CODEWITHSUNDEEP
linuxunixawksed
cloud36
cloud36

Reputation: 1066

Replace Column if equal to a specific value

I'm looking to replace the fourth column in a CSV if it equals N/A. I'm trying to change it to -1.
I can't seem to get this to work.

awk -F , '{ if($4 == "N/A") {$4 = -1} }' test.csv

Upvotes: 8

Views: 16716

Answers (4)

3nrique0
3nrique0

Reputation: 378

Here's an alternative for awk, and a shorter regex for sed: I used a regex containing the separator characters on both sides.

If your file is tab separated you can use \t instead of ,.

sed 's/,N\/A,/,-1,/g' infile.csv >  outfile.csv

Replace on the same file, good for big files, test before using !!

sed -i 's/,N\/A,/,-1,/g' infile.csv

Upvotes: 0

Avinash Raj
Avinash Raj

Reputation: 174836

You could also do this in sed,

$ sed -r 's/^([^,]*),([^,]*),([^,]*),N\/A,(.*)$/\1,\2,\3,-1,\4/g' file
a,b,c,d,e,f
1,2,3,4,5,6
44,2,1,-1,4,5
24,sdf,sdf,4,2,254,5
a,f,f,-1,f,4

Upvotes: 0

jaypal singh
jaypal singh

Reputation: 77175

You can use the following awk: 

awk -F, '{ $4 = ($4 == "N/A" ? -1 : $4) } 1' OFS=, test.csv
  • We set the input and output field separators to , to preserve the delimiters in your csv file
  • We check the forth field if it is equal to "N/A" then we assign it the value -1 if not we retain the value as is.
  • 1 at the end prints your line with or without modified 4th column depending if our test was successful or not.
  • ($4=="N/A"?-1:$4) is a ternary operator that checks if the condition $4=="N/A" is true or not. If true ? then we assign -1 and if false : we keep the field as is.

Test run on sample file:

$ cat file
a,b,c,d,e,f
1,2,3,4,5,6
44,2,1,N/A,4,5
24,sdf,sdf,4,2,254,5
a,f,f,N/A,f,4


$ awk -F, '{ $4 = ($4 == "N/A" ? -1 : $4) } 1' OFS=, file
a,b,c,d,e,f
1,2,3,4,5,6
44,2,1,-1,4,5
24,sdf,sdf,4,2,254,5
a,f,f,-1,f,4

Upvotes: 20

Jotne
Jotne

Reputation: 41460

Here is another awk (using example data from jaypal)

awk -F, '$4=="N/A" {$4=-1}1' OFS=, file
a,b,c,d,e,f
1,2,3,4,5,6
44,2,1,-1,4,5
24,sdf,sdf,4,2,254,5
a,f,f,-1,f,4

Upvotes: 4

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