Concatenate bash sources once to create standalone file

concat-bash-sources.awk

#!/usr/bin/env awk
# usage 
# echo "main.sh" | awk -v header='# HEADER COMMENT' -v footer='# FOOTER COMMENT' -f concat-bash-sources.awk
            
function read_file_content(file) {
    while ((getline line < file) > 0) {
        if ( line ~ /^source / ) {
            print parse_bash_source(line)
        # remove comments and hashbangs
        } else if ( line !~ /^#/ ) {
            print line
        }
    }
}

function match_source_path(line) {
    return substr(line, 9, length(line) - 9)
}

function parse_bash_source(line) {
    src = match_source_path(line)
    if (cached[src] != 1) {
        read_file_content(src)
    }
    cached[src] = 1
}

BEGIN {
    print "#!/usr/bin/env bash"
    if (header) {
      print header
    }
}
{
    read_file_content($0)
}
END {
    if (footer) {
      print footer
    }
}