Bash脚本检查是否存在多个组

Question

我需要使用以下命令将用户添加到多个补充组中

usermod -aG group1,group2 username

需要帮助以进行错误检查，以便脚本可以搜索/ etc / group文件中是否存在多个组。 这就是我所拥有的。

read -p "Enter groups" groups
if (Check if those groups exists)
then
  usermod -aG "$groups $username
else
  echo "Group(s) does not exists"
fi

请帮忙谢谢！ 对不起，我是一个新手，如果可能的话，请告诉我一些阅读链接。

好吧，我提出了一些切实可行的方法。 如果它可以被某人“清理”，将不胜感激。 XD

    read -p "Enter user" user
    read -p "Enter groups" groups
    storegroups=$(echo $groups | awk -F, '{print $1" "$2" "$3}')
    if [ "$(getent group $storegroups | wc -l)" == $(echo $storegroups | wc -w)" ]
    then 
        usermod -ag $groups $user
    else
        echo "1 or more groups does not exists"
    fi

Answer 1

#!/bin/bash

read -p "Enter username: " username
read -p "Enter groups: " groups

for g in ${groups//,/ }; do
  grep -q "^$g:" /etc/group
  ret=$?                         # save returncode of grep
  if [[ $ret -eq 0 ]]; then
    usermod -aG "$g" "$username"
  else
    echo "Group $g does not exists"
  fi
done

Answer 2

read -p "Enter user: " user
read -p "Enter groups: " groups

# Replace , with space
groupswithSpace=$(echo $groups | tr ',' ' ')

#getent returns 0 only if all groups are valid
getent group $groupswithSpace > /dev/null

if [ $? -eq 0 ]
then
    usermod -ag $groups $user
else
    echo "1 or more groups does not exists"
fi