How to increment column using AWK

Question

I have the following file pattern:

insert_buffer cell_a 
insert_buffer cell_b
insert_buffer cell_b
...

I want to add one more column to the end of each line with incremented number. e.x. 0,1,2,3...:

insert_buffer cell_a name_0
insert_buffer cell_b name_1
insert_buffer cell_b name_2
...

How do I for loop using awk? Or any other solution is fine.

Answer 1

$ awk '{$(NF+1) = "name_"(NR-1)} 1' file
insert_buffer cell_a name_0
insert_buffer cell_b name_1
insert_buffer cell_b name_2

If you want to use your own variable in place of the built-in record count NR, then for example

$ awk '{$(NF+1) = "name_"i++} 1' file
insert_buffer cell_a name_0
insert_buffer cell_b name_1
insert_buffer cell_b name_2

If you want to insert the new field elsewhere, then one way to do that is to prepend or append it to an existing field, along with an additional output field separator OFS e.g. to insert before the second field

$ awk '{$2 = "name_"i++ OFS $2 } 1' file
insert_buffer name_0 cell_a
insert_buffer name_1 cell_b
insert_buffer name_2 cell_b

Answer 2

This can be done using the sed editor as given:

Note that since sed has no notion of arithmetic, it can be done by other means.

the variable $n stores the column number where you want the new data placed.

n=2;
sed -ne 1i\\ -e 0 -e p\;= yourfile |\
sed -nE "N;s/\S\+/&\n/$n;s/\(.*\)\n\(.*\)\n/\2 name_\1 /p"

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Results

insert_buffer name_0  cell_a
insert_buffer name_1  cell_b
insert_buffer name_2  cell_c