Lib/platform.py

#!/usr/bin/env python

""" This module tries to retrieve as much platform-identifying data as
    possible. It makes this information available via function APIs.

    If called from the command line, it prints the platform
    information concatenated as single string to stdout. The output
    format is useable as part of a filename.

"""
#    This module is maintained by Marc-Andre Lemburg <mal@egenix.com>.
#    If you find problems, please submit bug reports/patches via the
#    Python SourceForge Project Page and assign them to "lemburg".
#
#    Note: Please keep this module compatible to Python 1.5.2.
#
#    Still needed:
#    * more support for WinCE
#    * support for MS-DOS (PythonDX ?)
#    * support for Amiga and other still unsupported platforms running Python
#    * support for additional Linux distributions
#
#    Many thanks to all those who helped adding platform-specific
#    checks (in no particular order):
#
#      Charles G Waldman, David Arnold, Gordon McMillan, Ben Darnell,
#      Jeff Bauer, Cliff Crawford, Ivan Van Laningham, Josef
#      Betancourt, Randall Hopper, Karl Putland, John Farrell, Greg
#      Andruk, Just van Rossum, Thomas Heller, Mark R. Levinson, Mark
#      Hammond, Bill Tutt, Hans Nowak, Uwe Zessin (OpenVMS support),
#      Colin Kong, Trent Mick
#
#    History:
#    1.0.1 - reformatted to make doc.py happy
#    1.0.0 - reformatted a bit and checked into Python CVS
#    0.8.0 - added sys.version parser and various new access
#            APIs (python_version(), python_compiler(), etc.)
#    0.7.2 - fixed architecture() to use sizeof(pointer) where available
#    0.7.1 - added support for Caldera OpenLinux
#    0.7.0 - some fixes for WinCE; untabified the source file
#    0.6.2 - support for OpenVMS - requires version 1.5.2-V006 or higher and
#            vms_lib.getsyi() configured
#    0.6.1 - added code to prevent 'uname -p' on platforms which are
#            known not to support it
#    0.6.0 - fixed win32_ver() to hopefully work on Win95,98,NT and Win2k;
#            did some cleanup of the interfaces - some APIs have changed
#    0.5.5 - fixed another type in the MacOS code... should have
#            used more coffee today ;-)
#    0.5.4 - fixed a few typos in the MacOS code
#    0.5.3 - added experimental MacOS support; added better popen()
#            workarounds in _syscmd_ver() -- still not 100% elegant
#            though
#    0.5.2 - fixed uname() to return '' instead of 'unknown' in all
#            return values (the system uname command tends to return
#            'unknown' instead of just leaving the field emtpy)
#    0.5.1 - included code for slackware dist; added exception handlers
#            to cover up situations where platforms don't have os.popen
#            (e.g. Mac) or fail on socket.gethostname(); fixed libc
#            detection RE
#    0.5.0 - changed the API names referring to system commands to *syscmd*;
#            added java_ver(); made syscmd_ver() a private
#            API (was system_ver() in previous versions) -- use uname()
#            instead; extended the win32_ver() to also return processor
#            type information
#    0.4.0 - added win32_ver() and modified the platform() output for WinXX
#    0.3.4 - fixed a bug in _follow_symlinks()
#    0.3.3 - fixed popen() and "file" command invokation bugs
#    0.3.2 - added architecture() API and support for it in platform()
#    0.3.1 - fixed syscmd_ver() RE to support Windows NT
#    0.3.0 - added system alias support
#    0.2.3 - removed 'wince' again... oh well.
#    0.2.2 - added 'wince' to syscmd_ver() supported platforms
#    0.2.1 - added cache logic and changed the platform string format
#    0.2.0 - changed the API to use functions instead of module globals
#            since some action take too long to be run on module import
#    0.1.0 - first release
#
#    You can always get the latest version of this module at:
#
#             http://www.egenix.com/files/python/platform.py
#
#    If that URL should fail, try contacting the author.

__copyright__ = """
    Copyright (c) 1999-2000, Marc-Andre Lemburg; mailto:mal@lemburg.com
    Copyright (c) 2000-2003, eGenix.com Software GmbH; mailto:info@egenix.com

    Permission to use, copy, modify, and distribute this software and its
    documentation for any purpose and without fee or royalty is hereby granted,
    provided that the above copyright notice appear in all copies and that
    both that copyright notice and this permission notice appear in
    supporting documentation or portions thereof, including modifications,
    that you make.

    EGENIX.COM SOFTWARE GMBH DISCLAIMS ALL WARRANTIES WITH REGARD TO
    THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
    FITNESS, IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL,
    INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
    FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
    NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
    WITH THE USE OR PERFORMANCE OF THIS SOFTWARE !

"""

__version__ = '1.0.1'

import sys,string,os,re

### Platform specific APIs

_libc_search = re.compile(r'(__libc_init)'
                          '|'
                          '(GLIBC_([0-9.]+))'
                          '|'
                          '(libc(_\w+)?\.so(?:\.(\d[0-9.]*))?)')

def libc_ver(executable=sys.executable,lib='',version='',

             chunksize=2048):

    """ Tries to determine the libc version that the file executable
        (which defaults to the Python interpreter) is linked against.

        Returns a tuple of strings (lib,version) which default to the
        given parameters in case the lookup fails.

        Note that the function has intimate knowledge of how different
        libc versions add symbols to the executable and thus is probably
        only useable for executables compiled using gcc.

        The file is read and scanned in chunks of chunksize bytes.

    """
    f = open(executable,'rb')
    binary = f.read(chunksize)
    pos = 0
    while 1:
        m = _libc_search.search(binary,pos)
        if not m:
            binary = f.read(chunksize)
            if not binary:
                break
            pos = 0
            continue
        libcinit,glibc,glibcversion,so,threads,soversion = m.groups()
        if libcinit and not lib:
            lib = 'libc'
        elif glibc:
            if lib != 'glibc':
                lib = 'glibc'
                version = glibcversion
            elif glibcversion > version:
                version = glibcversion
        elif so:
            if lib != 'glibc':
                lib = 'libc'
                if soversion > version:
                    version = soversion
                if threads and version[-len(threads):] != threads:
                    version = version + threads
        pos = m.end()
    f.close()
    return lib,version

def _dist_try_harder(distname,version,id):

    """ Tries some special tricks to get the distribution
        information in case the default method fails.

        Currently supports older SuSE Linux, Caldera OpenLinux and
        Slackware Linux distributions.

    """
    if os.path.exists('/var/adm/inst-log/info'):
        # SuSE Linux stores distribution information in that file
        info = open('/var/adm/inst-log/info').readlines()
        distname = 'SuSE'
        for line in info:
            tv = string.split(line)
            if len(tv) == 2:
                tag,value = tv
            else:
                continue
            if tag == 'MIN_DIST_VERSION':
                version = string.strip(value)
            elif tag == 'DIST_IDENT':
                values = string.split(value,'-')
                id = values[2]
        return distname,version,id

    if os.path.exists('/etc/.installed'):
        # Caldera OpenLinux has some infos in that file (thanks to Colin Kong)
        info = open('/etc/.installed').readlines()
        for line in info:
            pkg = string.split(line,'-')
            if len(pkg) >= 2 and pkg[0] == 'OpenLinux':
                # XXX does Caldera support non Intel platforms ? If yes,
                #     where can we find the needed id ?
                return 'OpenLinux',pkg[1],id

    if os.path.isdir('/usr/lib/setup'):
        # Check for slackware verson tag file (thanks to Greg Andruk)
        verfiles = os.listdir('/usr/lib/setup')
        for n in reversed(xrange(len(verfiles))):
            if verfiles[n][:14] != 'slack-version-':
                del verfiles[n]
        if verfiles:
            verfiles.sort()
            distname = 'slackware'
            version = verfiles[-1][14:]
            return distname,version,id

    return distname,version,id

_release_filename = re.compile(r'(\w+)[-_](release|version)')
_release_version = re.compile(r'([\d.]+)[^(]*(?:\((.+)\))?')

def dist(distname='',version='',id='',

         supported_dists=('SuSE','debian','redhat','mandrake')):

    """ Tries to determine the name of the Linux OS distribution name.

        The function first looks for a distribution release file in
        /etc and then reverts to _dist_try_harder() in case no
        suitable files are found.

        Returns a tuple (distname,version,id) which default to the
        args given as parameters.

    """
    try:
        etc = os.listdir('/etc')
    except os.error:
        # Probably not a Unix system
        return distname,version,id
    for file in etc:
        m = _release_filename.match(file)
        if m:
            _distname,dummy = m.groups()
            if _distname in supported_dists:
                distname = _distname
                break
    else:
        return _dist_try_harder(distname,version,id)
    f = open('/etc/'+file,'r')
    firstline = f.readline()
    f.close()
    m = _release_version.search(firstline)
    if m:
        _version,_id = m.groups()
        if _version:
            version = _version
        if _id:
            id = _id
    else:
        # Unkown format... take the first two words
        l = string.split(string.strip(firstline))
        if l:
            version = l[0]
            if len(l) > 1:
                id = l[1]
    return distname,version,id

class _popen:

    """ Fairly portable (alternative) popen implementation.

        This is mostly needed in case os.popen() is not available, or
        doesn't work as advertised, e.g. in Win9X GUI programs like
        PythonWin or IDLE.

        Writing to the pipe is currently not supported.

    """
    tmpfile = ''
    pipe = None
    bufsize = None
    mode = 'r'

    def __init__(self,cmd,mode='r',bufsize=None):

        if mode != 'r':
            raise ValueError,'popen()-emulation only supports read mode'
        import tempfile
        self.tmpfile = tmpfile = tempfile.mktemp()
        os.system(cmd + ' > %s' % tmpfile)
        self.pipe = open(tmpfile,'rb')
        self.bufsize = bufsize
        self.mode = mode

    def read(self):

        return self.pipe.read()

    def readlines(self):

        if self.bufsize is not None:
            return self.pipe.readlines()

    def close(self,

              remove=os.unlink,error=os.error):

        if self.pipe:
            rc = self.pipe.close()
        else:
            rc = 255
        if self.tmpfile:
            try:
                remove(self.tmpfile)
            except error:
                pass
        return rc

    # Alias
    __del__ = close

def popen(cmd, mode='r', bufsize=None):

    """ Portable popen() interface.
    """
    # Find a working popen implementation preferring win32pipe.popen
    # over os.popen over _popen
    popen = None
    if os.environ.get('OS','') == 'Windows_NT':
        # On NT win32pipe should work; on Win9x it hangs due to bugs
        # in the MS C lib (see MS KnowledgeBase article Q150956)
        try:
            import win32pipe
        except ImportError:
            pass
        else:
            popen = win32pipe.popen
    if popen is None:
        if hasattr(os,'popen'):
            popen = os.popen
            # Check whether it works... it doesn't in GUI programs
            # on Windows platforms
            if sys.platform == 'win32': # XXX Others too ?
                try:
                    popen('')
                except os.error:
                    popen = _popen
        else:
            popen = _popen
    if bufsize is None:
        return popen(cmd,mode)
    else:
        return popen(cmd,mode,bufsize)

def _norm_version(version,build=''):

    """ Normalize the version and build strings and return a single
        vesion string using the format major.minor.build (or patchlevel).
    """
    l = string.split(version,'.')
    if build:
        l.append(build)
    try:
        ints = map(int,l)
    except ValueError:
        strings = l
    else:
        strings = map(str,ints)
    version = string.join(strings[:3],'.')
    return version

_ver_output = re.compile(r'(?:([\w ]+) ([\w.]+) '
                         '.*'
                         'Version ([\d.]+))')

def _syscmd_ver(system='',release='',version='',

               supported_platforms=('win32','win16','dos','os2')):

    """ Tries to figure out the OS version used and returns
        a tuple (system,release,version).

        It uses the "ver" shell command for this which is known
        to exists on Windows, DOS and OS/2. XXX Others too ?

        In case this fails, the given parameters are used as
        defaults.

    """
    if sys.platform not in supported_platforms:
        return system,release,version

    # Try some common cmd strings
    for cmd in ('ver','command /c ver','cmd /c ver'):
        try:
            pipe = popen(cmd)
            info = pipe.read()
            if pipe.close():
                raise os.error,'command failed'
            # XXX How can I supress shell errors from being written
            #     to stderr ?
        except os.error,why:
            #print 'Command %s failed: %s' % (cmd,why)
            continue
        except IOError,why:
            #print 'Command %s failed: %s' % (cmd,why)
            continue
        else:
            break
    else:
        return system,release,version

    # Parse the output
    info = string.strip(info)
    m = _ver_output.match(info)
    if m:
        system,release,version = m.groups()
        # Strip trailing dots from version and release
        if release[-1] == '.':
            release = release[:-1]
        if version[-1] == '.':
            version = version[:-1]
        # Normalize the version and build strings (eliminating additional
        # zeros)
        version = _norm_version(version)
    return system,release,version

def _win32_getvalue(key,name,default=''):

    """ Read a value for name from the registry key.

        In case this fails, default is returned.

    """
    from win32api import RegQueryValueEx
    try:
        return RegQueryValueEx(key,name)
    except:
        return default

def win32_ver(release='',version='',csd='',ptype=''):

    """ Get additional version information from the Windows Registry
        and return a tuple (version,csd,ptype) referring to version
        number, CSD level and OS type (multi/single
        processor).

        As a hint: ptype returns 'Uniprocessor Free' on single
        processor NT machines and 'Multiprocessor Free' on multi
        processor machines. The 'Free' refers to the OS version being
        free of debugging code. It could also state 'Checked' which
        means the OS version uses debugging code, i.e. code that
        checks arguments, ranges, etc. (Thomas Heller).

        Note: this function only works if Mark Hammond's win32
        package is installed and obviously only runs on Win32
        compatible platforms.

    """
    # XXX Is there any way to find out the processor type on WinXX ?
    # XXX Is win32 available on Windows CE ?
    # Adapted from code posted by Karl Putland to comp.lang.python.

    # Import the needed APIs
    try:
        import win32api
    except ImportError:
        return release,version,csd,ptype
    from win32api import RegQueryValueEx,RegOpenKeyEx,RegCloseKey,GetVersionEx
    from win32con import HKEY_LOCAL_MACHINE,VER_PLATFORM_WIN32_NT,\
                         VER_PLATFORM_WIN32_WINDOWS

    # Find out the registry key and some general version infos
    maj,min,buildno,plat,csd = GetVersionEx()
    version = '%i.%i.%i' % (maj,min,buildno & 0xFFFF)
    if csd[:13] == 'Service Pack ':
        csd = 'SP' + csd[13:]
    if plat == VER_PLATFORM_WIN32_WINDOWS:
        regkey = 'SOFTWARE\\Microsoft\\Windows\\CurrentVersion'
        # Try to guess the release name
        if maj == 4:
            if min == 0:
                release = '95'
            else:
                release = '98'
        elif maj == 5:
            release = '2000'
    elif plat == VER_PLATFORM_WIN32_NT:
        regkey = 'SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion'
        if maj <= 4:
            release = 'NT'
        elif maj == 5:
            release = '2000'
    else:
        if not release:
            # E.g. Win3.1 with win32s
            release = '%i.%i' % (maj,min)
        return release,version,csd,ptype

    # Open the registry key
    try:
        keyCurVer = RegOpenKeyEx(HKEY_LOCAL_MACHINE,regkey)
        # Get a value to make sure the key exists...
        RegQueryValueEx(keyCurVer,'SystemRoot')
    except:
        return release,version,csd,ptype

    # Parse values
    #subversion = _win32_getvalue(keyCurVer,
    #                            'SubVersionNumber',
    #                            ('',1))[0]
    #if subversion:
    #   release = release + subversion # 95a, 95b, etc.
    build = _win32_getvalue(keyCurVer,
                            'CurrentBuildNumber',
                            ('',1))[0]
    ptype = _win32_getvalue(keyCurVer,
                           'CurrentType',
                           (ptype,1))[0]

    # Normalize version
    version = _norm_version(version,build)

    # Close key
    RegCloseKey(keyCurVer)
    return release,version,csd,ptype

def _mac_ver_lookup(selectors,default=None):

    from gestalt import gestalt
    import MacOS
    l = []
    append = l.append
    for selector in selectors:
        try:
            append(gestalt(selector))
        except (RuntimeError, MacOS.Error):
            append(default)
    return l

def _bcd2str(bcd):

    return hex(bcd)[2:]

def mac_ver(release='',versioninfo=('','',''),machine=''):

    """ Get MacOS version information and return it as tuple (release,
        versioninfo, machine) with versioninfo being a tuple (version,
        dev_stage, non_release_version).

        Entries which cannot be determined are set to the paramter values
        which default to ''. All tuple entries are strings.

        Thanks to Mark R. Levinson for mailing documentation links and
        code examples for this function. Documentation for the
        gestalt() API is available online at:

           http://www.rgaros.nl/gestalt/

    """
    # Check whether the version info module is available
    try:
        import gestalt
        import MacOS
    except ImportError:
        return release,versioninfo,machine
    # Get the infos
    sysv,sysu,sysa = _mac_ver_lookup(('sysv','sysu','sysa'))
    # Decode the infos
    if sysv:
        major = (sysv & 0xFF00) >> 8
        minor = (sysv & 0x00F0) >> 4
        patch = (sysv & 0x000F)
        release = '%s.%i.%i' % (_bcd2str(major),minor,patch)
    if sysu:
        major =  int((sysu & 0xFF000000L) >> 24)
        minor =  (sysu & 0x00F00000) >> 20
        bugfix = (sysu & 0x000F0000) >> 16
        stage =  (sysu & 0x0000FF00) >> 8
        nonrel = (sysu & 0x000000FF)
        version = '%s.%i.%i' % (_bcd2str(major),minor,bugfix)
        nonrel = _bcd2str(nonrel)
        stage = {0x20:'development',
                 0x40:'alpha',
                 0x60:'beta',
                 0x80:'final'}.get(stage,'')
        versioninfo = (version,stage,nonrel)
    if sysa:
        machine = {0x1: '68k',
                   0x2: 'PowerPC'}.get(sysa,'')
    return release,versioninfo,machine

def _java_getprop(name,default):

    from java.lang import System
    try:
        return System.getProperty(name)
    except:
        return default

def java_ver(release='',vendor='',vminfo=('','',''),osinfo=('','','')):

    """ Version interface for Jython.

        Returns a tuple (release,vendor,vminfo,osinfo) with vminfo being
        a tuple (vm_name,vm_release,vm_vendor) and osinfo being a
        tuple (os_name,os_version,os_arch).

        Values which cannot be determined are set to the defaults
        given as parameters (which all default to '').

    """
    # Import the needed APIs
    try:
        import java.lang
    except ImportError:
        return release,vendor,vminfo,osinfo

    vendor = _java_getprop('java.vendor',vendor)
    release = _java_getprop('java.version',release)
    vm_name,vm_release,vm_vendor = vminfo
    vm_name = _java_getprop('java.vm.name',vm_name)
    vm_vendor = _java_getprop('java.vm.vendor',vm_vendor)
    vm_release = _java_getprop('java.vm.version',vm_release)
    vminfo = vm_name,vm_release,vm_vendor
    os_name,os_version,os_arch = osinfo
    os_arch = _java_getprop('java.os.arch',os_arch)
    os_name = _java_getprop('java.os.name',os_name)
    os_version = _java_getprop('java.os.version',os_version)
    osinfo = os_name,os_version,os_arch

    return release,vendor,vminfo,osinfo

### System name aliasing

def system_alias(system,release,version):

    """ Returns (system,release,version) aliased to common
        marketing names used for some systems.

        It also does some reordering of the information in some cases
        where it would otherwise cause confusion.

    """
    if system == 'Rhapsody':
        # Apple's BSD derivative
        # XXX How can we determine the marketing release number ?
        return 'MacOS X Server',system+release,version

    elif system == 'SunOS':
        # Sun's OS
        if release < '5':
            # These releases use the old name SunOS
            return system,release,version
        # Modify release (marketing release = SunOS release - 3)
        l = string.split(release,'.')
        if l:
            try:
                major = int(l[0])
            except ValueError:
                pass
            else:
                major = major - 3
                l[0] = str(major)
                release = string.join(l,'.')
        if release < '6':
            system = 'Solaris'
        else:
            # XXX Whatever the new SunOS marketing name is...
            system = 'Solaris'

    elif system == 'IRIX64':
        # IRIX reports IRIX64 on platforms with 64-bit support; yet it
        # is really a version and not a different platform, since 32-bit
        # apps are also supported..
        system = 'IRIX'
        if version:
            version = version + ' (64bit)'
        else:
            version = '64bit'

    elif system in ('win32','win16'):
        # In case one of the other tricks
        system = 'Windows'

    return system,release,version

### Various internal helpers

def _platform(*args):

    """ Helper to format the platform string in a filename
        compatible format e.g. "system-version-machine".
    """
    # Format the platform string
    platform = string.join(
        map(string.strip,
            filter(len,args)),
        '-')

    # Cleanup some possible filename obstacles...
    replace = string.replace
    platform = replace(platform,' ','_')
    platform = replace(platform,'/','-')
    platform = replace(platform,'\\','-')
    platform = replace(platform,':','-')
    platform = replace(platform,';','-')
    platform = replace(platform,'"','-')
    platform = replace(platform,'(','-')
    platform = replace(platform,')','-')

    # No need to report 'unknown' information...
    platform = replace(platform,'unknown','')

    # Fold '--'s and remove trailing '-'
    while 1:
        cleaned = replace(platform,'--','-')
        if cleaned == platform:
            break
        platform = cleaned
    while platform[-1] == '-':
        platform = platform[:-1]

    return platform

def _node(default=''):

    """ Helper to determine the node name of this machine.
    """
    try:
        import socket
    except ImportError:
        # No sockets...
        return default
    try:
        return socket.gethostname()
    except socket.error:
        # Still not working...
        return default

# os.path.abspath is new in Python 1.5.2:
if not hasattr(os.path,'abspath'):

    def _abspath(path,

                 isabs=os.path.isabs,join=os.path.join,getcwd=os.getcwd,
                 normpath=os.path.normpath):

        if not isabs(path):
            path = join(getcwd(), path)
        return normpath(path)

else:

    _abspath = os.path.abspath

def _follow_symlinks(filepath):

    """ In case filepath is a symlink, follow it until a
        real file is reached.
    """
    filepath = _abspath(filepath)
    while os.path.islink(filepath):
        filepath = os.path.normpath(
            os.path.join(filepath,os.readlink(filepath)))
    return filepath

def _syscmd_uname(option,default=''):

    """ Interface to the system's uname command.
    """
    if sys.platform in ('dos','win32','win16','os2'):
        # XXX Others too ?
        return default
    try:
        f = os.popen('uname %s 2> /dev/null' % option)
    except (AttributeError,os.error):
        return default
    output = string.strip(f.read())
    rc = f.close()
    if not output or rc:
        return default
    else:
        return output

def _syscmd_file(target,default=''):

    """ Interface to the system's file command.

        The function uses the -b option of the file command to have it
        ommit the filename in its output and if possible the -L option
        to have the command follow symlinks. It returns default in
        case the command should fail.

    """
    target = _follow_symlinks(target)
    try:
        f = os.popen('file %s 2> /dev/null' % target)
    except (AttributeError,os.error):
        return default
    output = string.strip(f.read())
    rc = f.close()
    if not output or rc:
        return default
    else:
        return output

### Information about the used architecture

# Default values for architecture; non-empty strings override the
# defaults given as parameters
_default_architecture = {
    'win32': ('','WindowsPE'),
    'win16': ('','Windows'),
    'dos': ('','MSDOS'),
}

_architecture_split = re.compile(r'[\s,]').split

def architecture(executable=sys.executable,bits='',linkage=''):

    """ Queries the given executable (defaults to the Python interpreter
        binary) for various architecture information.

        Returns a tuple (bits,linkage) which contains information about
        the bit architecture and the linkage format used for the
        executable. Both values are returned as strings.

        Values that cannot be determined are returned as given by the
        parameter presets. If bits is given as '', the sizeof(pointer)
        (or sizeof(long) on Python version < 1.5.2) is used as
        indicator for the supported pointer size.

        The function relies on the system's "file" command to do the
        actual work. This is available on most if not all Unix
        platforms. On some non-Unix platforms where the "file" command
        does not exist and the executable is set to the Python interpreter
        binary defaults from _default_architecture are used.

    """
    # Use the sizeof(pointer) as default number of bits if nothing
    # else is given as default.
    if not bits:
        import struct
        try:
            size = struct.calcsize('P')
        except struct.error:
            # Older installations can only query longs
            size = struct.calcsize('l')
        bits = str(size*8) + 'bit'

    # Get data from the 'file' system command
    output = _syscmd_file(executable,'')

    if not output and \
       executable == sys.executable:
        # "file" command did not return anything; we'll try to provide
        # some sensible defaults then...
        if _default_architecture.has_key(sys.platform):
            b,l = _default_architecture[sys.platform]
            if b:
                bits = b
            if l:
                linkage = l
        return bits,linkage

    # Split the output into a list of strings omitting the filename
    fileout = _architecture_split(output)[1:]

    if 'executable' not in fileout:
        # Format not supported
        return bits,linkage

    # Bits
    if '32-bit' in fileout:
        bits = '32bit'
    elif 'N32' in fileout:
        # On Irix only
        bits = 'n32bit'
    elif '64-bit' in fileout:
        bits = '64bit'

    # Linkage
    if 'ELF' in fileout:
        linkage = 'ELF'
    elif 'PE' in fileout:
        # E.g. Windows uses this format
        if 'Windows' in fileout:
            linkage = 'WindowsPE'
        else:
            linkage = 'PE'
    elif 'COFF' in fileout:
        linkage = 'COFF'
    elif 'MS-DOS' in fileout:
        linkage = 'MSDOS'
    else:
        # XXX the A.OUT format also falls under this class...
        pass

    return bits,linkage

### Portable uname() interface

_uname_cache = None

def uname():

    """ Fairly portable uname interface. Returns a tuple
        of strings (system,node,release,version,machine,processor)
        identifying the underlying platform.

        Note that unlike the os.uname function this also returns
        possible processor information as an additional tuple entry.

        Entries which cannot be determined are set to ''.

    """
    global _uname_cache

    if _uname_cache is not None:
        return _uname_cache

    # Get some infos from the builtin os.uname API...
    try:
        system,node,release,version,machine = os.uname()

    except AttributeError:
        # Hmm, no uname... we'll have to poke around the system then.
        system = sys.platform
        release = ''
        version = ''
        node = _node()
        machine = ''
        processor = ''
        use_syscmd_ver = 1

        # Try win32_ver() on win32 platforms
        if system == 'win32':
            release,version,csd,ptype = win32_ver()
            if release and version:
                use_syscmd_ver = 0

        # Try the 'ver' system command available on some
        # platforms
        if use_syscmd_ver:
            system,release,version = _syscmd_ver(system)

        # In case we still don't know anything useful, we'll try to
        # help ourselves
        if system in ('win32','win16'):
            if not version:
                if system == 'win32':
                    version = '32bit'
                else:
                    version = '16bit'
            system = 'Windows'

        elif system[:4] == 'java':
            release,vendor,vminfo,osinfo = java_ver()
            system = 'Java'
            version = string.join(vminfo,', ')
            if not version:
                version = vendor

        elif os.name == 'mac':
            release,(version,stage,nonrel),machine = mac_ver()
            system = 'MacOS'

    else:
        # System specific extensions
        if system == 'OpenVMS':
            # OpenVMS seems to have release and version mixed up
            if not release or release == '0':
                release = version
                version = ''
            # Get processor information
            try:
                import vms_lib
            except ImportError:
                pass
            else:
                csid, cpu_number = vms_lib.getsyi('SYI$_CPU',0)
                if (cpu_number >= 128):
                    processor = 'Alpha'
                else:
                    processor = 'VAX'
        else:
            # Get processor information from the uname system command
            processor = _syscmd_uname('-p','')

    # 'unknown' is not really any useful as information; we'll convert
    # it to '' which is more portable
    if system == 'unknown':
        system = ''
    if node == 'unknown':
        node = ''
    if release == 'unknown':
        release = ''
    if version == 'unknown':
        version = ''
    if machine == 'unknown':
        machine = ''
    if processor == 'unknown':
        processor = ''
    _uname_cache = system,node,release,version,machine,processor
    return _uname_cache

### Direct interfaces to some of the uname() return values

def system():

    """ Returns the system/OS name, e.g. 'Linux', 'Windows' or 'Java'.

        An empty string is returned if the value cannot be determined.

    """
    return uname()[0]

def node():

    """ Returns the computer's network name (which may not be fully
        qualified)

        An empty string is returned if the value cannot be determined.

    """
    return uname()[1]

def release():

    """ Returns the system's release, e.g. '2.2.0' or 'NT'

        An empty string is returned if the value cannot be determined.

    """
    return uname()[2]

def version():

    """ Returns the system's release version, e.g. '#3 on degas'

        An empty string is returned if the value cannot be determined.

    """
    return uname()[3]

def machine():

    """ Returns the machine type, e.g. 'i386'

        An empty string is returned if the value cannot be determined.

    """
    return uname()[4]

def processor():

    """ Returns the (true) processor name, e.g. 'amdk6'

        An empty string is returned if the value cannot be
        determined. Note that many platforms do not provide this
        information or simply return the same value as for machine(),
        e.g.  NetBSD does this.

    """
    return uname()[5]

### Various APIs for extracting information from sys.version

_sys_version_parser = re.compile(r'([\w.+]+)\s*'
                                  '\(#(\d+),\s*([\w ]+),\s*([\w :]+)\)\s*'
                                  '\[([^\]]+)\]?')
_sys_version_cache = None

def _sys_version():

    """ Returns a parsed version of Python's sys.version as tuple
        (version, buildno, builddate, compiler) referring to the Python
        version, build number, build date/time as string and the compiler
        identification string.

        Note that unlike the Python sys.version, the returned value
        for the Python version will always include the patchlevel (it
        defaults to '.0').

    """
    global _sys_version_cache

    if _sys_version_cache is not None:
        return _sys_version_cache
    version, buildno, builddate, buildtime, compiler = \
             _sys_version_parser.match(sys.version).groups()
    buildno = int(buildno)
    builddate = builddate + ' ' + buildtime
    l = string.split(version, '.')
    if len(l) == 2:
        l.append('0')
        version = string.join(l, '.')
    _sys_version_cache = (version, buildno, builddate, compiler)
    return _sys_version_cache

def python_version():

    """ Returns the Python version as string 'major.minor.patchlevel'

        Note that unlike the Python sys.version, the returned value
        will always include the patchlevel (it defaults to 0).

    """
    return _sys_version()[0]

def python_version_tuple():

    """ Returns the Python version as tuple (major, minor, patchlevel)
        of strings.

        Note that unlike the Python sys.version, the returned value
        will always include the patchlevel (it defaults to 0).

    """
    return string.split(_sys_version()[0], '.')

def python_build():

    """ Returns a tuple (buildno, builddate) stating the Python
        build number and date as strings.

    """
    return _sys_version()[1:3]

def python_compiler():

    """ Returns a string identifying the compiler used for compiling
        Python.

    """
    return _sys_version()[3]

### The Opus Magnum of platform strings :-)

_platform_cache = None
_platform_aliased_cache = None

def platform(aliased=0, terse=0):

    """ Returns a single string identifying the underlying platform
        with as much useful information as possible (but no more :).

        The output is intended to be human readable rather than
        machine parseable. It may look different on different
        platforms and this is intended.

        If "aliased" is true, the function will use aliases for
        various platforms that report system names which differ from
        their common names, e.g. SunOS will be reported as
        Solaris. The system_alias() function is used to implement
        this.

        Setting terse to true causes the function to return only the
        absolute minimum information needed to identify the platform.

    """
    global _platform_cache,_platform_aliased_cache

    if not aliased and (_platform_cache is not None):
        return _platform_cache
    elif _platform_aliased_cache is not None:
        return _platform_aliased_cache

    # Get uname information and then apply platform specific cosmetics
    # to it...
    system,node,release,version,machine,processor = uname()
    if machine == processor:
        processor = ''
    if aliased:
        system,release,version = system_alias(system,release,version)

    if system == 'Windows':
        # MS platforms
        rel,vers,csd,ptype = win32_ver(version)
        if terse:
            platform = _platform(system,release)
        else:
            platform = _platform(system,release,version,csd)

    elif system in ('Linux',):
        # Linux based systems
        distname,distversion,distid = dist('')
        if distname and not terse:
            platform = _platform(system,release,machine,processor,
                                 'with',
                                 distname,distversion,distid)
        else:
            # If the distribution name is unknown check for libc vs. glibc
            libcname,libcversion = libc_ver(sys.executable)
            platform = _platform(system,release,machine,processor,
                                 'with',
                                 libcname+libcversion)
    elif system == 'Java':
        # Java platforms
        r,v,vminfo,(os_name,os_version,os_arch) = java_ver()
        if terse:
            platform = _platform(system,release,version)
        else:
            platform = _platform(system,release,version,
                                 'on',
                                 os_name,os_version,os_arch)

    elif system == 'MacOS':
        # MacOS platforms
        if terse:
            platform = _platform(system,release)
        else:
            platform = _platform(system,release,machine)

    else:
        # Generic handler
        if terse:
            platform = _platform(system,release)
        else:
            bits,linkage = architecture(sys.executable)
            platform = _platform(system,release,machine,processor,bits,linkage)

    if aliased:
        _platform_aliased_cache = platform
    elif terse:
        pass
    else:
        _platform_cache = platform
    return platform

### Command line interface

if __name__ == '__main__':
    # Default is to print the aliased verbose platform string
    terse = ('terse' in sys.argv or '--terse' in sys.argv)
    aliased = (not 'nonaliased' in sys.argv and not '--nonaliased' in sys.argv)
    print platform(aliased,terse)
    sys.exit(0)