Shell编程—【01】shell中常用的字符串操作

╰半夏微凉° 2021-09-12 07:56 366阅读 0赞

# Shell编程系列 [https://www.jianshu.com/nb/37140890][https_www.jianshu.com_nb_37140890] #

## 计算字符串长度 ##

*  $\{\#string\}
 *  expr length "$string"

v1="i love you"
    len=`expr length "$v1"`
    echo len

## 获取子串中字符在字符串中的位置 ##

*  expr index "![string" "][string_]subString"

v1="i love you"
    v2="ou"
    subIndex=`expr index "${v1}" "${v2}"`
    echo $subIndex
    # 4
    
    # 注意： 他其实是找子串中每个字符的其实位置，返回最前面的那个

## 获取子串从头开始匹配的长度 ##

*  expr match "![string" "][string_]substr"

v1="i love you"
    v2="ou"
    v3="i love"
    v4="i losadf"
    v5="i lov.*"
    subLen1=`expr match "$v1" "$v2"`
    subLen2=`expr match "$v1" "$v3"`
    subLen3=`expr match "$v1" "$v4"`
    subLen4=`expr match "$v1" "$v5"`
    echo $subLen1 $subLen2 $subLen3 $subLen4
    # 0 6 0 10

## 抽取子串 ##

# 0123456789
    # iloveyou.
    v1="iloveyou."
    # 从第零位开=始
    echo ${v1:0}
    # iloveyou.
    
    # 从第三位开始
    echo ${v1:3}
    # veyou.
    
    # 从右边开始匹配 倒数第三个开始 注意冒号后面有空格 从右边-1开始数
    echo ${v1: -3}
    # ou.
    
    echo ${v1: -3:1}
    # o
    
    # 从左边开始匹配  
    echo ${v1:(-3)}
    # ou.
    
    # 从第2位开始 截取3个
    expr substr "$v1" 2 3
    # lov
    
    # 注意expr 索引从1开始 ${}是从0开始

## 练习题 ##

给定一个字符串变量  
string=“You are an ugly boy! I'm a handsome boy!”  
要求启动脚本后  
1.输入1 打印字符串长度  
2.输入2 删除ugly 把 an 变成 a  
3.输入3 替换 'm 为 “ am” .  
4.输入4 替换 ! 为 .

#!/bin/bash
    
    string="You are an ugly boy! I'm a handsome boy!"
    
    function print_tips
    {
        echo "********************************"
        echo "1.输入1 打印字符串长度."
        echo "2.输入2 删除ugly 把 an 变成 a"
        echo "3.输入3 替换 'm 为 “ am” ."
        echo "4.输入4 替换 ! 为 ."
        echo "********************************"
    }
    function len_of_string
    {
        echo "${#string}"
    }
    
    function del_ugly_and_change_an_to_a
    {
        str="${string/ ugly/}"
        echo "${str/an/a}"
    }
    
    function replace_m_am
    {
        echo "${string//\'m/ am}"
    }
    
    function replace_exclamation_mark_to_dot
    {
        echo "${string//!/.}"
    }
    
    while true
    do
        echo "「string = ${string} 」"
        echo
        print_tips
        read -p "Please input your choice (1|2|3|4|q)" choice
    
        case $choice in
            1)
                len_of_string
                ;;
            2)
                del_ugly_and_change_an_to_a
                ;;
            3)
                replace_m_am
                ;;
            4)
                replace_exclamation_mark_to_dot
                ;;
            q|Q
                exit
                ;;
            *)
                echo "Error, Input only in (1|2|3|4|q)"
                ;;
        esac
    done

[https_www.jianshu.com_nb_37140890]: https://www.jianshu.com/nb/37140890
[string_]: https://math.jianshu.com/math?formula=string%22%20%22