This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface

       The logname utility explicitly ignores the LOGNAME environment variable because environment changes could
       produce erroneous results.

       Default.

       Default.

       Thefollowingsectionsareinformative.

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
       for Information  Technology  --  Portable  Operating  System  Interface  (POSIX),  The  Open  Group  Base
       Specifications  Issue  7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics
       Engineers, Inc and The Open Group.  In the event of any discrepancy between this version and the original
       IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee  document.
       The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

       Any  typographical  or formatting errors that appear in this page are most likely to have been introduced
       during  the  conversion  of  the  source  files  to  man  page  format.  To  report  such   errors,   see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                                   2017                                       LOGNAME(1POSIX)

       The  logname  utility  shall  write the user's login name to standard output. The login name shall be the
       string that would be returned by the getlogin() function defined  in  the  System  Interfaces  volume  of
       POSIX.1‐2017.  Under  the  conditions where the getlogin() function would fail, the logname utility shall
       write a diagnostic message to standard error and exit with a non-zero exit status.

       The following environment variables shall affect the execution of logname:

       LANG      Provide a default value for the internationalization variables that are unset or null. (See the
                 Base Definitions volume of POSIX.1‐2017, Section8.2, InternationalizationVariables  for  the
                 precedence   of   internationalization  variables  used  to  determine  the  values  of  locale
                 categories.)

       LC_ALL    If set to a non-empty string value, override the values of all the  other  internationalization
                 variables.

       LC_CTYPE  Determine  the  locale  for the interpretation of sequences of bytes of text data as characters
                 (for example, single-byte as opposed to multi-byte characters in arguments).

       LC_MESSAGES
                 Determine the locale that should be used to  affect  the  format  and  contents  of  diagnostic
                 messages written to standard error.

       NLSPATH   Determine the location of message catalogs for the processing of LC_MESSAGES.

       None.

       The following exit values shall be returned:

        0    Successful completion.

       >0    An error occurred.

       None.

       None.

       None.

       logname — return the user's login name

       None.

       None.

       None.

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of this interface
       may differ (consult the corresponding Linux manual page for details of Linux behavior), or the  interface
       may not be implemented on Linux.

       The  passwd  file  is  not  listed as required because the implementation may have other means of mapping
       login names.

id, who

       The Base Definitions volume of POSIX.1‐2017, Chapter8, EnvironmentVariables

       The System Interfaces volume of POSIX.1‐2017, getlogin()

       The standard error shall be used only for diagnostic messages.

       Not used.

       The logname utility output shall be a single line consisting of the user's login name:

           "%s\n", <loginname>

       logname