CODEWITHSUNDEEP
bash
sknimo
sknimo

Reputation: 23

Getting awk working properly in a for loop

I am trying to extract the second column out of 22 different files. I get a correct output when working on a single file but when in a loop, in each file it concatenates in series the 2 column of several different files in one. Can anybody please help me.

for i in f*
do
    awk '{print $2}' f* > a_$i
done

Upvotes: 2

Views: 80

Answers (2)

John1024
John1024

Reputation: 113814

This does what you want:

awk '{print $2 >"a_"FILENAME}' f*

For every file starting with the letter f, this writes its second columns to a new file that starts with a_.

The output files have the same number of rows as the input but the output has only the second column.

Note that the above works because > means something somewhat different in awk than it does in shell.

Example

Suppose that we have a series of files like:

$ cat f1
One 1
One 11

Now, let's run the awk command:

$ awk '{print $2 >"a_"FILENAME}' f*

When this is done, there are a series of a_* files in the directory, such as:

$ cat a_f1
1
11

Upvotes: 1

Avinash Raj
Avinash Raj

Reputation: 174696

Change your command like,

for i in f*
do
    awk '{print $2}' "$i" > "a_$i"
done

One-liner,

for i in f*; do awk '{print $2}' "$i" > "a_$i"; done

You need to replace f* in your awk command with $i which stores the current file name.

Upvotes: 2

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