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



NAME
       uname - get name and information about current kernel

SYNOPSIS
       #include <sys/utsname.h>

       int uname(struct utsname *buf);

DESCRIPTION
       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[];    /* OS release (e.g., "2.6.28") */
               char version[];    /* OS 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
       On success, zero is returned.  On error, -1 is returned, and errno is set appropriately.

ERRORS
       EFAULT buf is not valid.

CONFORMING TO
       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
       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}.

   Underlying kernel interface
       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 ver-
       sion of the system call provided by the kernel.

SEE ALSO
       uname(1), getdomainname(2), gethostname(2)

COLOPHON
       This page is part of release 3.22 of the Linux man-pages project.  A description of the project,  and  informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



Linux                             2008-12-03                          UNAME(2)