public/subjects/devops/check-user

Check User

Instructions

In this exercise you will make a script check-user.sh that will take 2 arguments and return information about the selected user, always ended by a new line.

The first argument will be a flag defining the behavior of the script:

• -e: check if the user exists, returns yes or no appropriately.
• -i: returns information about the user.

The second argument will be the name of the checked user.

The information about the user will be formatted in the same way it appears in /etc/passwd.

Usage

$ ./check-user.sh -e root
yes
$ ./check-user.sh -i root
root:x:0:0:root:/root:/bin/bash
$ ./check-user.sh -e unknown
no
$ ./check-user.sh -i unknown
$

Your results may appear slightly different.

Error handling

All errors will print a specific message on stderr (ending with a newline) and returns a specific non-zero value:

• Wrong number of arguments: "Error: expect 2 arguments", exit with 1.
• First argument different from -e or -i: "Error: unknown flag", exit with 1.

Hints

• getent is a command to get entries from a database. passwd is the database where information about users is stored.
• getent passwd will give you the list of all users.
• getent passwd <username> will give you information about a specific user.
• If the user doesn't exists getent returns an empty string, use this at your advantage for -e flag.

man getent will provide extensive documentation about this command.

Resources

List Linux users