getlogin(3C)						   Standard C Library Functions 					      getlogin(3C)

NAME

       getlogin, getlogin_r - get login name

SYNOPSIS

       #include <unistd.h>

       char *getlogin(void);

       char *getlogin_r(char *name, int namelen);

   Standard conforming
       cc [ flag ... ] file... -D_POSIX_PTHREAD_SEMANTICS [ library ... ]

       int getlogin_r(char *name, size_t namesize);

DESCRIPTION

       The  getlogin() function returns a pointer to the login name as found in /var/adm/utmpx. It can be used in conjunction with getpwnam(3C) to
       locate the correct password file entry when the same user ID is shared by several login names.

       If getlogin() is called within a process that is not attached to a terminal, it returns a null pointer. The correct procedure for determin-
       ing the login name is to call cuserid(3C), or to call getlogin() and if it fails to call getpwuid(3C).

       The  getlogin_r() function has the same functionality as getlogin() except that the caller must supply a buffer name with length namelen to
       store the result.  The name buffer must be at least _POSIX_LOGIN_NAME_MAX bytes in size (defined in <limits.h>).  The  POSIX  version  (see
       standards(5)) of getlogin_r() takes a namesize parameter of type size_t.

RETURN VALUES

       Upon  successful  completion,  getlogin()  returns  a pointer to the login name or a null pointer if the user's login name cannot be found.
       Otherwise it returns a null pointer and sets errno to indicate the error.

       The standard-conforming getlogin_r() returns 0 if successful, or the error number upon failure.

ERRORS

       The getlogin_r() function will fail if:

       ERANGE	       The size of the buffer is smaller than the result to be returned.

       EINVAL	       And entry for the current user was not found in the /var/adm/utmpx file.

       The getlogin() and getlogin_r() functions may fail if:

       EMFILE	       There are {OPEN_MAX} file descriptors currently open in the calling process.

       ENFILE	       The maximum allowable number of files is currently open in the system.

       ENXIO	       The calling process has no controlling terminal.

       The getlogin_r() function may fail if:

       ERANGE	       The size of the buffer is smaller than the result to be returned.

USAGE

       The return value of getlogin() points to thread-specific data whose content is overwritten on each call by the same thread.

       Three names associated with the current process can be determined: getpwuid(geteuid()) returns the name associated with the effective  user
       ID  of the process; getlogin() returns the name associated with the current login activity; and getpwuid(getuid()) returns the name associ-
       ated with the real user ID of the process.

FILES

       /var/adm/utmpx	       user access and administration information

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |See below.		   |
       +-----------------------------+-----------------------------+

SEE ALSO

       geteuid(2), getuid(2), cuserid(3C), getgrnam(3C), getpwnam(3C), getpwuid(3C), utmpx(4), attributes(5), standards(5)

NOTES

       When compiling multithreaded programs, see Intro(3).

       The getlogin() function is safe to use in multithreaded applications, but is discouraged. The getlogin_r() function should be used instead.

       Solaris 2.4 and earlier releases provided a getlogin_r() as specified in POSIX.1c Draft 6. The final POSIX.1c standard changed  the  inter-
       face  as described above. Support for the Draft 6 interface is provided for compatibility only and may not be supported in future releases.
       New applications and libraries should use the standard-conforming interface.

SunOS 5.10							    18 May 2004 						      getlogin(3C)