Shell 编程(一)：Shell 变量的高级用法（一）

#!/bin/bash
# var1 = I love you,Do you love me
var1="I love you,Do you love me";
echo "var1 = ${var1}";
# ${变量名#匹配规则} var2 = e you,Do you love me
var2=${var1#*ov}
echo "var2 = ${var2}";
# ${变量名##匹配规则} var3 = e me
var3=${var1##*ov}
echo "var3 = ${var3}";
# ${变量名%匹配规则} var4 = I love you,Do you l
var4=${var1%ov*}
echo "var4 = ${var4}";
# ${变量名%%匹配规则} var5 = I l
var5=${var1%%ov*}
echo "var5 = ${var5}";
# ${变量名/旧字符串/新字符串} var6 = I like you,Do you love me
var6=${var1/love/like}
echo "var6 = ${var6}";
# ${变量名//旧字符串/新字符串} var7 = I like you,Do you like me
var7=${var1//love/like}
echo "var7 = ${var7}";
#!/bin/bash

#!/bin/bash
# 获取字符串长度
var1="Hello World"
echo "var1 = $var1"
len=${#var1}
echo "var1 len = $len"
# 通过expr获取
len=`expr length "$var1"`
echo "var1 len = $len"
# 获取字符索引位置
index=`expr index "$var1" rld`
echo "rld index = $index"
index=`expr index "$var1" a1d`
echo "a1d index = $index"
#获取子串长度(tips:匹配规则是从头开始匹配中间匹配无效)
sub_len=`expr match "$var1" rld`
echo "rld sub_len = $sub_len"
# 从 Hello 开始匹配则可成功
sub_len=`expr match "$var1" Hello`
echo "Hello sub_len = $sub_len"
# 抽取字符串中的子串
var2="redis mysql pgsql sqlserver"
echo "var2 = $var2"
# 从 var2 第 10 位开始提取子串
substr1=${var2:10}
echo "substr1 = $substr1"
# 从 var2 第 10 位开始提取长度为 5 的子串
substr2=${var2:10:5}
echo "substr2 = $substr2"
# 从 var2 的右边第 5 开始提取子串
substr3=${var2:-5}
echo "substr3 = $substr3"
substr4=${var2:(-5)}
echo "substr4 = $substr4"
# 从 var2 的右边第 5 开始提取长度为 5 的子串
substr5=${var2:-5:5}
echo "substr5 = $substr5"
# 从 5 开始,匹配长度为 10(tips:使用expr，索引计数是从1开始计算;使用${string:position}， 索引计数是从0开)
substr6=`expr substr "$var2" 5 10`
echo "substr6 = $substr6"

var1 = Hello World
var1 len = 11
var1 len = 11
rld index = 3
a1d index = 11
rld sub_len = 0
Hello sub_len = 5
var2 = redis mysql pgsql sqlserver
substr1 = l pgsql sqlserver
substr2 = l pgs
substr3 = redis mysql pgsql sqlserver
substr4 = erver
substr5 = redis mysql pgsql sqlserver
substr6 = s mysql pg

#!/bin/bash
string="Bigdata process framework is Hadoop , Hadoop is an open source project"
# 打印文字
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 "-----------------------------"
}
# 打印 string 长度
function len_of_string {
  echo ${#string}
}
# 删除字符串中所有的 Hadoop
function del_hadoop {
  echo ${string//Hadoop/}
}
# 替换第一个 Hadoop 为 Mapreduce
function rep_hadoop_mapreduce_first {
  echo ${string/Hadoop/mapreduce}
}
# 替换全部 Hadoop 为 Mapreduce
function rep_hadoop_mapreduce_all {
  echo ${string//Hadoop/mapreduce}
}
# 主程序
while true; do
  echo "[string=$string]"
  print_tips
  read -p "Pls input you 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
  echo "-----------------------------"
done