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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
uname — return system name
SYNOPSIS
uname [−amnrsv]
DESCRIPTION
By default, the uname utility shall write the operating system name to standard output. When options are
specified, symbols representing one or more system characteristics shall be written to the standard
output. The format and contents of the symbols are implementation-defined. On systems conforming to the
System Interfaces volume of POSIX.1‐2008, the symbols written shall be those supported by the uname()
function as defined in the System Interfaces volume of POSIX.1‐2008.
OPTIONS
The uname utility shall conform to the Base Definitions volume of POSIX.1‐2008, Section 12.2, Utility
Syntax Guidelines.
The following options shall be supported:
−a Behave as though all of the options −mnrsv were specified.
−m Write the name of the hardware type on which the system is running to standard output.
−n Write the name of this node within an implementation-defined communications network.
−r Write the current release level of the operating system implementation.
−s Write the name of the implementation of the operating system.
−v Write the current version level of this release of the operating system implementation.
If no options are specified, the uname utility shall write the operating system name, as if the −s option
had been specified.
OPERANDS
None.
STDIN
Not used.
INPUT FILES
None.
ENVIRONMENT VARIABLES
The following environment variables shall affect the execution of uname:
LANG Provide a default value for the internationalization variables that are unset or null. (See the
Base Definitions volume of POSIX.1‐2008, 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
By default, the output shall be a single line of the following form:
"%s\n", <sysname>
If the −a option is specified, the output shall be a single line of the following form:
"%s %s %s %s %s\n", <sysname>, <nodename>, <release>,
<version>, <machine>
Additional implementation-defined symbols may be written; all such symbols shall be written at the end of
the line of output before the <newline>.
If options are specified to select different combinations of the symbols, only those symbols shall be
written, in the order shown above for the −a option. If a symbol is not selected for writing, its
corresponding trailing <blank> characters also shall not be written.
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 The requested information was successfully written.
>0 An error occurred.
CONSEQUENCES OF ERRORS
Default.
The following sections are informative.
APPLICATION USAGE
Note that any of the symbols could include embedded <space> characters, which may affect parsing
algorithms if multiple options are selected for output.
The node name is typically a name that the system uses to identify itself for inter-system communication
addressing.
EXAMPLES
The following command:
uname −sr
writes the operating system name and release level, separated by one or more <blank> characters.
RATIONALE
It was suggested that this utility cannot be used portably since the format of the symbols is
implementation-defined. The POSIX.1 working group could not achieve consensus on defining these formats
in the underlying uname() function, and there was no expectation that this volume of POSIX.1‐2008 would
be any more successful. Some applications may still find this historical utility of value. For example,
the symbols could be used for system log entries or for comparison with operator or user input.
FUTURE DIRECTIONS
None.
SEE ALSO
The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment Variables, Section 12.2, Utility
Syntax Guidelines
The System Interfaces volume of POSIX.1‐2008, uname()
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition,
Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers, Inc
and The Open Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/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 .