Get User ID (UID) on Linux using C++

In the Linux system, every user is recognized by a unique identifier referred to as a user ID or UID. This identifier plays a crucial role in determining the system resources accessible to each user. This tutorial explains how to get user ID (UID) on Linux using C++.

Current user

The provided code snippet can be used to retrieve the UID of the current user in a Linux environment by utilizing the getuid function:

#include <iostream>
#include <unistd.h>

int main()
{
    unsigned int uid = getuid();

    std::cout << uid << std::endl;

    return 0;
}

Other user

The following code can be used to get the UID of a specified user (www-data in this case) in a Linux environment. The getpwnam function is utilized to retrieve the user account information by username. This function returns the passwd structure from which UID can be extracted.

#include <iostream>
#include <pwd.h>

int main()
{
    const char *username = "www-data";
    passwd *pwd = getpwnam(username);
    unsigned int uid = pwd->pw_uid;

    std::cout << uid << std::endl;

    return 0;
}