shell 案例

1、获取随机字符串或数字

获取随机8位字符串：

方法1：

# echo $RANDOM |md5sum |cut -c 1-8

471b94f2

方法2：

# openssl rand - 4

vg3BEg==

方法3：

# cat /proc/sys/kernel/random/uuid |cut -c 1-8

ed9e032c

获取随机8位数字：

方法1：

# echo $RANDOM |cksum |cut -c 1-8

23648321

方法2：

# openssl rand - 4 |cksum |cut -c 1-8

38571131

方法3：

# date +%N |cut -c 1-8

69024815

cksum：打印CRC效验和统计字节

2、定义一个颜色输出字符串函数

方法1：

function echo_color() {

if [ $1 == "green" ]; then

echo -e "\033[32;40m$2\033[0m"

elif [ $1 == "red" ]; then

echo -e "\033[31;40m$2\033[0m"

fi

}

方法2：

function echo_color() {

case $1 in

green)

echo -e "[32;40m$2[0m"

;;

red)

echo -e "[31;40m$2[0m"

;;

*)

echo "Example: echo_color red string"

esac

}

使用方法：echo_color green "test"

function关键字定义一个函数，可加或不加。

3、批量创建用户

#!/bin/bash

DATE=$(date +%F_%T)

USER_FILE=user.txt

echo_color(){

if [ $1 == "green" ]; then

echo -e "[32;40m$2[0m"

elif [ $1 == "red" ]; then

echo -e "[31;40m$2[0m"

fi

}

# 如果用户文件存在并且大小大于0就备份

if [ -s $USER_FILE ]; then

mv $USER_FILE ${USER_FILE}-${DATE}.bak

echo_color green "$USER_FILE exist, rename ${USER_FILE}-${DATE}.bak"

fi

echo -e "User Password" >> $USER_FILE

echo "----------------" >> $USER_FILE

for USER in user{1..10}; do

if ! id $USER &>/dev/null; then

PASS=$(echo $RANDOM |md5sum |cut -c 1-8)

useradd $USER

echo $PASS |passwd --stdin $USER &>/dev/null

echo -e "$USER $PASS" >> $USER_FILE

echo "$USER User create successful."

else

echo_color red "$USER User already exists!"

fi

done