Linux check if group exist

How to check if a group exists and add if it doesn’t in Linux Shell Script

I am using the Ubuntu virtual machine but all of the results i have found on similar sites do not work.

Linux Solutions

Solution 1 — Linux

The grep statement in the solution of rups has some flaws:

E.g. grepping for a group admin may return true («group exists») when there is a group lpadmin .

Either fix the grep -query

if [ $(getent group admin) ]; then echo "group exists." else echo "group does not exist." fi 

Solution 2 — Linux

 read -p "enter group name: " group if grep -q $group /etc/group then echo "group exists" else echo "group does not exist" fi 

Solution 3 — Linux

Grepping /etc/group works, but only on a machine where /etc/nsswitch.conf has:

meaning that only /etc/group is consulted when determining available groups. Use either of these (by name or by gid):

getent group getent group 

for a more generic solution, checking the exit status: 0 means «exists», non-zero means «does not exist». For example, to check to see if group ‘postgres’ exists, and create it if it does not (assuming bash shell, running as a user able to create new groups) run:

/usr/bin/getent group postgres 2>&1 > /dev/null || /usr/sbin/groupadd postgres 

Solution 4 — Linux

I’ve found it more useful, to compose andiba’s solution into a proper function:

function grpexists < if [ $(getent group $1) ]; then echo "group $1 exists." else echo "group $1 does not exist." fi > 

This can for e.g be invoked into your environment by including this function in your /etc/bash.bashrc* , such that you can then check for the existence of a group, using the following spell:

Which should then return one of:

> group group_name does not exist.

Solution 5 — Linux

Single line:

Solution 6 — Linux

Here are 3 commands which should work:

group=sudo grep -qw ^$group /etc/group || groupadd $group usermod -aG $group $USER 

Or one, when you use -f / —force (exit successfully if the group already exists):

groupadd -f mygroup && usermod -aG mygroup $USER 

Solution 7 — Linux

$ groupadd --help Usage: groupadd [options] GROUP Options: -f, --force exit successfully if the group already exists, and cancel -g if the GID is already used 

Solution 8 — Linux

Geeks great solutions and guidance, thanks for sharing here are my 2 cents to make our lives simpler or lazier 🙂 I could use to complement an useradd script I have to add several users at once. I’m wondering how it would look like inside a for in loop for several groups: group1, group2, group3. group6 Then useradd to the system something like this?

for g in $( cat fewgroups.txt ); do groupadd $g echo «Group:» $g «Exist not added moving on» else echo «Group:» $g «added successfully!» # Then create the users for u in $( cat 100sofusers.txt ); do useradd -m -g group1 -G group2,wheel -d /home/$u -c «Just anothe SiFiGeek» -s /bin/bash $u echo «userID:» $u «added successfully!» echo $u:$randompw | chpasswd echo «Password for userID:» $u «changed successfully» done

Источник

How to check if a group exists and add if it doesn’t in linux shell script?

When writing a shell script, it’s often necessary to check if a group already exists in the Linux system and, if not, add the group. The purpose of this can be to set up user privileges and permissions, ensure that the group is available for a specific process or application, or to maintain the organization and structure of groups on the system. In this answer, two methods will be discussed to achieve this goal:

Method 1: Using the «getent» Command

To check if a group exists and add it if it doesn’t in Linux Shell Script, you can use the «getent» command. Here are the steps:

1. First, you need to check if the group exists. You can use the «getent» command to do this. The «getent» command searches the databases configured in /etc/nsswitch.conf file. You can use it to search for groups in the «group» database.

if getent group group_name> >/dev/null 2>&1; then echo "Group exists" else echo "Group does not exist" fi

1. If the group does not exist, you can create it using the «groupadd» command. The «groupadd» command adds a new group to the system.

if ! getent group group_name> >/dev/null 2>&1; then groupadd group_name> echo "Group created" fi

1. You can also add a user to the group using the «usermod» command. The «usermod» command modifies the system account files to reflect the changes that are specified on the command line.

usermod -a -G group_name> user_name>

Here is the complete code:

#!/bin/bash group_name="mygroup" user_name="myuser" if getent group $group_name >/dev/null 2>&1; then echo "Group exists" else groupadd $group_name echo "Group created" fi usermod -a -G $group_name $user_name echo "User added to group"

This script checks if the group «mygroup» exists. If it does not exist, it creates it. Then it adds the user «myuser» to the group.

Method 2: Using the «grep» Command

To check if a group exists and add it if it doesn’t using the grep command in a Linux Shell Script, you can follow these steps:

1. First, use the grep command to search for the group name in the /etc/group file. If the group exists, the command will return a match. If it doesn’t exist, the command will return nothing.

if grep -q "^mygroup:" /etc/group; then echo "Group exists" else echo "Group does not exist" fi

if grep -q "^mygroup:" /etc/group; then echo "Group exists" else groupadd mygroup echo "Group created" fi

usermod -a -G mygroup user1 usermod -a -G mygroup user2

This will add user1 and user2 to the mygroup group.

This will delete the mygroup group.

These are the basic steps to check if a group exists and add it if it doesn’t using the grep command in a Linux Shell Script. You can modify these commands according to your requirements.

Источник

How to check if a group exists and add if it doesn’t in Linux Shell Script

I am using the Ubuntu virtual machine but all of the results i have found on similar sites do not work.

8 Answers 8

The grep statement in the solution of rups has some flaws:

E.g. grepping for a group admin may return true («group exists») when there is a group lpadmin .

Either fix the grep -query

if [ $(getent group admin) ]; then echo "group exists." else echo "group does not exist." fi 

You can chain getent to create the group if it doesn’t exist thusly: getent group admin || groupadd [options] admin You can further chain that with && useradd -G admin someuser to make a one-liner that should create the group if needed and then add the user to it.

The use of getent seems like the most direct answer to the question. It seems to avoid text-parsing corner cases and just returns a 0 or 2 exit code which is what we should be after in a function anyway.

Grepping /etc/group works, but only on a machine where /etc/nsswitch.conf has:

meaning that only /etc/group is consulted when determining available groups. Use either of these (by name or by gid):

getent group getent group

for a more generic solution, checking the exit status: 0 means «exists», non-zero means «does not exist». For example, to check to see if group ‘postgres’ exists, and create it if it does not (assuming bash shell, running as a user able to create new groups) run:

/usr/bin/getent group postgres 2>&1 > /dev/null || /usr/sbin/groupadd postgres 

getent isn’t available on macOS (and possibly all BSD) so it’s not exactly more generic — but it might be ok if you fall back to grep: getent group postgres || grep -q postgres /etc/group

 read -p "enter group name: " group if grep -q $group /etc/group then echo "group exists" else echo "group does not exist" fi 

This is pretty much what i started with that didnt work.. i will attach screenshots of the code and what happens when it runs edit i cant attach pictures edit

I’ve found it more useful, to compose andiba’s solution into a proper function:

This can for e.g be invoked into your environment by including this function in your /etc/bash.bashrc* , such that you can then check for the existence of a group, using the following spell:

Which should then return one of:

group group_name does not exist.

Single line:

Here are 3 commands which should work:

group=sudo grep -qw ^$group /etc/group || groupadd $group usermod -aG $group $USER 

Or one, when you use -f / —force (exit successfully if the group already exists):

groupadd -f mygroup && usermod -aG mygroup $USER 

For completeness, if the group fails to be added, there should be some error handling. E.g., sudo groupadd -f » && echo «success» || echo «fail»

$ groupadd --help Usage: groupadd [options] GROUP Options: -f, --force exit successfully if the group already exists, and cancel -g if the GID is already used 

Geeks great solutions and guidance, thanks for sharing here are my 2 cents to make our lives simpler or lazier 🙂 I could use to complement an useradd script I have to add several users at once. I’m wondering how it would look like inside a for in loop for several groups: group1, group2, group3. group6 Then useradd to the system something like this?

for g in $( cat fewgroups.txt ); do groupadd $g echo «Group:» $g «Exist not added moving on» else echo «Group:» $g «added successfully!» # Then create the users for u in $( cat 100sofusers.txt ); do useradd -m -g group1 -G group2,wheel -d /home/$u -c «Just anothe SiFiGeek» -s /bin/bash $u echo «userID:» $u «added successfully!» echo $u:$randompw | chpasswd echo «Password for userID:» $u «changed successfully» done

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Источник

Linux: Check if a User or a Group Exists 2

You can find out if user exists by searching in the /etc/passwd file using the following command:

egrep -i "^useraccount:" /etc/passwd

The above command will print the matching record from /etc/passwd if the user exists or nothing if the user does not exist.
The ^ symbol is used to make sure there is no characters before the username and the : character is used as the delimiter in the file (which indicates the end of the username). By wrapping the username with these characters we are sure that if we matched a record, we matched the correct record with the full username.

A very simple way to use this code in a script is by utilizing the $? (question mark) variable. The question mark variable contains the exit status of the last command that executed. Specifically, egrep will return 0 if there was a match or else it will return a a positive number (usually 1).
Taking advantage of this behavior, after executing the above command, we check the $? variable to see the result with an if statement.

egrep -i "^useraccount:" /etc/passwd; if [ $? -eq 0 ]; then echo "User Exists" else echo "User does not exist -- Invalid Username" fi

You can also find out if a group exists by searching in the /etc/group file. Similar to the approach we showed before, we can check if a group exists using the following:

egrep -i "^groupname" /etc/group; if [ $? -eq 0 ]; then echo "Group Exists" else echo "Group does not exist -- Invalid Group name" fi

Источник

How to check if a group exists and add if it doesn’t in Linux Shell Script

I am using the Ubuntu virtual machine but all of the results i have found on similar sites do not work.

asked Mar 16 ’15 16:03

annieapple2000

People also ask

Type the command «id -G » to list all the GIDs for a particular user. Replace » » with the user’s Unix or Linux username.

Use the most commonly used “cat” command to get the list of the groups available in the “/etc/group” file. When you run the command, you will get the list of the groups.

We can use the getent command to read the group database to get all groups: $ getent group root:x:0:root bin:x:1:root,bin,daemon daemon:x:2:root,bin,daemon sys:x:3:root,bin adm:x:4:root,daemon tty:x:5: disk:x:6:root lp:x:7:cups,daemon,kent mem:x:8: .

To view all groups present on the system simply open the /etc/group file. Each line in this file represents information for one group. Another option is to use the getent command which displays entries from databases configured in /etc/nsswitch.

1 Answers

The grep statement in the solution of rups has some flaws:

E.g. grepping for a group admin may return true («group exists») when there is a group lpadmin .

Either fix the grep -query

if [ $(getent group admin) ]; then echo "group exists." else echo "group does not exist." fi 

Источник