CODEWITHSUNDEEP
bashawkscripting
MirrG
MirrG

Reputation: 406

Awk script, incorrect response of "if" statement

I want to ask for help regarding a following problem:

I have two files, file 1:

1 apples
2 bananas
3 orange
4 prunes

and file 2:

1 oranges
2 apples
3 nuts

I need to extract from the file2 all the lines that doesn't match file1 (i.e "3 nuts"). I wrote an awk script:

#!/bin/awk -f 
BEGIN {
   while (getline <hdr>0) {
     a[i++]=$2;
   }
   close (hdr);
}
{ for (i in a) {
    if (a[i]!=$2) {
      print a[i];
    }
  }
}

My command line: 

awk -v hdr=file2 -f script_name file1

But the result that I got is just the content of the file2 several times. What the problem might it be?

Upvotes: 0

Views: 67

Answers (1)

karakfa
karakfa

Reputation: 67467

there are many things wrong with your code (even with the input files). Assuming the line numbers are part of your input you can try this

$ join -v2 -12 -22 -o2.1,2.2 <(sort -k2 file1) <(sort -k2 file2)

which will return

3 nuts
1 oranges

if you change "orange" to "oranges" in your first file you will only get the nuts.

A similar functionality awk script will be

$ awk 'NR==FNR{a[$2]=$0; next} 
       $2 in a{delete a[$2]} 
           END{for(k in a) print a[k]}' file2 file1

3 nuts
1 oranges

note file2 is provided first.

It will be simpler however, the other way around

$ awk 'NR==FNR{a[$2]; next} !($2 in a)' file1 file2

1 oranges
3 nuts

note that file1 is provided first.

Upvotes: 3

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