shell 中数组的基本操作

数组（Array）是一个由若干同类型变量组成的集合，引用这些变量时可用同一名字。数组均由连续的存储单元组成，最低地址对应于数组的第一个元素，最高地址对应于最后一个元素。bash Shell只支持一维数组，数组从0开始标号，以array[x]表示数组元素，那么，array[0]就表示array数组的第1个元素、array[1]表示array数组的第2个元素、array[x]表示array数组的第x+1个元素。
bash Shell取得数组值（即引用一个数组元素）的命令格式是：
${array[x]} #引用array数组标号为x的值，$符号后面的大括号必不可少

定义

declare -a city    # city为数组名 

赋值

#!/bin/bash
city[0]=Nanjing
city[1]=Beijing
city[9]=Melbourne
city[15]=NewYork

echo "city[0]=${city[0]}"
echo "city[1]=${city[1]}"
echo "city[9]=${city[9]}"
echo "city[15]=${city[15]}"
echo "city[2]=${city[2]}"
echo "city[10]=${city[10]}"

还可以用小括号将一组值赋给数组

city=(Nanjing Beijing Melbourne NewYork)
city=(Nanjing [10]=Atlanta Massachusetts Marseilles)
city=([2]=Nanjing [10]=Atlanta [1]=Massachusetts [5]=Marseilles)

array[@]和array[*]都表示了array数组的所有元素

for i in ${city[@]}                #将@替换为*亦可
do
       echo $i
done

操作

数组字符串所有操作都是针对所有数组元素逐个进行的

切片

city=(Nanjing Atlanta Massachusetts Marseilles)
echo "Extracting Substring"
echo ${city[*]:0}
echo ${city[*]:1}
echo ${city[*]:3}
echo ${city[*]:0:2}  从编号为0 的开始 ，长度为2
echo

剔除

echo "Removing Substring"
echo ${city[*]#M*a}   //按最小长度删除
echo ${city[*]##M*a} //按最大长度删除
echo
echo "Replcing Substring"
echo ${city[*]/M*s/Year}
echo ${city[*]//M*s/Year

用read命令从stdin读取一系列的值
read -a array可以将读到的值存储到array数组

echo "What city have you been arrived?"
echo "The input should be separated from each other by a SPACE"
read -a arrivedcity
echo
for i in "${arrivedcity[@]}"
do
  echo "$i"
done

删除元素

echo "The length of this array is ${#arrivedcity[@]}."
echo "Executing UNSET operation........."
unset arrivedcity[1]   //删除第2个城市
echo "The length of this array is ${#arrivedcity[@]}."
echo "Executing UNSET operation........."
unset arrivedcity   //删除所有的城市
echo "The length of this array is ${#arrivedcity[@]}."

数组连接

将多个数组合并到一个数组

＃定义并赋值
city=(Beijing Nanjing Shanghai)
person=(Cai [5]=Wu Tang)

方法一

declare -a combine     //声明一个数组，其名为combine 
combine=(${city[@]} ${person[@]})
#combine=${city[@]}${person[@]}
element_count=${#combine[@]} //获取数组长度
index=0
while [ "$index" -lt "$element_count" ]
do
   echo "Element[$index]=${combine[$index]}"
   let "index=$index+1"
done
echo
unset combine    //删除数组

方法二

combine[0]=${city[@]}
combine[1]=${person[@]}
element_count=${#combine[@]}
index=0
while [ "$index" -lt "$element_count" ]
do
   echo "Element[$index]=${combine[$index]}"
   let "index=$index+1"
done
echo

方法三

declare -a subcombine=${combine[1]}      //声明一个数组，其值为${combine[1]} 
element_count=${#subcombine[@]}
index=0
while [ "$index" -lt "$element_count" ]
do
   echo "Element[$index]=${subcombine[$index]}"
   let "index=$index+1"
done