Bash Examples

Matt Danger — Sun, 23 Nov 2008 23:35:14 +0000

A while ago a friend was taking an entry level Unix programming class and asked me to help him study. I came up with some sample problems for him. Here are my solutions:

The first is a program that will allow a user to input as many numbers as the user wants (999 as the choice that ends the user input). The program will then output the highest number, the lowest number, the sum of all the numbers, and the average number.

#!/bin/bash
COUNT=0
echo -n "Enter a number (999 to quit): "
 
while read NUM; do
  # Set initials
  if [ $COUNT -eq 0 ]; then
    HIGHEST=$NUM
    LOWEST=$NUM
    SUM=$NUM
  fi
 
  # If 999 is entered, break out
  if [ $NUM -eq 999 ]; then
    break
  else
    # See if inputted number is the highest number
    if [ $NUM -gt $HIGHEST ]; then
      HIGHEST=$NUM
    fi
 
    # See if inputted number is the lowest number
    if [ $NUM -lt $LOWEST ]; then
      LOWEST=$NUM;
    fi
 
    # Calculate sum
    SUM=$(($SUM+$NUM))
 
    echo -n "Enter another number (999 to quit): "
  fi
 
  COUNT=$(($COUNT+1))
done
 
AVERAGE=$(($SUM/$COUNT))
echo "Highest number: $HIGHEST"
echo "Lowest number: $LOWEST"
echo "Sum of the numbers: $SUM"
echo "Average of the numbers: $AVERAGE"

The second program is a number guessing game. The computer picks a number from 0-60 then allows the user to guess at the number until the user gets it right. The program gives the user a hint on whether they should guess a higher or lower number.

#!/bin/bash 
RAN=$((RANDOM%60))
COUNTER=1
echo -n "I've guessed a number between 0-60, what is it? "
 
while read GUESS; do
 
  if [ $GUESS -eq $RAN ]; then
    break;
  else
    echo
    if [ $GUESS -lt $RAN ]; then
      echo -n "Nope, try a higher number: "
    else
      echo -n "Nope, try a lower number: "
    fi	
  fi
  COUNTER=$((COUNTER+1))
 
done
 
echo
echo "Yep, good job! It took you $COUNTER tries to guess correctly."

The third program allows a user to type in a number, then the program will either count up to the number provided by the user or count down from that number. In addition, a menu lets the user choose which counter they wish to use. In both cases that counter will either count down to 0, or start counting from 0.

#!/bin/bash 
echo -n "Enter a number: "; read NUM
echo -n "Enter U to count up to $NUM and D to count down to 0: "; read CHOICE
 
case $CHOICE in
  'u'|'U') 
    COUNTER=0
    while [ $COUNTER -le $NUM ]; do
      echo $COUNTER
      COUNTER=$(($COUNTER+1))
    done ;;
  'd'|'D')
    while [ $NUM -ge 0 ]; do
      echo $NUM;
      NUM=$(($NUM-1))
    done ;;
  *) echo "Error: You entered an invalid argument."
esac

The last program asks the user if they want to add, subtract, multiply or divide two user inputted numbers. Then the program outputs the sum of number 1 and number 2, the difference of number 1 and number 2, the product of number 1 and number 2, and the quotient of number 1 and number 2

This program will run until the user wants to quit. Also, if the user puts in a 0 as the second number, we let the user know that if they choose divide that a division by zero error will occur.

#!/bin/bash
while true; do
  echo "Please enter two numbers (type 'q' to quit): "
  echo -n "Number 1: "
  read NUM1
  if [ $NUM1 == "q" ]; then exit; fi
  echo -n "Number 2: "
  read NUM2
  echo -n "Enter (a) to add, (s) to subtract, (m) to multiply, or (d) to divide these numbers: "
  read OPERATION
 
  case $OPERATION in
    a) echo "The sum of $NUM1 and $NUM2 is: $(($NUM1+$NUM2))" ;;
    s) echo "The difference of $NUM1 and $NUM2 is: $(($NUM1-$NUM2))";;
    m) echo "The product of $NUM1 and $NUM2 is: $(($NUM1*$NUM2))" ;;
    d) if [ $NUM2 -eq 0 ]; then
        echo "You can't divide by 0, a division by zero error will occur."
      else 			
	    echo "The quotient of $NUM1 and $NUM2 is: $(($NUM1/$NUM2))"
      fi ;;
  esac
done

Matt [Danger] » Bash

Bash Examples