Shell Scripting Exercises

#!/bin/bash
echo "Current datetime is:" ' Date '
echo "Hello world!"

#使用变量: You can use single or double quotation marks
Your_name= "Wang"
Echo $your _name
Echo ${your_name}
Str= ' Shellstudy '
Echo ${str}
#只读变量: Cannot change its value
Myurl= "Www.wnn1.com"
ReadOnly Myurl
echo "My URL is ${myurl}"
Myurl= "Www.wnn.com"
#删除变量: Read-only variables cannot be deleted
Unset Myurl
echo "My URL is ${myurl}"
#获取字符串长度
echo "str string is shellstudy and the string length is:" ${#str}
#提取子字符串: The following instance intercepts 4 characters starting from the 2nd character of the string
String= "Wangniannian"
echo "Intercept string" ${string:1:4}
#查找子字符串
echo ' expr index ' $string ' W '

#for循环
For skill in Ada coffe Action java;do
echo "I am good at ${skill}script"
Done

#数组
Array_name= (Wang Love Zhu)
#读取数组
echo "The second element of the array is:" ${array_name[1]}
#使用 @ can get all the elements in the array
echo "All elements of the array are:" ${array_name[@]}
#取得数组元素的个数
length=${#array_name [@]}
echo "Array with the number of elements:" ${length}
#取得数组单个元素的长度
lengthn=${#array_name [2]}
The length of the third element of the echo "array is:" ${lengthn}

#Shell Pass Parameters
echo "Executed file name: $"
echo "First parameter: $ $"
echo "The second parameter is: $"

#Shell operator: Native bash does not support simple math operations, but can be implemented with other commands, such as awk and expr,expr, which are most commonly used.
#expr is an expression calculation tool that uses it to perform the evaluation of an expression.

#算数运算符
Val= ' Expr 2 + 2 '
echo "2+2= $val"

a=10
echo "A's value is ${a}"
B=20
echo "B's value is ${b}"

Val_jia= ' expr $a + $b '
echo "a+b= $val _jia"

val_jian= ' expr $a + $b '
echo "a-b= $val _jian"

# * need to have \ need to escape in front
val_cheng= ' expr $a \* $b '
echo "a*b= $val _cheng"

val_chu= ' expr $b/$a '
echo "B/a= $val _chu"

val_yu= ' expr $b% $a '
echo "B%a= $val _yu"

if [$a = = $b]
Then echo "a equals B"
Fi
if [$a! = $b]
Then echo "A is not equal to B"
Fi

#关系运算符
#-eq detects whether two numbers are equal and returns true for equality
If [$a-eq $b]
Then echo "$a-eq $b: a equals B"
else echo "$a-eq $b: A is not equal to B"
Fi
#ne detects whether two numbers are equal, not equal returns True
If [$a-ne $b]
Then echo "$a-ne $b: A is not equal to B"
else echo "$a-ne $b: a equals B"
Fi
#gt detects if the number on the left is greater than the right, and if yes, returns true
If [$a-gt $b]
Then echo "$a-gt $b: a greater than B"
else echo "$a-gt $b: A is not much more than B"
Fi
#lt detects if the number on the left is less than the right, and if yes, returns true
If [$a-lt $b]
Then echo "$a-lt $b: a less than B"
else echo "$a-lt $b: A is not less than B"
Fi
#ge detects if the number on the left is greater than or equal to the right, and if yes, returns true
If [$a-ge $b]
Then echo "$a-ge $b: A is greater than or equal to B"
else echo "$a-ge $b: a less than B"
Fi
#le detects if the left number is less than or equal to the right, and if yes, returns true
If [$a-le $b]
Then echo "$a-le $b: A is less than or equal to B"
else echo "$a-le $b: a greater than B"
Fi

#布尔运算符

#逻辑运算符

#字符串运算符

#文件测试运算符

#Shell Input and output redirection
#/dev/null file: If you want to execute a command but do not want the output to be displayed on the screen, you can redirect the output to/dev/null:
#/dev/null is a special file, and the content written to it is discarded, and if you try to read from the file, nothing is read. However, the/dev/null file is very useful and redirects the output of the command to it, which results in a "no output" effect.

#输出重定向
Who > Users
#追加用 >>
echo "Rookie tutorial: Www.runoob.com" >>users

#输入重定向
Wc-l Users

#Shell函数
Demofun () {
echo "This is my first Shell function!"
}
echo "---function starts execution---"
Demofun
echo "---function completed---"

#Shell Process Control

If [$ (ps-ef | grep-c "SSH")-GT 1]
Then echo "true"
else echo "false"
Fi

#grep命令
#查找包含wang文本的所有行并打印在屏幕上
grep "Wang"/users/wangniannian/test.sh
#不区分大小写的查找wang文本的所有行并打印在屏幕上
Grep-i "Wang"/users/wangniannian/test.sh
#查找包含wang文本的所有行并将匹配行的总数打印在屏幕上
Grep-c "Wang"/users/wangniannian/test.sh
#查找包含wang文本的所有行并打印在屏幕上同时显示行号
Grep-n "Wang"/users/wangniannian/test.sh
#查找不包含wang文本的所有行并打印仔屏幕上
Grep-v "Wang"/users/wangniannian/test.sh

#awk
#用法一: awk ' {[Pattern] action} ' {filenames} # line match statement awk ' can only use single quotes
#每行按空格或TAB分割, 1, 4 items in the output text
awk ' {print $1,$4} ' Log.txt
#格式化输出
awk ' {printf '%-8s%-10s\n ", $1,$4} ' Log.txt

#用法二: Awk-f #-f equivalent to built-in variable FS, specifying split characters, for example, splitting
Awk-f, ' {print $1,$2} ' Log.txt
#或者使用内建变量
awk ' BEGIN {fs= ', '} {print $1,$2} ' Log.txt
#使用多个分隔符, use a space partition first, then use the split result again, split
Awk-f ' [,] ' {print $1,$2,$5} ' Log.txt

#用法三: Awk-v Setting variables
Awk-va = 1 ' {print $1,$1+a} ' Log.txt

Awk-va = 1-vb = S ' {print $1,$1+a,$1b} ' Log.txt

#用法四: awk-f {awk script} {file name}
Awk-f Cal.awk Log.txt

#运算符
#过滤第一列大于2的行
awk ' $1>2 ' Log.txt
#过滤第一列等于2的行
awk ' $1==2 {print $1,$3} ' Log.txt
#过滤第一列大于2并且第二列等于 ' is ' line
awk ' $1>2 && $2== ' is ' {print $1,$2,$3} ' Log.txt

#xargs

#read

#find
Find ~-name adb

Find. -name ADB

Shell Scripting Exercises