练习_用户存在_命令判断

#!/usr/bin/bash
read -p "please input a username：" user

id $user &>/dev/null  # id user 用户是否存在
if [ $? -ne 0 ];then
        echo "no such user: $user"
        exit 1
fi

read -p "Are you sure?[y/n]：" action
#if [ $action = "y" -o $action = "Y" -o $action = "YES" ];then  #-o 或者
#       userdel -r $user
#       echo "$user is deleted"
#fi

case "$action" in   
y|Y|yes|YES)  # 集合
        userdel -r $user
        echo "$user is deleted"
        ;;
*)
        echo "error"
        ;;
esac

　　

#!/usr/bin/bash

#判断命令是否存在

command1=/usr/bin/ls

if command -v $command1 &>/dev/null;then
        :                         #如果命令存在 则不执行任何操作
else
        echo "yum -y install xx"  #如果命令不存在 执行安装命令
fi