logname - return the user's login name
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.1-2008. 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:
- Provide a default value for the internationalization variables that are unset or null. (See XBD Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.)
- If set to a non-empty string value, override the values of all the other internationalization variables.
- 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).
- Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error.
- [XSI] Determine the location of message catalogs for the processing of LC_MESSAGES.
The logname utility output shall be a single line consisting of the user's login name:"%s\n", <login name>
The standard error shall be used only for diagnostic messages.
The following exit values shall be returned:
- Successful completion.
- An error occurred.
The logname utility explicitly ignores the LOGNAME environment variable because environment changes could produce erroneous results.
The passwd file is not listed as required because the implementation may have other means of mapping login names.
XBD Environment Variables
First released in Issue 2.
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