Displaying chess board on the screen

Small Chess Board

#!/bin/bash
# SCRIPT  : smallchessboard.sh
# PURPOSE : Prints small chess board on the screen.

clear
for (( i=1 ; i<=8 ; i++ ))
do

  for (( j=1 ; j<=8 ; j++ ))
  do

    if [ `expr $(($i+$j)) % 2` -eq 0 ]
    then
        echo -e -n "\033[47m  "         # White background
    else
        echo -e -n "\033[40m  "         # Black background
    fi

  done
  echo                                  # move to next line

done

echo -e "\033[0m"                       # Restores color settings.


OUTPUT:


Big Chess Board

#!/bin/bash
# SCRIPT  : bigchessboard.sh
# PURPOSE : Prints big chess board on the screen.

clear
a=4

for (( i=1 ; i<=8; i++ ))
do

   for (( j=1 ;j<=2; j++ ))            # prints same line twice
   do
      tput cup $a 15                   # moves cursor to LINE COLUMN

     for (( k=1 ; k<=8; k++ ))
     do

        c=`expr $((i+k)) %  2`

        if [ $c -eq 0 ]
        then
             echo -e -n "\033[40m    "   # Black background
        else
             echo -e -n "\033[47m    "   # White background
        fi

      done
      let a=a+1

    done

done

echo -e "\033[0m"                         # Restores color settings
read key                                  # Waits for enter


OUTPUT:

How can get nth line from a file

1. time head -5 emp.lst tail -1
   It has taken time for execution is
   real 0m0.004s
   user 0m0.001s
   sys 0m0.001s
   or
2. awk 'NR==5' emp.lst
   It has taken time for execution is
   real 0m0.003s
   user 0m0.000s
   sys 0m0.002s
   or
3. sed -n '5p' emp.lst
   It has taken time for execution is
   real 0m0.001s
   user 0m0.000s
   sys 0m0.001s
   or
4. using some cute trick we can get this with cut command
   cut -d “
   “ -f 5 emp.lst
   # after -d press enter ,it means delimiter is newline
   It has taken time for execution is
   real 0m0.001s
   user 0m0.000s
   sys 0m0.001s
   
   Analysis: comparing above commands 'head' command taken maximum time
   because it pipes the output to tail command. piping consumes some
   time.
   Next “awk” command has taken greater time ,because 'awk' not only
   a command, it is a programing language too.

When not to use shell scripts

· Resource-intensive tasks, especially where speed is a factor (sorting, hashing,
etc.)Procedures involving heavy-duty math operations, especially floating
point arithmetic, arbitraryprecision calculations, or complex numbers
(use C++ or FORTRAN instead)

· Cross-platform portability required (use C or Java instead) Complex applications, where structured programming is a necessity (need type-checking of variables, function prototypes, etc.)

· Project consists of subcomponents with interlocking dependencies Extensive file operations required (Bash is limited to serial file access, and that only in a particularly clumsy and inefficient line-by-line fashion)

· Need native support for multi-dimensional arrays
· Need data structures, such as linked lists or trees
· Need to generate or manipulate graphics or GUIs
· Need direct access to system hardware
· Need port or socket I/O
· Need to use libraries or interface with legacy code