Tutorial

像其他编程语言一样,shell可能具有函数。函数是实现一组命令和操作的子例程。这对于重复任务很有用。

# basic construct
function_name {
  command...
}

简单地通过写函数名称来调用它们。函数调用等效于命令。通过在函数名称后面指定参数,可以将参数传递给函数。函数中的第一个参数称为$ 1,第二个参数称为$ 2等。

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

在本练习中,您将需要编写一个称为ENGLISH_CALC的函数,该函数可以处理以下语句:

“ 3加5”,“ 5减1”或“ 4乘6”,并将结果分别打印为:“ 3 + 5 = 8”,“ 5-1 = 4”或“ 4 * 6 = 24”。

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

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