How can I embed arguments in an awk script? - scripting

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