Shell编程学习笔记(二)-变量的高级用法

1.变量替换

example1:根据匹配规则删除变量部分内容 

example2:根据匹配规则替换变量部分内容

 

2.字符串处理

注意： ${}计算索引是从0开始 expr计算索引是从1开始。

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3.关于字符串的完整脚本实例

#!/bin/bash

string="Bigdata process framework is Hadoop,Hadoop is an open source project"

function tips_info
{
        echo "*********************************"
        echo "*** (1) 打印string长度"
        echo "*** (2) 在整个字符串中删除Hadoop"
        echo "*** (3) 替换第一个Hadoop为Mapreduce"
        echo "*** (4) 替换全部Hadoop为Mapreduce"
        echo "*********************************"
}

function print_len
{
        if [ -z "$string" ];then
                echo "Error,string is null"
                exit 1
        else
                echo "${#string}"
        fi
}
function del_hadoop
{
        if [ -z "$string" ];then
                echo "Error,string is null"
                exit 1
        else
                echo "${string//hadoop/}"
        fi
}

function rep_hadoop_mapreduce_first
{
        if [ -z "$string" ];then
                echo "Error,string is null"
                exit 1
        else
                echo "${string/Hadoop/Mapreduce}"
        fi
}
function rep_hadoop_mapreduce_all
{
        if [ -z "$string" ];then
                echo "Error,string is null"
                exit 1
        else
                echo "${string//Hadoop/Mapreduce}"
        fi
}

while true
do

echo "[string=\"$string\"]"
tips_info
read -p "please Switch a Choice: " choice

case "$choice" in
        1)
                echo
                echo "Length Of String is:`print_len`"
                echo
                continue
                ;;
        2)
                echo
                echo "删除Hadoop后的字符串为:`del_hadoop`"
                ;;
        3)
                echo
                echo "替换第一个Hadoop后的字符串为:`rep_hadoop_mapreduce_first`"                                        
                ;;
        4)
                echo
                echo "替换全部的Hadoop后的字符串为:`rep_hadoop_mapreduce_all`"
                ;;

        q|Q)
                exit 0
                ;;
        *)
                echo "error,unlegal input,legal input only in { 1|2|3|4|q|Q }"
                continue
                ;;
esac
done