Created Saturday 15 August 2020
ARGC, ARGV Argumant counter and array of argument values
FS Input field separator variable
OFS Output Field Separator Variable
RS Record Separator variable
ORS Output Record Separator Variable
NR Number of Records Variable
NF Number of Fields in a record
FILENAME Name of the current input file
FNR Number of Records relative to the current input file
RSTART Index of the substring matched
RLENGTH Length of the substring matched
IGNORECASE Non-zero or non-null makes comparisons case-insensitive