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);

  POSIX
     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 may 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 determining 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 get-
     login()  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 POSIX getlogin_r() returns 0 if successful, or the error
     number upon failure.

ERRORS
     The getlogin() function may fail if:

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

     ENFILE

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Standard C Library Functions                         getlogin(3C)

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

     ENXIO The calling process has no controlling terminal.

     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.

USAGE
     The return value may point to static data whose  content  is
     overwritten by each call.

     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 associated 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  attri-
     butes:

     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | MT-Level                    | See NOTES 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),  Notes
     On Multithreaded Applications.

     The getlogin() function is unsafe in multithreaded  applica-
     tions.  The getlogin_r() function should be used instead.

SunOS 5.8           Last change: 27 Oct 1998                    2

Standard C Library Functions                         getlogin(3C)

     Solaris 2.4 and earlier releases provided a getlogin_r()  as
     specified  in  POSIX.1c Draft 6. The final POSIX.1c standard
     changed the interface 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 POSIX standard interface.

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