Shell logic: How to create user/group if no user/group with that UID/GID exists

The following bash / shell snippet is an example of how to create a user and group if no user/group with that UID/GID exists yet:

How to create a group if no group with that GID exists

getent group $GID || groupadd --gid $GID $USERNAME

How to create a user if no user with that UID exists

getent passwd $UID || useradd --uid $UID --gid $GID -m $USERNAME

How it works

• getent group $GID will return the group with the given GID if it exists, or nothing if it doesn’t. Example:

$ getent group 1000
myuser:x:1000:
$ echo $?
0

in case no such group exists:

$ getent group 12345
$ echo $?
2

After that, we will use || to execute the groupadd command only if getent returns a non-zero exit code (i.e., the group doesn’t exist).

• groupadd --gid $GID $USERNAME will create a group with the given GID and name.

How to include that into your script

Ensure to use braces if you are using this command in a && chain to avoid unexpected behavior.

Example:

# Create user/group only of no such user/group exists
(getent group $gid || groupadd --gid $gid $USERNAME) \
 && (getent passwd $uid || useradd --uid $uid --gid $gid -m $USERNAME) \
 && echo "Created user & group or used existing ones"