myscript.awk

#!/usr/bin/gawk -f
#
# This script lists student statistics for MM2090
# during July-2019 semester.
# Run this as follows:
#
# cat RollList.csv | awk -f myscript.awk
#
# The BEGIN block is executed once before the lines are read and processed.
BEGIN{
    print "beginning...";
    c=0;
    mecount=0;
    mmcount=0;
    cecount=0;
    freshies=0;
    seniors=0;
    # This is a field separator to split the incoming line
    # into fields. Default separator is a blank space.
    FS=",";
}
{
# The main code block is executed once per each line read.
      c++;
      print $0;
      r=$1;
      n=$2;
      # This if loop checks if the roll number starts with ME
      if(r \~ /^ME/) mecount++;
      if(r \~ /^MM/) mmcount++;
      if(r \~ /^CE/) cecount++;
      # This if loop checks if the roll number has 19 in the third
      # and fourth positions
      if(r ~ /^..19/) freshies++;
      # This if loop checks if the roll number does not have 9 in
      # the fourth position
      if(r ~ /^..1[^9]/) seniors++;
      # Associative array with the roll number as index/key and
      # name of the student as value
      names[r]=n;
      # Associative array with the roll number as index/key and
      # email of the student as value
      # The function tolower() converts a string to lower case
      email[r]=tolower(r) "@smail.iitm.ac.in";
      # Associative array with the roll number as index/key and
      # a random number between 1 and 8 as value.
      # The function rand() outputs a random number between 0 and 1
      group[r] = int(1+rand()*8);
}
END{
# The END block is executed once after all the lines are read and processed.
      print c;
      print "...closing";
      print("Number of mech students: ", mecount);
      print("Number of meta students: ", mmcount);
      print("Number of civil students: ", cecount);
      print("Number of freshies: ", freshies);
      print("Number of seniors: ", seniors);
      print("-----------------------------------");
      # This for loop runs over all the keys of the associative
      # array called names
      for (r in names) {
          print(r, " : ", names[r], " : ", email[r], " : ", group[r]);
      }
      print("------------------------------------");
      print("Students in group 1 ");
      # This for loop runs over all the keys of the associative
      # array called email
      for (r in email) {
          # This if loop checks if the value of the associative
          # array for the key r has a value 1 meaning group 1
          if(group[r] == 1) print(r, " : ", names[r], " : ", email[r], " : ", group[r]);
      }
}