getlogin(2) - NetBSD Manual Pages

GETLOGIN(2)               NetBSD Programmer's Manual               GETLOGIN(2)


NAME

     getlogin, setlogin - get/set login name


LIBRARY

     Standard C Library (libc, -lc)


SYNOPSIS

     #include <unistd.h>

     char *
     getlogin(void);

     int
     setlogin(const char *name);


DESCRIPTION

     The getlogin() routine returns the login name of the user associated with
     the current session, as previously set by setlogin().  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.)

     setlogin() 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 in-
     voked).


RETURN VALUES

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


ERRORS

     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 <sys/param.h>)
                   characters, currently 16.

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


SEE ALSO

     setsid(2)


STANDARDS

     The getlogin() function conforms to IEEE Std 1003.1-1990 (``POSIX'').


HISTORY

     The getlogin() function first appeared in 4.4BSD.


BUGS

     Login names are limited in length by setlogin().  However, lower limits
     are placed on login names elsewhere in the system (UT_NAMESIZE in
     <utmp.h>).

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

NetBSD 1.6                       June 9, 1993                                2