gawk '
function menu(){
        printf "\n<< Grep Simulation Script >>\n"
        print "------------------------------"
        print "1.(n) Grep -n"
        print "2.(v) Grep -v"
        print "3.(i) Grep -i"
        print "4.(w) Grep -w"
        print "5.(f) Grep -f"
        print "6. (E)xit"

}
function exists(file,      dummy, ret) {
   ret=0;
   if ( (getline dummy < file) >=0 ) {ret = 1; close(file)};
   return ret;
}

function grep(filename,text,linenum,invert,whole ){
   if ( exists(filename) ){
        linecount=0
        while ( (getline line < filename ) > 0 ) {
            linecount++
            if ( invert && line !~ text){
                print line
            }else if ( whole ){
                z=split(line, L, " ")
                for(j=1;j<=z;j++){
                    gsub(/^ +| +$/,"",L[i])
                    if ( L[j] == text ){
                        print line
                    }
                }
            } else if ( line ~ text) {
                if ( linenum )
                    print linecount": "line
                else { print line }
            }
        }
   }else{
        print "File: "filename" does not exists"
        return 1
   }

}
BEGIN{
    while(1){
        IGNORECASE=0
        linenum=0
        invert=0
        menu()
        printf "Your choice: "
        getline choice <"-"
        if ( choice == 1 ){
            linenum=1
        }else if ( choice == 2){
            invert=1
        }else if ( choice == 3 ){
            IGNORECASE=1
        }else if ( choice == 4){
            whole=1
        }else if ( choice == 5) {
            print "Not implemented"
            continue
        }else if ( choice == 6) {
            print "Exiting...."
            exit
        }
        printf "Enter text to search: "
        getline text <"-"
        printf "Enter filename: "
        getline file < "-"
        grep(file,text,linenum,invert,whole)
    }
}'