The Open Group Base Specifications Issue 7, 2018 edition
IEEE Std 1003.1-2017 (Revision of IEEE Std 1003.1-2008)
Copyright © 2001-2018 IEEE and The Open Group


uname - get the name of the current system


#include <sys/utsname.h>

int uname(struct utsname *


The uname() function shall store information identifying the current system in the structure pointed to by name.

The uname() function uses the utsname structure defined in <sys/utsname.h>.

The uname() function shall return a string naming the current system in the character array sysname. Similarly, nodename shall contain the name of this node within an implementation-defined communications network. The arrays release and version shall further identify the operating system. The array machine shall contain a name that identifies the hardware that the system is running on.

The format of each member is implementation-defined.


Upon successful completion, a non-negative value shall be returned. Otherwise, -1 shall be returned and errno set to indicate the error.


No errors are defined.

The following sections are informative.




The inclusion of the nodename member in this structure does not imply that it is sufficient information for interfacing to communications networks.


The values of the structure members are not constrained to have any relation to the version of this volume of POSIX.1-2017 implemented in the operating system. An application should instead depend on _POSIX_VERSION and related constants defined in <unistd.h>.

This volume of POSIX.1-2017 does not define the sizes of the members of the structure and permits them to be of different sizes, although most implementations define them all to be the same size: eight bytes plus one byte for the string terminator. That size for nodename is not enough for use with many networks.

The uname() function originated in System III, System V, and related implementations, and it does not exist in Version 7 or 4.3 BSD. The values it returns are set at system compile time in those historical implementations.

4.3 BSD has gethostname() and gethostid(), which return a symbolic name and a numeric value, respectively. There are related sethostname() and sethostid() functions that are used to set the values the other two functions return. The former functions are included in this specification, the latter are not.




XBD <sys/utsname.h>


First released in Issue 1. Derived from Issue 1 of the SVID.

End of informative text.


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