Linux运维必备之shell脚本编写规范与执行方式详解

#!/bin/bash
# Author: 作者名
# Mail: 联系方式
# Date: 日期
# Describe: 脚本描述
# Warning: 警告信息
# Version: 版本号
# Modify: 修改记录

autocmd BufNewFile *.py,*.cc,*.sh,*.java exec ":call SetTitle()"
func SetTitle()
    if expand("%:e") == 'sh'
        call setline(1,"#!/bin/bash")
        call setline(2,"##############################################################")
        call setline(3, "# File Name: ".expand("%"))
        call setline(4, "# Version: V1.0")
        call setline(5, "# Author: yourname")
        call setline(6, "# Email: your@email.com")
        call setline(7, "# Created Time : ".strftime("%F %T"))
        call setline(8, "# Description:")
        call setline(9,"##############################################################")
        call setline(10, "")
    endif
endfunc

<<EOF
这是多行注释
不会被执行
EOF

#!/bin/bash
# useradd.sh
useradd $1
echo $2 | passwd --stdin $1

#!/bin/bash
read -p "请输入用户名: " username
read -s -p "请输入密码: " password
useradd $username
echo $password | passwd --stdin $username
echo "$username 创建成功，密码已设置"

#!/bin/bash
read -p "请输入密码: " pass
echo $pass | grep 12345 -q
if [ $? -eq 0 ]; then
    echo "密码不能包含12345"
    exit 1
fi
echo "密码合法"

# 创建用户并设置密码
useradd luojiyu && echo 1 | passwd --stdin luojiyu

# 如果用户存在则修改密码，否则创建
useradd devops || echo 1 | passwd --stdin devops

# 判断IP是否通，根据结果写入不同文件
ping -c4 10.10.10.1 &>/dev/null && echo 10.10.10.1 > /opt/ip-ok.txt || echo 10.10.10.1 > /opt/ip-error.txt

command1; command2; command3

(cd /tmp; pwd)   

{ cd /tmp; pwd; }   

test root = 123 ; echo $?     # 返回1
[ 1 -eq 1 ]; echo $?          # 返回0
[[ "abc" == a* ]]; echo $?    # 支持通配符，返回0

# 如果/tmp/passwd不存在则拷贝
[ -e /tmp/passwd ] || cp /etc/passwd /tmp/passwd

# 如果useradd有执行权限则拷贝并修改所有者
[ -x /usr/sbin/useradd ] && cp /usr/sbin/useradd /tmp && chown devops /tmp/useradd

# 如果文件没有读权限则添加
[ -r /tmp/passwd ] || chmod a+r /tmp/passwd

disk_num=$(df | grep -w / | awk '{print $5}' | tr -d %)
if [ $disk_num -ge 10 ]; then
    rm -rf /tmp/*
    echo "tmp目录已清空"
else
    echo "disk free，使用率: ${disk_num}%"
fi

# 判断输入是否为root
read -p "输入用户名: " name
[ "$name" = "root" ] && echo "UID: $(id -u root)" || exit

# 检查参数是否为空
[ -z $1 ] && echo "请传入参数" || echo "参数是: $1"

# 用户名是zhangsan 且 UID>=1000
[ "$username" = "zhangsan" -a $useruid -ge 1000 ] && echo ok || echo error

# 使用[[ ]]
[[ "$username" = "zhangsan" && $useruid -ge 1000 ]] && echo ok

if 条件表达式; then
    执行语句
fi


# 第二种写法
if 条件表达式
then
    执行语句
fi

#!/bin/bash
read -p "输入用户名: " name
if id $name &>/dev/null; then
    echo "$name 已存在，不能创建"
    exit
fi
useradd $name

if 条件表达式; then
    语句1
else
    语句2
fi

#!/bin/bash
read -p "输入用户名: " name
if id $name &>/dev/null; then
    read -p "重置密码: " pass
    echo $pass | passwd --stdin $name
else
    useradd $name
    echo 1 | passwd --stdin $name
fi

#!/bin/bash
read -p "要备份的文件路径: " src
read -p "备份目录路径: " dst
if [ -d "$dst" ]; then
    chmod 777 $dst
else
    mkdir $dst
fi
cp -a $src $dst/$(basename $src)-$(date +%F).bak

if 条件1; then
    语句1
elif 条件2; then
    语句2
else
    语句3
fi

read -p "请输入成绩(0-100): " score
if [ $score -ge 85 ]; then
    echo "优秀 - A"
elif [ $score -ge 70 ]; then
    echo "良好 - B"
elif [ $score -ge 60 ]; then
    echo "合格 - C"
else
    echo "不合格 - D"
fi

case 变量 in
    模式1)
        命令
        ;;
    模式2)
        命令
        ;;
    *)
        默认命令
        ;;
esac

read -p "请输入成绩(0-100): " score
case $score in
    8[5-9]|9[0-9]|100)
        echo "优秀 - A"
        ;;
    7[0-9]|8[0-4])
        echo "良好 - B"
        ;;
    6[0-9])
        echo "合格 - C"
        ;;
    *)
        echo "不合格 - D"
        ;;
esac

for 变量名 in 列表; do
    命令
done

# 1. 直接列出
for i in 1 2 3 4 5; do echo $i; done

# 2. 大括号（支持数字和字母）
for i in {1..5}; do echo $i; done
for c in {a..z}; do echo $c; done

# 3. seq命令
for i in $(seq 1 5); do echo $i; done

# 4. 命令执行结果
for file in $(ls *.sh); do echo $file; done

for ((i=1; i<=10; i++)); do
    echo $i
done

for user in $(cat userlist.txt); do
    useradd $user
    echo 123456 | passwd --stdin $user
done

for i in {1..254}; do
    ip="192.168.1.$i"
    ping -c2 -W1 $ip &>/dev/null
    if [ $? -eq 0 ]; then
        echo "$ip is up"
    else
        echo "$ip is down"
    fi
done

while 条件表达式; do
    命令
done

# 方式1：exec重定向
exec < file.txt
while read line; do
    echo $line
done

# 方式2：管道
cat file.txt | while read line; do
    echo $line
done

# 方式3：重定向结尾（推荐）
while read line; do
    echo $line
done < file.txt

# iplist内容：
# 192.168.1.101 22
# 192.168.1.102 80
while read line; do
    IP=$(echo $line | awk '{print $1}')
    PORT=$(echo $line | awk '{print $2}')
    echo "IP: $IP, PORT: $PORT"
done < iplist

until 条件表达式; do
    命令
done

until [ -f /tmp/ready ]; do
    echo "等待文件..."
    sleep 2
done
echo "文件已出现"

# break: 当i=4时跳出
for i in {1..10}; do
    if [ $i -eq 4 ]; then
        break
    fi
    echo $i
done
# 输出: 1 2 3

# continue: 当i=4时跳过
for i in {1..10}; do
    if [ $i -eq 4 ]; then
        continue
    fi
    echo $i
done
# 输出: 1 2 3 5 6 7 8 9 10

#!/bin/bash
# 检查是否root用户
if [ $EUID -ne 0 ]; then
    echo "请使用root用户执行"
    exit 1
fi

# 安装依赖
yum install -y gcc make pcre-devel zlib-devel

# 下载并编译安装Nginx
cd /usr/local/src
wget http://nginx.org/download/nginx-1.24.0.tar.gz
tar xf nginx-1.24.0.tar.gz
cd nginx-1.24.0
./configure --prefix=/usr/local/nginx
make && make install

# 启动
/usr/local/nginx/sbin/nginx
echo "Nginx部署完成"

#!/bin/bash
read -p "请输入用户名: " username
if id $username &>/dev/null; then
    echo "用户已存在"
    exit 1
fi
read -s -p "请输入密码: " password
read -s -p "确认密码: " password2
echo
if [ "$password" != "$password2" ]; then
    echo "两次密码不一致"
    exit 1
fi
useradd $username
echo $password | passwd --stdin $username &>/dev/null
echo "用户 $username 创建成功"

#!/bin/bash
# 监控CPU、内存、磁盘使用率
cpu=$(top -bn1 | grep "Cpu(s)" | awk '{print $2}' | cut -d'%' -f1)
mem=$(free | grep Mem | awk '{printf "%.2f", $3/$2 * 100}')
disk=$(df -h / | awk 'NR==2 {print $5}' | tr -d '%')

echo "CPU使用率: $cpu%"
echo "内存使用率: $mem%"
echo "根分区使用率: $disk%"

if [ $disk -gt 80 ]; then
    echo "警告：磁盘空间不足"
fi