练习_用户存在_命令判断

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#!/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

　　

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#!/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