You are right agama. It is not really clear.

I try with a precise example:

I need to convert every second line of the input starting from the first letter, then starting from the second letter, then the third, ..., and finally starting from the letter before the last one (according to the conversion table in the BEGIN section).

input:

Code:

%line1
abcdef
%line2
...

in order to get this ouput:

Code:

line1|135   # starting from the first letter (i.e. "abcdef")
line1|24X   # starting from the second letter (i.e. "bcdef")
line1|35     # starting from the third letter (i.e. "cdef")
line1|4X     # starting from the fourth letter (i.e. "def")
line1|5       # starting from the fifth letter (i.e. "ef")
line2|...

I wanted to do that with 2 different approaches, just to be familiar with awk user-defined function and the function getline:

1) using an increment in a function called "convert(letter)" with only one argument, and use the result as a variable that I could use in the rest of the script.
This is the topic I posted in a different thread:https://www.unix.com/unix-dummies-que...program-2.html

2) not using an increment in the function called "convert(letter, start)" with two arguments (the string to convert + the position to start), and redirect the results from the script to an output file. From this file I wanted to use the getline function to redirect it from the script and keep processing it.
This is the topic of this thread.

But it appeared that none of these strategies work !!!

For the purpose of this thread I focused on using getline function (2nd strategy).
I tried:

Code:

BEGIN {RS="%"; ORS="\n"; OFS="|"; conv["ab"]="1"; conv["bc"]="2"; conv["cd"]="3"; conv["de"]="4"; conv["ef"]="5"}

     
    function convert(letter, start){
        number = ""
        ss = substr(letter, start, 2) 
        while( ss != "" ){
            number = number (ss in conv ? conv[ss] : "X")
            start = start + 2;
            ss = substr(letter, start, 2)
        }
        return number
    }


NR==1{next}
	
NR>1{
            sub("\n","|",$0)

           { 
                l = length($2)
                for(i=1; i<=(l-1);  i++){
                    print convert($2, i) > "track.txt"     # redirect output to a file here
                }
                close("track.txt")                              # according to your suggestion
           }
}

{
    RS="\n"
    while(0< (getline < "track.test")){
        print $2}
}

The output I obtain with this code is messy (a mix between the original input with no FS, RS...)