awk how to replace specific field with new value

Shell Programming and Scripting
1

I need to replace specific field (x) in a table with new value (y):

Input:

1 2 3 4
5 x 6 7
8 9 0 0

Output:

1 2 3 4
5 y 6 7
8 9 0 0

I have no idea how to do this.

2

replace all x into y?
or only in 2nd line?
or in lines that match some pattern? e.g. starts with 5?

the codes below change any x-fields to y only in the 2nd line.

awk '{if (NR==2)for(i=1;i<=NF;i++) $i=($i=="x")?"y":$i; print $0}' input
1 Like
3

This does it all. Remove parts to do one or the other.

awk '/^5/||(NR==2){for(i=1;i<=NF;i++)if($i=="x")$i="y";print $0};/^[^5]/&&(NR!=2)' input
4 
awk 'NR==2 {sub(" x ", " y ")}1' input

or with sed

sed '2s/ x / y /' input
5

Thanks, it works.

But I have set of data and in every file instead of "x" is different number. I need to clear this field and after that fill with new value for example 100 (for all data sets).

data 1

0 0 0 0
0 3 0 0
0 0 0 0

data 2

0 0 0 0
0 1 0 0
0 0 0 0

data 3

0 0 0 0
0 8 0 0
0 0 0 0

output

0 0 0 0
0 100 0 0
0 0 0 0

6

Is the value you want to replace always the second value in the second row? Or is it the only nonzero value in the file? Do the files only have 3 rows?

7

I want to replace always second value in second row.

My real input data has thousands of rows and about 20 columns with different numbers. In every file I want to replace value in specific field (for example second row, second column).

8 
 awk -v row=2 -v col=2 'FNR==1{print FILENAME} FNR==row{$col="100"}1' datafile*

You can specify the row and col where you want to make change.

9 
awk '{if (NR==2) $2=100; print $0}' input

this handles "only the 2nd column/field in 2nd line"

10

It works!

Thank You.

11

awk '{if(NR==2)$2=100;print $0}' input

---------- Post updated at 10:17 AM ---------- Previous update was at 10:16 AM ----------

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