How do I append an output to existing rows?

Question

I'm running a command that outputs a list of numbers. I am using a for loop to run the command 5 times. For each output, I want to append those numbers to corresponding rows in an existing text file.

Command output:

# execute_command
20
30
480
50

Command with loop

for i in {1..5};
    # execute_command

Command output with loop

Before

This is just a text file I created.

cat:
rabbit:
car: 
can:

After

I want to append the command outputs to that existing text file.

first iteration

cat: 20
rabbit: 30
car: 480
can: 50

second iteration

cat: 20, 30
rabbit: 30, 50
car: 480, 60
can: 50, 70

third iteration

cat: 20, 30, 90
rabbit: 30, 50, 20
car: 480, 60, 20
can: 50, 70, 40

fourth iteration

cat: 20, 30, 90, 40, 
rabbit: 30, 50, 20, 35
car: 480, 60, 20, 60
can: 50, 70, 40, 70

fifth iteration

cat: 20, 30, 90, 40, 90 
rabbit: 30, 50, 20, 35, 50
car: 480, 60, 20, 60, 40
can: 50, 70, 40, 70, 10

Please help me. Thanks very much!

In the second and third iteration, where are you getting those numbers? From the command that outputs the list of numbers? If so, then how that command is working? Does it generate 4 random numbers each iteration? — Edgar Magallon
– Edgar Magallon, Commented Nov 10, 2022 at 20:39
@EdgarMagallon Yes, in the second and third iteration, the numbers are the output of the command. The actual command is a benchmark that generates/outputs scores. — ttttttt
– ttttttt, Commented Nov 10, 2022 at 20:44
Could you edit your question to provide what your command actually does? Because I'm not sure if you have to call the command each iteration or maybe you call it just once — Edgar Magallon
– Edgar Magallon, Commented Nov 10, 2022 at 21:03
@EdgarMagallon I just updated the question with more details. The command itself executes once and I am running the command in a for loop. — ttttttt
– ttttttt, Commented Nov 10, 2022 at 21:16

AdminBee · Accepted Answer · 2022-11-11 11:41:48Z

Here is pointer using sed and paste commands.

Your base_file (containing the column with cat:, rabbit: etc.) has four rows. You need to systematically "move" and paste the top four rows from your numbers_list (i.e. the output of your command) until the list is exhausted.

Consider the following command:

sed -n '1,4p' numbers_list | paste base_file -

which gives:

cat:    20
rabbit: 30
car:    480
can:    50

This output is your next base_file. You could put that in a temporary file called nbase_file with:

sed -n '1,4p' numbers_list | paste base_file - >nbase_file

then

mv nbase_file base_file

Now delete the top four lines in the numbers_list:

sed -i '1,4d' numbers_list

and repeat the process using a loop.

Note that the new items are pasted tab-separated. So you might like to use -d "," with paste command if you want comma as delimiter.

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