GETLOGIN(2) BSD System Calls Manual GETLOGIN(2)

NAME
     ggeettllooggiinn, sseettllooggiinn - get/set login name

SYNOPSIS
     ##iinncclluuddee <>

     char *
     ggeettllooggiinn(void);

     int
     sseettllooggiinn(const char *name);

DESCRIPTION
     The ggeettllooggiinn() routine returns the login name of the user associated with
     the current session, as previously set by sseettllooggiinn().  The name is nor-
     mally associated with a login shell at the time a session is created, and
     is inherited by all processes descended from the login shell.  (This is
     true even if some of those processes assume another user ID, for example
     when su(1) is used.)

     SSeettllooggiinn() sets the login name of the user associated with the current
     session to name.  This call is restricted to the super-user, and is nor-
     mally used only when a new session is being created on behalf of the
     named user (for example, at login time, or when a remote shell is
     invoked).

RETURN VALUES
     If a call to ggeettllooggiinn() succeeds, it returns a pointer to a null-termi-
     nated string in a static buffer.  If the name has not been set, it
     returns NULL.  If a call to sseettllooggiinn() succeeds, a value of 0 is
     returned.  If sseettllooggiinn() fails, a value of -1 is returned and an error
     code is placed in the global location errno.

EERRRROORRSS
     The following errors may be returned by these calls:

     [EFAULT]           The name parameter gave an invalid address.

     [EINVAL]           The name parameter pointed to a string that was too
                        long.  Login names are limited to MAXLOGNAME (from
                        ) characters, currently 12.

     [EPERM]            The caller tried to set the login name and was not the
                        super-user.

SEE ALSO
     setsid(2)

BUGS
     Login names are limited in length by sseettllooggiinn().  However, lower limits
     are placed on login names elsewhere in the system (UTNAMESIZE in
     ).

     In earlier versions of the system, ggeettllooggiinn() failed unless the process
     was associated with a login terminal.  The current implementation (using
     sseettllooggiinn()) allows getlogin to succeed even when the process has no con-
     trolling terminal.  In earlier versions of the system, the value returned
     by ggeettllooggiinn() could not be trusted without checking the user ID.  Porta-
     ble programs should probably still make this check.

HISTORY     The ggeettllooggiinn() function first appeared in 4.4BSD.

4.2 Berkeley Distribution        June 9, 1993        4.2 Berkeley Distribution