NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | NOTES | SEE ALSO | COLOPHON

UNAME(2)                  Linux Programmer's Manual                 UNAME(2)

NAME         top

       uname - get name and information about current kernel

SYNOPSIS         top

       #include <sys/utsname.h>

       int uname(struct utsname *buf);

DESCRIPTION         top

       uname() returns system information in the structure pointed to by
       buf.  The utsname struct is defined in <sys/utsname.h>:

           struct utsname {
               char sysname[];    /* Operating system name (e.g., "Linux") */
               char nodename[];   /* Name within "some implementation-defined
                                     network" */
               char release[];    /* Operating system release (e.g., "2.6.28") */
               char version[];    /* Operating system version */
               char machine[];    /* Hardware identifier */
           #ifdef _GNU_SOURCE
               char domainname[]; /* NIS or YP domain name */
           #endif
           };

       The length of the arrays in a struct utsname is unspecified (see
       NOTES); the fields are terminated by a null byte ('\0').

RETURN VALUE         top

       On success, zero is returned.  On error, -1 is returned, and errno is
       set appropriately.

ERRORS         top

       EFAULT buf is not valid.

CONFORMING TO         top

       SVr4, POSIX.1-2001.  There is no uname() call in 4.3BSD.

       The domainname member (the NIS or YP domain name) is a GNU extension.

NOTES         top

       This is a system call, and the operating system presumably knows its
       name, release and version.  It also knows what hardware it runs on.
       So, four of the fields of the struct are meaningful.  On the other
       hand, the field nodename is meaningless: it gives the name of the
       present machine in some undefined network, but typically machines are
       in more than one network and have several names.  Moreover, the
       kernel has no way of knowing about such things, so it has to be told
       what to answer here.  The same holds for the additional domainname
       field.

       To this end, Linux uses the system calls sethostname(2) and
       setdomainname(2).  Note that there is no standard that says that the
       hostname set by sethostname(2) is the same string as the nodename
       field of the struct returned by uname() (indeed, some systems allow a
       256-byte hostname and an 8-byte nodename), but this is true on Linux.
       The same holds for setdomainname(2) and the domainname field.

       The length of the fields in the struct varies.  Some operating
       systems or libraries use a hardcoded 9 or 33 or 65 or 257.  Other
       systems use SYS_NMLN or _SYS_NMLN or UTSLEN or _UTSNAME_LENGTH.
       Clearly, it is a bad idea to use any of these constants; just use
       sizeof(...).  Often 257 is chosen in order to have room for an
       internet hostname.

       Part of the utsname information is also accessible via
       /proc/sys/kernel/{ostype, hostname, osrelease, version, domainname}.

   C library/kernel ABI differences
       Over time, increases in the size of the utsname structure have led to
       three successive versions of uname(): sys_olduname() (slot
       __NR_oldolduname), sys_uname() (slot __NR_olduname), and
       sys_newuname() (slot __NR_uname).  The first one used length 9 for
       all fields; the second used 65; the third also uses 65 but adds the
       domainname field.  The glibc uname() wrapper function hides these
       details from applications, invoking the most recent version of the
       system call provided by the kernel.

SEE ALSO         top

       uname(1), getdomainname(2), gethostname(2), namespaces(7)

COLOPHON         top

       This page is part of release 3.75 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at
       http://www.kernel.org/doc/man-pages/.

Linux                            2014-09-21                         UNAME(2)