How can I embed arguments in an awk script?

Question

This is the evolution of these two questions, here, and here.

For mine own learning, I'm trying to accomplish two (more) things with the code below:

1. Instead of invoking my script with # myscript -F "," file_to_process, how can I fold in the '-F ","' part into the script itself?

2. How can I initialize a variable, so that I only assign a value once (ignoring subsequent matches? You can see from the script that I parse seconds and micro seconds in each rule, I'd like to keep the first assignment of sec around so I could subtract it from subsequent matches in the printf() statement.

   #!/usr/bin/awk -f
   /DIAG:/  {
       lbl = $3;
       sec = $5;
       usec = $6;
       /Test-S/ {
           stgt = $7;
           s1  = $30;
           s2  = $31;
       }
       /Test-A/ {
           atgt = $7;
           a = $8;
       }
       /Test-H/ {
           htgt = $7;
           h = $8;
       }
       /Test-C/ {
           ctgt = $7;
           c = $8;
       }
   }
   /WARN:/ {
       sec = $4;
       usec = $5;
       m1 = $2;
       m2 = $3
   }
   {
    printf("%16s,%17d.%06d,%7.2f,%7.2f,%7.2f,%7.2f,%7.2f,%7.2f,%7.2f,%7.2f,%7.2f,%5d,%5d\n", lbl, sec, usec, stgt, s1, s2, atgt, a, htgt, h, ctgt, c, m1, m2)
   }
   

Answer 1

Use a BEGIN clause:

BEGIN { FS = ","
    var1 = "text"
    var2 = 3
    etc.
}

This is run before the line-processing statements. FS is the field separator.

If you want to parse a value and keep it, it depends on whether you want only the first one or you want each previous one.

To keep the first one:

FNR==1 {
    keep=$1
}

To keep the previous one:

BEGIN {
    prevone = "initial value"
}

/regex/ {
    do stuff with $1
    do stuff with prevone
    prevone = $1
}