21 -100
128 E 22 -130
10 F 23 -0
10 G 23 -0
What I want to do is to print out the 4th column with adding a constant number to each of the lines (except ==0). To do this is what I have done.
#!/bin/bash
FILE="/dir/text"
while IFS= read -r line
do
echo "$line"
done <"$FILE"
I can read the fourth column, but at the same time I want to put an argument $1 which will add a constant number to all of the lines in the fourth column except any line of the fourth column has ==0.
UPDATE:
The Desired output would be like: [the line has zeros are ignored]
-160
-160
-130
-80
-110
For example, the program name is example.sh. I want to add a number to the fourth column using an argument. Therefore it would be:
example.sh $1
where $1 could be any number I want to add in the 4th column.

Answer 1

You should awk here which will be faster than bash.
awk -v number="100" '$4!=0{$4+=number} 1' Input_file
number is an awk variable where you could set its value as per your need.
Explanation: Adding detailed explanation for above code.
awk -v number="100" ' ##Starting awk program from here and creating a variable number whose value is 100.
$4!=0{ ##Checking condition if 4th column is NOT zero then do following.
$4+=number ##Adding variable number to 4th column here.
}
1 ##Mentioning 1 will print edited/non-edited lines.
' Input_file ##mentioning Input_file name here.

Answer 2

In order to preserve your formatting using awk while adding the values to the 4th field, you can calculate the new value of the 4th field and then use sub to change the value without forcing awk to recalculate the fields and removing the whitespace.
For example, with your file stored as text and adding a value of 180 to the 4th field (except where 0), you could do:
awk -v n=180 '$4!=0 {newval=$4+n; sub(/[0-9]+$/,newval)}1' text
Doing so would produce the following output:
$ awk -v n=180 '$4!=0 {newval=$4+n; sub(/[0-9]+$/,newval)}1' text
1 A 18 0
2 B 19 0
3 C 20 30
50 D 21 80
128 E 22 50
10 F 23 -0
10 G 23 -0
If called withing a shell script, you could pass your $1 parameter as:
awk -v n="$1" '$4!=0 {newval=$4+n; sub(/[0-9]+$/,newval)}1' text
Though I would suggest checking that an argument has been provided to the script with:
[ -z "$1" ] && {
echo "error: value require as argument"
exit 1
}
or you can provide a default value -- up to you.

Answer 3

With bash:
while read -ra a; do [[ ${a[3]} != -0 ]] && ((a[3]+=42)); echo "${a[#]}"; done < file
Output:
1 A 18 -138
2 B 19 -138
3 C 20 -108
50 D 21 -58
128 E 22 -88
10 F 23 -0
10 G 23 -0