# logname

## 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.
    


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