shell脚本批量创建用户

#!/bin/bash
DATE=$(date +%F_%T)
USER_FILE=user.txt
echo_color() {
    if [ $ == "green" ];then
        echo -e "\033[32;40m$2\033[0m"
    elif [ $ == "red" ];then
        echo -e "\033[31;40m$2\033[0m"
    fi
}
#如果用户文件存在并大小大于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\tPaassword" >> $USER_FILE
echo "--------------------" >> $USER_FILE
for USER in user{..};do
    if ! id $USER &>/dev/null; then
        PASS=$(echo $RANDOM | md5sum | cut -c -)
        useradd $USER
        echo $PASS |passwd --stdin $USER &>/dev/null
        echo -e "$USER\t$PASS" >> $USER_FILE
        echo "$USER User create successful."
    else
        echo_color red "$USER User already exists!"
    fi
done

其中用到的知识点：

　　echo $RANDOM 随机生成一串数字

　　md5sum将某串数字或字符转成长串字符

　　cut -c 1-8 取1到8位字符