当前位置： 首页 > news >正文

仪表东莞网站建设关键字有哪些

news 2025/7/19 15:26:49
仪表东莞网站建设,关键字有哪些,南京做网站咨询南京乐识,网站规划文字说明概念 把复杂的命令执行过程，通过逻辑代码，组成一个脚本文件的方式就叫做shell脚本。 shebang #! /bin/bash #! /bin/perl #! /bin/python执行脚本的方式 source my_first.sh . my_first.shbash my_first.sh ./my_first.sh变量引用 ${var} 取出变量结果 …

概念

把复杂的命令执行过程，通过逻辑代码，组成一个脚本文件的方式就叫做shell脚本。

shebang

#! /bin/bash
#! /bin/perl
#! /bin/python

执行脚本的方式

source my_first.sh
. my_first.shbash my_first.sh
./my_first.sh

变量引用
${var} 取出变量结果
$() 在括号中执行命令，且拿到命令的执行结果
`` 在括号中执行命令，且拿到命令的执行结果
$var 取出变量结果
() 开启子shell执行命令

xiao123@xiao123:~/Downloads/shscripts$ echo "当前用户是：$(whoami)"
当前用户是：xiao123
xiao123@xiao123:~/Downloads/shscripts$ echo "当前用户是：`whoami`"
当前用户是：xiao123
xiao123@xiao123:~/Downloads/shscripts$ var=xiao123
xiao123@xiao123:~/Downloads/shscripts$ echo "当前用户是：${var}"
当前用户是：xiao123
xiao123@xiao123:~/Downloads/shscripts$ echo "当前用户是：$var"
当前用户是：xiao123
xiao123@xiao123:~/Downloads/shscripts$

数学计算

支持的运算符展示
数学计算1

Linux用于计算的命令展示
shell基础命令只支持整数，小数运算需要使用bc命令
运算命令

双小括号(())

用法
(())用法
演示：

xiao123@xiao123:~/Downloads/shscripts$ echo $((5<7))   #为True，1
1
xiao123@xiao123:~/Downloads/shscripts$ echo $((5>7))   #为Fase，0
0
xiao123@xiao123:~/Downloads/shscripts$

脚本开发

1.想好脚本的功能，作用，以及需求
2.转换为shell代码

开发一个，接收用户输入数字，且对运算符号判断，最终的出结果的一个计算脚本

  1. 接收用户输入
  2. 对用户输入的不是数字进行判断
  3. 对输入的运算符进行判断
  4. 最终进行结果计算，输出打印

代码

xiao123@xiao123:~/Downloads/shscripts$ cat ./calculation.sh
#! /bin/bashdo_usage() {printf "Please input an integer!!!\n"exit 1
}read -p "Please input first number: " firstif [ -n "`echo ${first}|sed 's/[0-9]//g'`" ];
thendo_usage
firead -p "Please input an operator: " operatorif [ ${operator} != '+' ] && [ ${operator} != '-' ] && [ ${operator} != '/' ] && [ ${operator} != '*' ];
thenecho "Please input [+/-/*//]!!!"exit 2
firead -p "Please input second number: " secondif [ -n "`echo ${second}|sed 's/[0-9]//g'`" ];
thendo_usage
fiecho "${first}${operator}${second}=" $((${first}${operator}${second}))
xiao123@xiao123:~/Downloads/shscripts$

运行结果

xiao123@xiao123:~/Downloads/shscripts$ ./calculation.sh
Please input first number: qew123
Please input an integer!!!
xiao123@xiao123:~/Downloads/shscripts$ ./calculation.sh
Please input first number: 123
Please input an operator: eeee
Please input [+/-/*//]!!!
xiao123@xiao123:~/Downloads/shscripts$ ./calculation.sh
Please input first number: 123
Please input an operator: +
Please input second number: 12
123+12= 135
xiao123@xiao123:~/Downloads/shscripts$

let命令运算

let命令的执行，效果等同于双小括号(())
但是，双小括号(())效率更高

#对比
xiao123@xiao123:~/Downloads/shscripts$ num=5
xiao123@xiao123:~/Downloads/shscripts$ num=num+5
xiao123@xiao123:~/Downloads/shscripts$ echo ${num}
num+5
xiao123@xiao123:~/Downloads/shscripts$ num=5+5
xiao123@xiao123:~/Downloads/shscripts$ echo ${num}
5+5
xiao123@xiao123:~/Downloads/shscripts$
#let命令
xiao123@xiao123:~/Downloads/shscripts$ num=5
xiao123@xiao123:~/Downloads/shscripts$ let num=num+5
xiao123@xiao123:~/Downloads/shscripts$ echo ${num}
10
xiao123@xiao123:~/Downloads/shscripts$ let num=5+5
xiao123@xiao123:~/Downloads/shscripts$ echo ${num}
10
xiao123@xiao123:~/Downloads/shscripts$

脚本开发，对于nginx运行状态检测

#! /bin/bashCheckUrl(){timeout=5fails=0success=0while truedowget --timeout=${timeout} --tries=1 http://www.baidu.com -q -o /dev/nullif [ $? -ne 0 ];thenlet fails=fails+1elselet success=success+1fiif [ ${success} -ge 1 ];thenecho "恭喜你，服务运行正常"exit 0fiif [ ${fails} -ge 2 ];thenecho "糟糕了，服务运行异常，请检查服务器状态"exit 2fidone
}CheckUrl# 运行结果
xiao123@xiao123:~/Downloads/shscripts$ ./let_test.sh
恭喜你，服务运行正常
xiao123@xiao123:~/Downloads/shscripts$

expr命令

简单的计算器执行命令。

xiao123@xiao123:~/Downloads/shscripts$ expr --help
Usage: expr EXPRESSIONor:  expr OPTION--help     display this help and exit--version  output version information and exitPrint the value of EXPRESSION to standard output.  A blank line below
separates increasing precedence groups.  EXPRESSION may be:ARG1 | ARG2       ARG1 if it is neither null nor 0, otherwise ARG2ARG1 & ARG2       ARG1 if neither argument is null or 0, otherwise 0ARG1 < ARG2       ARG1 is less than ARG2ARG1 <= ARG2      ARG1 is less than or equal to ARG2ARG1 = ARG2       ARG1 is equal to ARG2ARG1 != ARG2      ARG1 is unequal to ARG2ARG1 >= ARG2      ARG1 is greater than or equal to ARG2ARG1 > ARG2       ARG1 is greater than ARG2ARG1 + ARG2       arithmetic sum of ARG1 and ARG2ARG1 - ARG2       arithmetic difference of ARG1 and ARG2ARG1 * ARG2       arithmetic product of ARG1 and ARG2ARG1 / ARG2       arithmetic quotient of ARG1 divided by ARG2ARG1 % ARG2       arithmetic remainder of ARG1 divided by ARG2STRING : REGEXP   anchored pattern match of REGEXP in STRINGmatch STRING REGEXP        same as STRING : REGEXPsubstr STRING POS LENGTH   substring of STRING, POS counted from 1index STRING CHARS         index in STRING where any CHARS is found, or 0length STRING              length of STRING+ TOKEN                    interpret TOKEN as a string, even if it is akeyword like 'match' or an operator like '/'( EXPRESSION )             value of EXPRESSIONBeware that many operators need to be escaped or quoted for shells.
Comparisons are arithmetic if both ARGs are numbers, else lexicographical.
Pattern matches return the string matched between \( and \) or null; if
\( and \) are not used, they return the number of characters matched or 0.Exit status is 0 if EXPRESSION is neither null nor 0, 1 if EXPRESSION is null
or 0, 2 if EXPRESSION is syntactically invalid, and 3 if an error occurred.GNU coreutils online help: <https://www.gnu.org/software/coreutils/>
Report any translation bugs to <https://translationproject.org/team/>
Full documentation <https://www.gnu.org/software/coreutils/expr>
or available locally via: info '(coreutils) expr invocation'
xiao123@xiao123:~/Downloads/shscripts$

实践
运算

expr 命令并不是很好用，基于空格传输参数，但是在shell中一些元字符都是有特殊含义的。
xiao123@xiao123:~/Downloads/shscripts$ expr 5 \+ 3
8
xiao123@xiao123:~/Downloads/shscripts$ expr 5 \- 3
2
xiao123@xiao123:~/Downloads/shscripts$ expr 5 \* 3
15
xiao123@xiao123:~/Downloads/shscripts$ expr 5 \/ 3
1
xiao123@xiao123:~/Downloads/shscripts$

求长度

xiao123@xiao123:~/Downloads/shscripts$ expr length 123456789
9
xiao123@xiao123:~/Downloads/shscripts$

逻辑运算

xiao123@xiao123:~/Downloads/shscripts$ expr 5 \> 6
0
xiao123@xiao123:~/Downloads/shscripts$ expr 5 \< 6
1
xiao123@xiao123:~/Downloads/shscripts$

模式匹配
2个特殊符号：

  • : 冒号，计算字符串字符的数量，Yuchao 6个字符
  • .* 任意字符重复0次或者多次

语法
expr 字符串 “:” “.*”

xiao123@xiao123:~/Downloads/shscripts$ expr yc.png ":" ".*"
6
xiao123@xiao123:~/Downloads/shscripts$ expr yc.png ":" ".*"  #统计文件中字符个数
6
xiao123@xiao123:~/Downloads/shscripts$ expr yc.png ":" ".*j"  #最后的模式可以自定义
0
xiao123@xiao123:~/Downloads/shscripts$ expr yc.png ":" "p.*"  #最后的模式可以自定义
0
xiao123@xiao123:~/Downloads/shscripts$ expr yc.png ":" "y.*"  #最后的模式可以自定义
6
xiao123@xiao123:~/Downloads/shscripts$ expr yc.png ":" ".*p"  #最后的模式可以自定义
4
xiao123@xiao123:~/Downloads/shscripts$

脚本开发
需求：执行脚本，传入一个文件名，然后判断该文件，是否是jpg图片文件

xiao123@xiao123:~/Downloads/shscripts$ ./expr_test.sh chaochao_1.jpg
这的确是chaochao_1.jpg结尾的文件
xiao123@xiao123:~/Downloads/shscripts$ cat ./expr_test.sh
#! /bin/bashif expr "$1" ":" ".*\.jpg" >> /dev/nullthenecho "这的确是$1结尾的文件"
elseecho "这不是jpg结尾的文件"
fi
xiao123@xiao123:~/Downloads/shscripts$

找出长度不大于为5的单词

xiao123@xiao123:~/Downloads/shscripts$ ./expr_test1.sh
I
am
Yu
I
you
to
xiao123@xiao123:~/Downloads/shscripts$ cat ./expr_test1.sh
#! /bin/bashfor str1 in I am Yu chao, I teach you to learn linux.doif [ `expr length ${str1}` -lt 5 ]thenecho ${str1}fidone
xiao123@xiao123:~/Downloads/shscripts$

bc 命令

bc计算器
awk支持数值计算
中括号运算

bc当作计算器来用的，命令行的计算器。
例子1

xiao123@xiao123:~/Downloads/shscripts$ bc
bc 1.07.1
Copyright 1991-1994, 1997, 1998, 2000, 2004, 2006, 2008, 2012-2017 Free Software Foundation, Inc.
This is free software with ABSOLUTELY NO WARRANTY.
For details type `warranty'.
2+2
4
4*4
16
1-1
0
1-2
-1
2.24/2
1
2.2/2.0
1
2.22-1.1
1.12
^C
(interrupt) use quit to exit.
exit
0
^C
(interrupt) use quit to exit.
quit
xiao123@xiao123:~/Downloads/shscripts$

例子2

xiao123@xiao123:~/Downloads/shscripts$ num=5
xiao123@xiao123:~/Downloads/shscripts$ echo ${num}*5 | bc
25
xiao123@xiao123:~/Downloads/shscripts$

案例

计算出1-1000的总和
数学公式
1+2+3+4+…+100

xiao123@xiao123:~/Downloads/shscripts$ echo {1..100}
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100
xiao123@xiao123:~/Downloads/shscripts$ #tr 替换
xiao123@xiao123:~/Downloads/shscripts$ echo {1..100} | tr " " "+" #方案1
1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20+21+22+23+24+25+26+27+28+29+30+31+32+33+34+35+36+37+38+39+40+41+42+43+44+45+46+47+48+49+50+51+52+53+54+55+56+57+58+59+60+61+62+63+64+65+66+67+68+69+70+71+72+73+74+75+76+77+78+79+80+81+82+83+84+85+86+87+88+89+90+91+92+93+94+95+96+97+98+99+100
xiao123@xiao123:~/Downloads/shscripts$ seq -s "+" 100  #方案2
1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20+21+22+23+24+25+26+27+28+29+30+31+32+33+34+35+36+37+38+39+40+41+42+43+44+45+46+47+48+49+50+51+52+53+54+55+56+57+58+59+60+61+62+63+64+65+66+67+68+69+70+71+72+73+74+75+76+77+78+79+80+81+82+83+84+85+86+87+88+89+90+91+92+93+94+95+96+97+98+99+100
xiao123@xiao123:~/Downloads/shscripts$
xiao123@xiao123:~/Downloads/shscripts$ echo {1..100} | tr " " "+" | bc
5050
xiao123@xiao123:~/Downloads/shscripts$
xiao123@xiao123:~/Downloads/shscripts$ echo $((`echo {1..100} | tr " " "+"`))
5050
xiao123@xiao123:~/Downloads/shscripts$
xiao123@xiao123:~/Downloads/shscripts$ seq -s " + " 100 | xargs expr
5050
xiao123@xiao123:~/Downloads/shscripts$

awk计算

awk支持小数计算。

xiao123@xiao123:~/Downloads/shscripts$ seq -s " + " 100 | xargs expr
5050
xiao123@xiao123:~/Downloads/shscripts$ echo "2.2" "3.0" | awk '{print $1*$2}'
6.6
xiao123@xiao123:~/Downloads/shscripts$ echo "2.2" "3.0" | awk '{print ($1*$2)}'
6.6
xiao123@xiao123:~/Downloads/shscripts$ echo "2.2" "3.0" | awk '{print ($1*$2)+4}'
10.6
xiao123@xiao123:~/Downloads/shscripts$ echo "2.2" "3.0" | awk '{print $1*$2+4}'
10.6
xiao123@xiao123:~/Downloads/shscripts$

中括号计算

$[表达式]

xiao123@xiao123:~/Downloads/shscripts$ num=5
xiao123@xiao123:~/Downloads/shscripts$ res=$[num+4]
xiao123@xiao123:~/Downloads/shscripts$ echo ${res}
9
xiao123@xiao123:~/Downloads/shscripts$ res=$[num-4]
xiao123@xiao123:~/Downloads/shscripts$ echo ${res}
1
xiao123@xiao123:~/Downloads/shscripts$ res=$[num*4]
xiao123@xiao123:~/Downloads/shscripts$ echo ${res}
20
xiao123@xiao123:~/Downloads/shscripts$ res=$[num/4]
xiao123@xiao123:~/Downloads/shscripts$ echo ${res}
1
xiao123@xiao123:~/Downloads/shscripts$
http://www.tj-hxxt.cn/news/44696.html

相关文章：

  • 关于文化馆网站建设的材料百度站长社区
  • 如何提高网站点击率全网模板建站系统
  • 可以做哪些网站百度账号人工客服电话
  • 微店深圳关键词seo
  • 1网站免费建站网站优化seo培
  • 计算机网络工程师中级职称seo网站排名优化公司哪家好
  • 重庆建站多少钱一年女教师遭网课入侵直播录屏曝光i
  • 网站开发相关知识磁力吧最佳搜索引擎
  • 直播网站开发技术夫唯seo
  • 下拉框代码自做生成网站百度seo不正当竞争秒收
  • 做外贸有哪些网站比较好百度知道推广软件
  • 二手车网站模版免费推广的网站有哪些
  • 免费的素材网站有哪些友情链接联盟
  • wordpress给公司建站深圳外贸网站建设
  • 淘宝客如何做返积分制网站微信推广怎么做
  • 手机响应式网站开发什么是软文营销
  • 软装设计师培训中心免费seo优化
  • 手机网站建站流程发广告推广平台
  • 电子商务网站设计怎么做今日国内新闻10则
  • app应用网站源码友情链接也称为
  • 网页美工课程什么是seo搜索优化
  • 全国电子网站建设seo公司排行
  • 公司建立自己的网站吗广州关键词搜索排名
  • 分析苏宁易购的网站建设电商网站前端页面内容编写
  • wordpress 标题分隔符专业培训seo的机构
  • 马云不会代码怎么做的网站石家庄seo网络优化的公司
  • 做网站推广用优化还是竞价镇江网站建设企业
  • 建网站的公司广州排名seo排名赚app靠谱吗
  • 哈尔滨网站设计公司好短视频推广引流方案
  • 网站建设服务器费用淘宝指数在哪里查询