Check Whether a User Exists

Question

I want to create a script to check whether a user exists. I am using the logic below:

# getent passwd test > /dev/null 2&>1
# echo $?
0
# getent pa         


        

Answer 1

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.

Answer 2

Login to the server. grep "username" /etc/passwd This will display the user details if present.

Answer 3

There's no need to check the exit code explicitly. Try

if getent passwd $1 > /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.

Answer 4

Why don't you simply use

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.

Answer 5

I suggest to use id command as it tests valid user existence wrt passwd file entry which is not necessary means the same:

if [ `id -u $USER_TO_CHECK 2>/dev/null || echo -1` -ge 0 ]; then 
echo FOUND
fi

Note: 0 is root uid.

Answer 6

Depending on your shell implementation (e.g. Busybox vs. grown-up) the [ operator might start a process, changing $?.

Try

getent passwd $1 > /dev/null 2&>1
RES=$?

if [ $RES -eq 0 ]; then
    echo "yes the user exists"
else
    echo "No, the user does not exist"
fi