AWK - if not in array

Question

I have two files separated by tabs. Comparing files by the first field, I need to print the line where the field does not match. But the line to be printed is from the file (file1)

File1:

adu adu noun    singular    n/a n/a nominative
aduink  adu noun    plural  1pl n/a nominative
adum    adu noun    singular    1s  n/a nominative

File2:

adu adu noun    singular    n/a n/a nominative
aduink  adu noun    plural  1pl n/a nominative
xxadum  adu noun    singular    1s  n/a nominative

Desired output:

adum    adu noun    singular    1s  n/a nominative

What I'm thinking:

awk 'FNR==NR{a[$1]=$0;next} !($1 in a)' file1 file2

But I need to print, the line from file (file1) not from file (file2). And I can not change the order to process files

Your FNR==NR expression gets run on the first file listed after the awk script, in this case file1. That means that your subsequent expression, !($1 in a), is evaluated against lines in file2. If you want to store $1 of file2 in the array and then compare lines of file1 against the array, simply swap the order of the files on your awk command line. — ghoti
– ghoti, Commented Feb 26, 2016 at 12:38

Casimir et Hippolyte · Accepted Answer · 2016-02-26 17:14:30Z

2

I don't understand why you can't change the files order (that is more simple), but you with the same order, you can do that:

awk 'NR==FNR{ a[$1]=$0; next }
     { delete a[$1] }
     END{ for (x in a) print a[x] }' file1 file2

The idea is to delete all items at index $1 when the second file is processed. Then at the end, you only need to print the remaining items.

edited Feb 26, 2016 at 17:14

answered Feb 26, 2016 at 12:52

Casimir et Hippolyte

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Comments

sat · Accepted Answer · 2016-02-26 12:35:36Z

1

Why don't you interchange the files in the argument that you are passing to awk,

awk 'FNR==NR{a[$1]=$0;next} !($1 in a)' file2 file1
                                          |     |
                                         arg1  arg2

edited Feb 26, 2016 at 12:35

answered Feb 26, 2016 at 12:30

sat

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1 Comment

Ed Morton Over a year ago

No need for =$0, it's not used and just sucking up memory.

Ed Morton · Accepted Answer · 2016-02-26 16:40:42Z

1

If you can't change the file order when awk is called, just change it inside awk:

awk 'BEGIN{t=ARGV[1]; ARGV[1]=ARGV[2]; ARGV[2]=t} FNR==NR{a[$1];next} !($1 in a)' file1 file2

That way you don't have to store either file in memory.

answered Feb 26, 2016 at 16:40

Ed Morton

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Comments

karakfa · Accepted Answer · 2016-02-27 04:19:53Z

0

late to the party but here is a simpler way to do this

$ join -v1 file1 file2

adum adu noun singular 1s n/a nominative

that is, to suppress joined lines and print the unpaired lines from first file. By default join is by first field.

answered Feb 27, 2016 at 4:19

karakfa

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