getlogin

getlogin is a function in POSIX-compliant operating systems that returns the name of the user logged in on the controlling terminal of the calling process. It is part of the standard C library. The function typically reads the username from the environment variable LOGNAME. If LOGNAME is not set, it may fall back to other methods, such as reading from the /etc/passwd file.

The getlogin function is often used to identify the current user for logging purposes, access control, or displaying user-specific information. It is important to note that getlogin is not the most secure way to determine a user's identity, especially in scenarios where security is paramount. For more robust user authentication and authorization, system administrators should consider using other system calls or libraries.

The return value of getlogin is a pointer to a null-terminated string containing the username. This pointer may point to static storage that can be overwritten by subsequent calls to getlogin or other functions that modify the same storage. Therefore, it is recommended to copy the returned username if it needs to be preserved. The function returns NULL if the user cannot be determined.