详解shell 变量的高级用法示例

variable_1="I love you, Do you love me"
echo $variable_1
variable_2=${variable_1#*ov}
echo $variable_2

varible_3=${variable_1##*ov}
echo $varible_3

echo $PATH
var6=${PATH/bin/BIN}
echo $var6

var7=${PATH//bin/BIN}
echo $var7

var=${str-expr}

var="hello world"
len=${#var}
echo $len

var1="zhang biao"
len=`expr length "$var1"`
echo $len

var="quickstart is a app"
ind=`expr index "$var" start`
echo $ind

ind=`expr index "$var" uniq`
echo $ind

var="quickstart is a app"
sub_len=`expr match "$var1" app`
echo $sub_len

sub_len=`expr match "$var" quick*`
echo $sub_len

sub_len=`expr match "$var" quick.*`
echo $sub_len

var1="kafka hadoop yarn mapreduce"
sub_str1=${var1:10}
echo $sub_str1

sub_str2=${var1:10:5}
echo $sub_str2

sub_str3=${var1: -5}
echo $sub_str3

sub_str3=${var1:(-5)}
echo $sub_str3

sub_str3=${var1: -5:2}
echo $sub_str3

#!/bin/bash
#
 
string="Bigdata process framework is Hadoop,Hadoop is an open source project"
 
function print_tips
{
 echo "********************************************"
 echo "(1)打印string长度"
 echo "(2)删除字符串中所有的Hadoop"
 echo "(3)替换第一个Hadoop为Mapreduce"
 echo "(4)替换全部Hadoop为Mapreduce"
 echo "********************************************"
}
 
function len_of_string
{
 echo "${#string}"
}
 
function del_hadoop
{
 # 把hadoop替换为空
 echo "${string//Hadoop/}"
 
}
 
function rep_hadoop_mapreduce_first
{
 echo "${string/Hadoop/Mapreduce}"
}
 
function rep_hadoop_mapreduce_all
{
 echo "${string//Hadoop/Mapreduce}"
}

#!/bin/bash
#
 
string="Bigdata process framework is Hadoop,Hadoop is an open source project"
 
function print_tips
{
 echo "********************************************"
 echo "(1) 打印string长度"
 echo "(2) 删除字符串中所有的Hadoop"
 echo "(3) 替换第一个Hadoop为Mapreduce"
 echo "(4) 替换全部Hadoop为Mapreduce"
 echo "********************************************"
}
 
function len_of_string
{
 echo "${#string}"
}
 
function del_hadoop
{
 # 把hadoop替换为空
 echo "${string//Hadoop/}"
 
}
 
function rep_hadoop_mapreduce_first
{
 echo "${string/Hadoop/Mapreduce}"
}
 
function rep_hadoop_mapreduce_all
{
 echo "${string//Hadoop/Mapreduce}"
}
 
while true
do
 echo " 【string=$string】"
 echo
 print_tips
 read -p "Pls input your choice(1|2|3|4|q|Q):" choice
 
 case $choice in
  1)
   len_of_string
   ;;
  2)
   del_hadoop
   ;;
  3)
   rep_hadoop_mapreduce_first
   ;;
  4)
   rep_hadoop_mapreduce_all
   ;;
  q|Q)
   exit
   ;;
  *)
   echo "Error,input only in {1|2|3|4|q|Q}"
   ;;
 esac
done

cat /etc/passwd | cut -d ":" -f 1

#!/bin/bash
#
 
index=1
for user in `cat /etc/passwd | cut -d ":" -f 1`
do
 echo "this is $index user: $user"
 index=$(($index + 1))
done

echo "this is $(date +%Y) year"
echo "this is $(( $(date +%Y) + 1)) year"

echo "$((20+30))"

echo $((100+30))
echo $(( (100 + 30) / 13 ))
echo $(( $num1 + $num2 * 2))

num1=50
num2=70
echo "$((num1 + num2))"

echo $(date +%j)

echo "this year have passed $(date +%j) days"
echo "this year have passed $(($(date +%j) / 7)) weeks"

echo "there is $((365 - $(date +%j))) days before new year"
echo "there is $(((365 - $(date +%j)) / 7 )) weeks before new year"

#!/bin/bash
#
# grep -v 过滤掉 grep 进程
nginx_process_num=$(ps -ef|grep nginx|grep -v grep|wc -l)
 
if [ $nginx_process_num -eq 0 ];then
systemctl start nginx
fi

var2="hello python"
declare -r var2
var2="hello java"

num1=10
num2=$num1+20
echo $num2

declare -i num3
num3=$num1+90
echo $num3

declare -a array
array=("jones" "make" "kobe" "jordan")

echo ${array[@]}

echo ${array[1]}

echo ${#array[@]}

echo ${#array[0]}

declare -f
declare -F

array=("jones" "mike" "kobe" "jordan")
输出数组内容：
 echo ${array[@]} 输出全部内容
 echo ${array[1]} 输出下标索引为1的内容
 
获取数组长度：
 echo ${#array}  数组内元素个数
 echo ${#array[2]} 数组内下标索引为2的元素长度
 
给数组某个下标赋值：
 array[0]="lily"  给数组下标索引为1的元素赋值为lily
 array[20]="hanmeimei" 在数组尾部添加一个新元素
 
删除元素：
 unset array[2]  清空元素
 unset array  清空整个数组
 
分片访问：
 ${array[@]:1:4}  显示数组下标索引从1开始到3的3个元素
 
内容替换：
 ${array[@]/an/AN} 将数组中所有元素包含an的子串替换为AN
 
 
数组遍历：
 for v in ${array[@]}
 do
  echo $v
 done

#!/bin/bash
#
 
echo $num5

num5=30
declare -x num5