Check if user exists

Question

How can I in bash check if a user exists, but in such a way that script work in multiple systems ?

A limited example:

grep <username> /etc/passwd

Does not work on systems that use NIS or LDAP to manage users.

Answer 1

The command getent should work in this case.

getent passwd <usuario>

The command getent displays database entries supported by Service Switch, which are configured in the file /etc/nsswitch.conf.

Another alternative that may work in this case is to check whether the ID user is valid through the command id, using with the option -u:

if id -u "usuario" > /dev/null 2>&1; then
        echo "Utilizador existe"
else
        echo "O utilizador especificado não existe"
fi