Question

I am struggling with this awk code which should emulate the tail command

num=$1;
{
    vect[NR]=$0;
    
}
END{
    for(i=NR-num;i<=NR;i++)
            print vect[$i]
}

So what I’m trying to achieve here is an tail command emulated by awk/
For example consider cat somefile | awk -f tail.awk 10
should print the last 10 lines of a text file, any suggestions?

Answer 1

for(i=NR-num;i<=NR;i++)
    print vect[$i]

$ indicates a positional parameter. Use just plain i:

for(i=NR-num;i<=NR;i++)
    print vect[i]

The full code that worked for me is:

#!/usr/bin/awk -f
BEGIN{
        num=ARGV[1];
        # Make that arg empty so awk doesn't interpret it as a file name.
        ARGV[1] = "";
}
{
        vect[NR]=$0;
}
END{
        for(i=NR-num;i<=NR;i++)
                print vect[i]
}

You should probably add some code to the END to handle the case when NR < num.