Shell脚本常用示例

While 循环

#!/bin/bash
i=0

while [ $i -le 2 ]
do
echo Number: $i
((i++))
done

因此，while 循环采用以下形式。

while [ condition ]
do
commands 1
commands n
done

For 循环

#!/bin/bash

for (( counter=1; counter<=10; counter++ ))
do
echo -n "$counter "
done

printf "\n"

接收用户输入

#!/bin/bash

echo -n "Enter Something:"
read something

echo "You Entered: $something"

IF 语句

if CONDITION 
then
STATEMENTS
fi

#!/bin/bash
echo -n "Enter a number:"
read num

if [[$num -gt 10]]
then
    echo "Number is greater than 10."
fi

#!/bin/bash

echo -n "Enter a number: "
read num

if [[ $num -gt 10 ]]
then
    echo "Number is greater than 10."
elif [[ $num -eq 10 ]]
then
    echo "Number is equal to 10."
else
    echo "Number is less than 10."
fi

#!/bin/bash

echo -n "Enter Number:"
read n
if [ $n -lt 10 ];
then
    echo "It is a one digit number"
else
    echo "It is a two digit number"
fi

使用 AND 运算符

#!/bin/bash

echo -n "Enter Number:"
read num

if [[ ( $num -lt 10 ) && ( $num%2 -eq 0 ) ]]; then
    echo "Even Number"
else
    echo "Odd Number"
fi

使用 OR 运算符

#!/bin/bash

echo -n "Enter any number:"
read n

if [[ ( $n -eq 15 || $n -eq 45 ) ]]
then
    echo "You won"
else
    echo "You lost!"
fi

case 条件

#!/bin/bash

echo -n "Enter a number: "
read num

case $num in
100)
    echo "Hundred!!" ;;
200)
    echo "Double Hundred!!" ;;
*)
    echo "Neither 100 nor 200" ;;
esac

命令行参数

#!/bin/bash
echo "Total arguments : $#"
echo "First Argument = $1"
echo "Second Argument = $2"


# test.sh
./test.sh Hey Howdy

使用名称获取参数

#!/bin/bash

for arg in "$@"
do
    index=$(echo $arg | cut -f1 -d=)
    val=$(echo $arg | cut -f2 -d=)

    case $index in
        X) x=$val;;
        Y) y=$val;;
    *)
    esac
done

((result=x+y))
echo "X+Y=$result"

调用

./test.sh X=44 Y=100

连接字符串

#!/bin/bash

string1="Ubuntu"
string2="Pit"
string=$string1$string2

echo "$string is a great resource for Linux beginners."

字符串截取

#!/bin/bash
Str="Learn Bash Commands from UbuntuPit"
subStr=${Str:0:20}
echo $subStr

使用 cut 做截取

#!/bin/bash
Str="Learn Bash Commands from UbuntuPit"
#subStr=${Str:0:20}

subStr=$(echo $Str| cut -d ' ' -f 1-3)
echo $subStr

添加两个值

#!/bin/bash
echo -n "Enter first number:"
read x

echo -n "Enter second number:"
read y

(( sum=x+y ))
echo "The result of addition=$sum"

添加多个值

#!/bin/bash
sum=0
for (( counter=1; counter<5; counter++ ))
do
    echo -n "Enter Your Number:"
    read n
    (( sum+=n ))
    #echo -n "$counter "
done

printf "\n"
echo "Result is: $sum"

Bash 中的函数

#!/bin/bash
function Add()
{
    echo -n "Enter a Number: "
    read x
    echo -n "Enter another Number: "
    read y
    echo "Adiition is: $(( x+y ))"
}

Add

具有返回值的函数

#!/bin/bash

function Greet() {
    str="Hello $name, what brings you to UbuntuPit.com?"
    echo $str
}

echo "-> what's your name?"
read name

val=$(Greet)
echo -e "-> $val"

从 Bash 脚本创建目录

#!/bin/bash
echo -n "Enter directory name ->"
read newdir
cmd="mkdir $newdir"
eval $cmd

确认存在后创建目录

#!/bin/bash
echo -n "Enter directory name ->"
read dir

if [ -d "$dir" ]
then
    echo "Directory exists"
else
    `mkdir $dir`
    # 或者 cmd="mkdir $dir" ; eval $cmd
    echo "Directory created"
fi

读取文件

#!/bin/bash
file='editors.txt'

while read line; do
    echo $line
done < $file

删除文件

#!/bin/bash
echo -n "Enter filename ->"
read name
rm -i $name

附加到文件

#!/bin/bash
echo "Before appending the file"
cat editors.txt
echo "6. NotePad++" >> editors.txt
echo "After appending the file"
cat editors.txt

测试文件存在

• -f 文件

• -d 文件夹

#!/bin/bash
filename=$1
if [ -f "$filename" ]; then
    echo "File exists"
else
    echo "File does not exist"
fi

从 Shell 脚本发送邮件

向收件人发送包含给定主题和消息的电子邮件

#!/bin/bash
recipient=”[e-mail]”
subject=”Greetings”
message=”Welcome to UbuntuPit”

`mail -s $subject $recipient <<< $message`

解析日期和时间

#!/bin/bash
year=`date +%Y`
month=`date +%m`
day=`date +%d`
hour=`date +%H`
minute=`date +%M`
second=`date +%S`
echo `date`
echo "Current Date is: $day-$month-$year"
echo "Current Time is: $hour:$minute:$second"


# Thu Apr 13 13:52:08 CST 2019
# Current Date is: 13-04-2019
# Current Time is: 13:52:08

sleep 命令

#!/bin/bash
echo "How long to wait?"
read time
sleep $time
echo "Waited for $time seconds!"

wait 命令

wait 命令用于暂停 Linux bash 脚本中的系统进程

#!/bin/bash
echo "Testing wait command"
sleep 5 &
pid=$!
kill $pid
wait $pid
echo $pid was terminated.

显示上次更新的文件

列出当前工作目录中最近更新或创建的文件

ls -lrt | grep ^- | awk 'END{print $NF}'

添加批处理扩展

对目录中的所有文件应用自定义扩展名

#!/bin/bash
dir=$1
for file in `ls $1/*`
do
    mv $file $file.pdf
done

打印文件或目录的数量

查找给定目录中存在的文件或文件夹的数量 如果指定的目录不可用或存在权限问题，程序将要求用户重试。

#!/bin/bash

if [ -d "$@" ]; then
    echo "Files found: $(find "$@" -type f | wc -l)"
    echo "Folders found: $(find "$@" -type d | wc -l)"
else
    echo "[ERROR] Please retry with another folder."
    exit 1
fi

清理日志文件

#!/bin/bash
LOG_DIR=/var/log
cd $LOG_DIR

cat /dev/null > messages
cat /dev/null > wtmp
echo "Logs cleaned up."

使用 Bash 备份脚本

备份过去 24 小时内修改的每个文件或目录

#!/bin/bash

BACKUPFILE=backup-$(date +%m-%d-%Y)
archive=${1:-$BACKUPFILE}

find . -mtime -1 -type f -print0 | xargs -0 tar rvf "$archive.tar"
echo "Directory $PWD backed up in archive file \"$archive.tar.gz\"."
exit 0

检查你是否是 root 用户

#!/bin/bash
ROOT_UID=0

if [ "$UID" -eq "$ROOT_UID" ]
then
    echo "You are root."
else
    echo "You are not root"
fi
exit 0

从文件中删除重复行

逐行遍历文件并删除所有重复的行。然后，它将新内容放入新文件，并保持原始文件的完整性。

#! /bin/sh

echo -n "Enter Filename-> "
read filename

if [ -f "$filename" ]; then
    sort $filename | uniq | tee sorted.txt
else
    echo "No $filename in $pwd...try again"
fi
exit 0

系统维护

#!/bin/bash

echo -e "\n$(date "+%d-%m-%Y --- %T") --- Starting work\n"

apt-get update
apt-get -y upgrade

apt-get -y autoremove
apt-get autoclean

echo -e "\n$(date "+%T") \t Script Terminated"