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PROLOG
       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.


NAME
       logname — return the user's login name


SYNOPSIS
       logname


DESCRIPTION
       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.


OPTIONS
       None.


OPERANDS
       None.


STDIN
       Not used.


INPUT FILES
       None.


ENVIRONMENT VARIABLES
       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,   Section   8.2,
                 Internationalization   Variables  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.


ASYNCHRONOUS EVENTS
       Default.


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

           "%s\n", <login name>


STDERR
       The standard error shall be used only for diagnostic messages.


OUTPUT FILES
       None.


EXTENDED DESCRIPTION
       None.


EXIT STATUS
       The following exit values shall be returned:

        0    Successful completion.

       >0    An error occurred.


CONSEQUENCES OF ERRORS
       Default.

       The following sections are informative.


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


EXAMPLES
       None.


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


FUTURE DIRECTIONS
       None.


SEE ALSO
       id, who

       The Base Definitions volume of POSIX.1‐2017, Chapter 8, Environment Variables

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


COPYRIGHT
       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 .