uname(2) — Linux manual page


uname(2)                   System Calls Manual                  uname(2)

NAME         top

       uname - get name and information about current kernel

LIBRARY         top

       Standard C library (libc, -lc)

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 communications network
                                     to which the node is attached, if any */
               char release[];    /* Operating system release
                                     (e.g., "2.6.28") */
               char version[];    /* Operating system version */
               char machine[];    /* Hardware type identifier */
           #ifdef _GNU_SOURCE
               char domainname[]; /* NIS or YP domain name */

       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 to indicate the error.

ERRORS         top

       EFAULT buf is not valid.

VERSIONS         top

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

       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(...).  SVr4 uses 257, "to support Internet hostnames" —
       this is the largest value likely to be encountered in the wild.

STANDARDS         top


HISTORY         top

       POSIX.1-2001, SVr4, 4.4BSD.

   C library/kernel 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.

NOTES         top

       The kernel has the name, release, version, and supported machine
       type built in.  Conversely, the nodename field is configured by
       the administrator to match the network (this is what the BSD
       historically calls the "hostname", and is set via
       sethostname(2)).  Similarly, the domainname field is set via

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

SEE ALSO         top

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

COLOPHON         top

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Linux man-pages 6.9.1          2024-06-15                       uname(2)

Pages that refer to this page: arch(1)systemd-nspawn(1)uname(1)getdomainname(2)gethostname(2)personality(2)syscalls(2)kbuffer_alloc(3)core(5)org.freedesktop.hostname1(5)systemd.exec(5)systemd.unit(5)lvmsystemid(7)signal-safety(7)uts_namespaces(7)modprobe(8)sm-notify(8)systemd-sysext(8)