Tutorial

Like other programming languages, the shell may have functions. A function is a subroutine that implements a set of commands and operations. It is useful for repeated tasks.

# basic construct
function_name {
  command...
}

Functions are called simply by writing their names. A function call is equivalent to a command. Parameters may be passed to a function, by specifying them after the function name. The first parameter is referred to in the function as $1, the second as $2 etc.

function function_B {
  echo "Function B."
}
function function_A {
  echo "$1"
}
function adder {
  echo "$(($1 + $2))"
}

# FUNCTION CALLS
# Pass parameter to function A
function_A "Function A."     # Function A.
function_B                   # Function B.
# Pass two parameters to function adder
adder 12 56                  # 68

Exercise

In this exercise, you will need to write a function called ENGLISH_CALC which can process sentences such as:

‘3 plus 5’, ‘5 minus 1’ or ‘4 times 6’ and print the results as: ‘3 + 5 = 8’, ‘5 - 1 = 4’ or ‘4 * 6 = 24’ respectively.

Tutorial Code

#!/bin/bash
# enter your function code here

# testing code
ENGLISH_CALC 3 plus 5
ENGLISH_CALC 5 minus 1
ENGLISH_CALC 4 times 6

Expected Output

3 + 5 = 8
5 - 1 = 4
4 * 6 = 24

Show Solution

#!/bin/bash
# enter your function code here

function ENGLISH_CALC {
a=$1
  b=$3
  signn=$2
  if [ $signn == "plus" ]; then
    echo "$a + $b = $(($a+$b))"
  elif [ $signn == "minus" ]; then
    echo "$a - $b = $(($a-$b))"
  elif [ $signn == "times" ]; then
    echo "$a _ $b = $(($a_$b))"
fi
}

# testing code

ENGLISH_CALC 3 plus 5
ENGLISH_CALC 5 minus 1
ENGLISH_CALC 4 times 6