bash 检查用户是否存在
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Check Whether a User Exists
提问by slayedbylucifer
I want to create a script to check whether a user exists. I am using the logic below:
我想创建一个脚本来检查用户是否存在。我正在使用以下逻辑：
# getent passwd test > /dev/null 2&>1
# echo $?
0
# getent passwd test1 > /dev/null 2&>1
# echo $?
2
So if the user exists, then we have success, else the user does not exist. I have put above command in the bash script as below:
所以如果用户存在，那么我们就成功了，否则用户不存在。我已将上述命令放在 bash 脚本中，如下所示：
#!/bin/bash
getent passwd > /dev/null 2&>1
if [ $? -eq 0 ]; then
echo "yes the user exists"
else
echo "No, the user does not exist"
fi
Now, my script always says that the user exists no matter what:
现在，我的脚本总是说无论如何用户都存在：
# sh passwd.sh test
yes the user exists
# sh passwd.sh test1
yes the user exists
# sh passwd.sh test2
yes the user exists
Why does the above condition always evaluate to be TRUE and say that the user exists?
为什么上述条件总是评估为 TRUE 并说用户存在？
Where am I going wrong?
我哪里错了？
UPDATE:
更新：
After reading all the responses, I found the problem in my script. The problem was the way I was redirecting getentoutput. So I removed all the redirection stuff and made the getentline look like this:
阅读所有回复后，我在我的脚本中发现了问题。问题是我重定向getent输出的方式。所以我删除了所有重定向的东西，让这getent行看起来像这样：
getent passwd $user > /dev/null
Now my script is working fine.
现在我的脚本工作正常。
回答by Kent
you can also check user by idcommand.
您也可以通过id命令检查用户。
id -u namegives you the id of that user.
if the user doesn't exist, you got command return value ($?)1
id -u name给你那个用户的id。如果用户不存在，您将获得命令返回值 ( $?)1
回答by poitroae
Why don't you simply use
你为什么不简单地使用
grep -c '^username:' /etc/passwd
It will return 1 (since a user has max. 1 entry) if the user exists and 0 if it doesn't.
如果用户存在，它将返回 1（因为用户最多有 1 个条目），如果用户不存在则返回 0。
回答by chepner
There's no need to check the exit code explicitly. Try
无需明确检查退出代码。尝试
if getent passwd > /dev/null 2>&1; then
echo "yes the user exists"
else
echo "No, the user does not exist"
fi
If that doesn't work, there is something wrong with your getent, or you have more users defined than you think.
如果这不起作用，则getent您的 有问题，或者您定义的用户比您想象的要多。
回答by Daniel Sokolowski
This is what I ended up doing in a Freeswitchbash startup script:
这就是我最终在Freeswitchbash 启动脚本中所做的：
# Check if user exists
if ! id -u $FS_USER > /dev/null 2>&1; then
echo "The user does not exist; execute below commands to crate and try again:"
echo " root@sh1:~# adduser --home /usr/local/freeswitch/ --shell /bin/false --no-create-home --ingroup daemon --disabled-password --disabled-login $FS_USER"
echo " ..."
echo " root@sh1:~# chown freeswitch:daemon /usr/local/freeswitch/ -R"
exit 1
fi
回答by Valdas Rap?evi?ius
I suggest to use id command as it tests validuser existence wrt passwd file entry which is not necessary means the same:
我建议使用 id 命令，因为它测试有效的用户存在 wrt passwd 文件条目，这不是必需的，意思相同：
if [ `id -u $USER_TO_CHECK 2>/dev/null || echo -1` -ge 0 ]; then
echo FOUND
fi
Note: 0 is root uid.
注意：0 是根 uid。
回答by Takeda
I was using it in that way:
我是这样使用它的：
if [ $(getent passwd $user) ] ; then
echo user $user exists
else
echo user $user doesn\'t exists
fi
回答by Fleshgrinder
By far the simplest solution:
到目前为止最简单的解决方案：
if id -u user >/dev/null 2>&1; then
echo user exists
else
echo user missing
fi
The >/dev/null 2>&1can be shortened to &>/dev/nullin Bash.
该>/dev/null 2>&1可缩短到&>/dev/nullBash中。
回答by Bakul Gupta
Script to Check whether Linux user exists or not
Script To check whether the user exists or not
Script 检查用户是否存在
#! /bin/bash
USER_NAME=bakul
cat /etc/passwd | grep ${USER_NAME} >/dev/null 2>&1
if [ $? -eq 0 ] ; then
echo "User Exists"
else
echo "User Not Found"
fi
回答by Hymanotonye
Late answer but fingeralso shows more information on user
迟到的答案，但finger也显示了有关用户的更多信息
sudo apt-get finger
finger "$username"
回答by Yu Chai
user infomation is stored in /etc/passwd, so you can use "grep 'usename' /etc/passwd" to check if the username exist. meanwhile you can use "id" shell command, it will print the user id and group id, if the user does not exist, it will print "no such user" message.
用户信息存储在 /etc/passwd 中，因此您可以使用“grep 'usename' /etc/passwd”来检查用户名是否存在。同时你可以使用“id”shell命令，它会打印用户ID和组ID，如果用户不存在，它会打印“没有这样的用户”消息。
