Cdtjkyj

[GNU awk v4.2.1 on Archlinux]

Suppressing awk's default print action to stdout from cli is easy and well documented on UL, e.g. here. Doing so from a script gives me headaches. Here's the toy script:

#!/usr/bin/awk -f

BEGIN {FS=","} 

FNR > 1          # skip header

{   

    if ( $1 == $2 ) {

        if ( NR == 4 ) {

            printf("*** Print NR=4 ok. n")

        } else {

            print > "/dev/null"  # print nothing

        }

    } else {

        printf("=== Fields 1 and 2 not equal (NR=%s). n",NR)

    }

}

and toy data:

col1 col2

1,3

2,2

aa,aa

3.01,-353.01

4.1,4.1

101,101

hello, hello

asd,koi0

along with expected / desired output:

=== Fields 1 and 2 not equal (NR=2). 

*** Print NR=4 ok. 

=== Fields 1 and 2 not equal (NR=5).

=== Fields 1 and 2 not equal (NR=8).

=== Fields 1 and 2 not equal (NR=9).

Instead I get:

=== Fields 1 and 2 not equal (NR=1). 

1,3

=== Fields 1 and 2 not equal (NR=2). 

2,2

aa,aa

*** Print NR=4 ok. 

3.01,-353.01

=== Fields 1 and 2 not equal (NR=5). 

4.1,4.1

101,101

hello, hello

=== Fields 1 and 2 not equal (NR=8). 

asd,koi0

=== Fields 1 and 2 not equal (NR=9). 

To suppress output to stdout, I tried using:
getline, {}, next, printf("") and even the outlandish ORS=""; print ""; ORS="n" instead of print > "/dev/null". I am obviously doing something very wrong in that frigging script and can not find what ...

The only error is

FNR > 1          # skip header

{ 

which should be

FNR > 1 {        # skip header

A code block with a condition must start on the same line as the condition.

What your original script actually does is first

FNR > 1

This prints all lines from line two onwards (the default action when a condition does not have an associated code block is to print the current record if the condition is true, as if the block had been { print }).

Then it applies the block following that to each line (since that block does not have an associated condition).

This is not a peculiarity of GNU awk. All awk implementations should act like this.

As for the other bits of the script:

    } else {

        print > "/dev/null"  # print nothing

    }

This could be deleted, leaving

#!/usr/bin/awk -f



BEGIN { FS = "," } 



FNR > 1 {   

    if ( $1 == $2 ) {

        if ( NR == 4 )

            printf("*** Print NR=4 ok.n")

    } else

        printf("=== Fields 1 and 2 not equal (NR=%s).n", NR)

}

or,

#!/usr/bin/awk -f



BEGIN { FS = "," } 



FNR == 1 { next }



$1 == $2 && NR == 4 { printf("*** Print NR=4 ok.n") }

$1 != $2            { printf("=== Fields 1 and 2 not equal (NR=%s).n", NR) }