path: root/Lib/distutils/util.py

"""distutils.util

Miscellaneous utility functions -- anything that doesn't fit into
one of the other *util.py modules.
"""

# created 1999/03/08, Greg Ward

__revision__ = "$Id$"

import sys, os, string, re, shutil
from distutils.errors import *
from distutils.spawn import spawn


def get_platform ():
    """Return a string that identifies the current platform.  This is used
    mainly to distinguish platform-specific build directories and
    platform-specific built distributions.  Typically includes the OS name
    and version and the architecture (as supplied by 'os.uname()'),
    although the exact information included depends on the OS; eg. for IRIX
    the architecture isn't particularly important (IRIX only runs on SGI
    hardware), but for Linux the kernel version isn't particularly
    important.

    Examples of returned values:
       linux-i586
       linux-alpha (?)
       solaris-2.6-sun4u
       irix-5.3
       irix64-6.2
       
    For non-POSIX platforms, currently just returns 'sys.platform'.
    """
    if os.name != "posix" or not hasattr(os, 'uname'):
        # XXX what about the architecture? NT is Intel or Alpha,
        # Mac OS is M68k or PPC, etc.
        return sys.platform

    # Try to distinguish various flavours of Unix

    (osname, host, release, version, machine) = os.uname()
    osname = string.lower(osname)
    if osname[:5] == "linux":
        # At least on Linux/Intel, 'machine' is the processor --
        # i386, etc.
        # XXX what about Alpha, SPARC, etc?
        return  "%s-%s" % (osname, machine)
    elif osname[:5] == "sunos":
        if release[0] >= "5":           # SunOS 5 == Solaris 2
            osname = "solaris"
            release = "%d.%s" % (int(release[0]) - 3, release[2:])
        # fall through to standard osname-release-machine representation
    elif osname[:4] == "irix":              # could be "irix64"!
        return "%s-%s" % (osname, release)
            
    return "%s-%s-%s" % (osname, release, machine)

# get_platform ()


def convert_path (pathname):
    """Return 'pathname' as a name that will work on the native filesystem,
    i.e. split it on '/' and put it back together again using the current
    directory separator.  Needed because filenames in the setup script are
    always supplied in Unix style, and have to be converted to the local
    convention before we can actually use them in the filesystem.  Raises
    ValueError on non-Unix-ish systems if 'pathname' either starts or
    ends with a slash.
    """
    if os.sep == '/':
        return pathname
    if pathname[0] == '/':
        raise ValueError, "path '%s' cannot be absolute" % pathname
    if pathname[-1] == '/':
        raise ValueError, "path '%s' cannot end with '/'" % pathname

    paths = string.split(pathname, '/')
    return apply(os.path.join, paths)

# convert_path ()


def change_root (new_root, pathname):
    """Return 'pathname' with 'new_root' prepended.  If 'pathname' is
    relative, this is equivalent to "os.path.join(new_root,pathname)".
    Otherwise, it requires making 'pathname' relative and then joining the
    two, which is tricky on DOS/Windows and Mac OS.
    """
    if os.name == 'posix':
        if not os.path.isabs(pathname):
            return os.path.join(new_root, pathname)
        else:
            return os.path.join(new_root, pathname[1:])

    elif os.name == 'nt':
        (drive, path) = os.path.splitdrive(pathname)
        if path[0] == '\\':
            path = path[1:]
        return os.path.join(new_root, path)

    elif os.name == 'mac':
        if not os.path.isabs(pathname):
            return os.path.join(new_root, pathname)
        else:
            # Chop off volume name from start of path
            elements = string.split(pathname, ":", 1)
            pathname = ":" + elements[1]
            return os.path.join(new_root, pathname)

    else:
        raise DistutilsPlatformError, \
              "nothing known about platform '%s'" % os.name


_environ_checked = 0
def check_environ ():
    """Ensure that 'os.environ' has all the environment variables we
    guarantee that users can use in config files, command-line options,
    etc.  Currently this includes:
      HOME - user's home directory (Unix only)
      PLAT - description of the current platform, including hardware
             and OS (see 'get_platform()')
    """
    global _environ_checked
    if _environ_checked:
        return

    if os.name == 'posix' and not os.environ.has_key('HOME'):
        import pwd
        os.environ['HOME'] = pwd.getpwuid(os.getuid())[5]

    if not os.environ.has_key('PLAT'):
        os.environ['PLAT'] = get_platform()

    _environ_checked = 1


def subst_vars (str, local_vars):
    """Perform shell/Perl-style variable substitution on 'string'.  Every
    occurrence of '$' followed by a name is considered a variable, and
    variable is substituted by the value found in the 'local_vars'
    dictionary, or in 'os.environ' if it's not in 'local_vars'.
    'os.environ' is first checked/augmented to guarantee that it contains
    certain values: see 'check_environ()'.  Raise ValueError for any
    variables not found in either 'local_vars' or 'os.environ'.
    """
    check_environ()
    def _subst (match, local_vars=local_vars):
        var_name = match.group(1)
        if local_vars.has_key(var_name):
            return str(local_vars[var_name])
        else:
            return os.environ[var_name]

    try:
        return re.sub(r'\$([a-zA-Z_][a-zA-Z_0-9]*)', _subst, str)
    except KeyError, var:
        raise ValueError, "invalid variable '$%s'" % var

# subst_vars ()


def grok_environment_error (exc, prefix="error: "):
    """Generate a useful error message from an EnvironmentError (IOError or
    OSError) exception object.  Handles Python 1.5.1 and 1.5.2 styles, and
    does what it can to deal with exception objects that don't have a
    filename (which happens when the error is due to a two-file operation,
    such as 'rename()' or 'link()'.  Returns the error message as a string
    prefixed with 'prefix'.
    """
    # check for Python 1.5.2-style {IO,OS}Error exception objects
    if hasattr(exc, 'filename') and hasattr(exc, 'strerror'):
        if exc.filename:
            error = prefix + "%s: %s" % (exc.filename, exc.strerror)
        else:
            # two-argument functions in posix module don't
            # include the filename in the exception object!
            error = prefix + "%s" % exc.strerror
    else:
        error = prefix + str(exc[-1])

    return error


# Needed by 'split_quoted()'
_wordchars_re = re.compile(r'[^\\\'\"%s ]*' % string.whitespace)
_squote_re = re.compile(r"'(?:[^'\\]|\\.)*'")
_dquote_re = re.compile(r'"(?:[^"\\]|\\.)*"')

def split_quoted (s):
    """Split a string up according to Unix shell-like rules for quotes and
    backslashes.  In short: words are delimited by spaces, as long as those
    spaces are not escaped by a backslash, or inside a quoted string.
    Single and double quotes are equivalent, and the quote characters can
    be backslash-escaped.  The backslash is stripped from any two-character
    escape sequence, leaving only the escaped character.  The quote
    characters are stripped from any quoted string.  Returns a list of
    words.
    """

    # This is a nice algorithm for splitting up a single string, since it
    # doesn't require character-by-character examination.  It was a little
    # bit of a brain-bender to get it working right, though...

    s = string.strip(s)
    words = []
    pos = 0

    while s:
        m = _wordchars_re.match(s, pos)
        end = m.end()
        if end == len(s):
            words.append(s[:end])
            break

        if s[end] in string.whitespace: # unescaped, unquoted whitespace: now
            words.append(s[:end])       # we definitely have a word delimiter
            s = string.lstrip(s[end:])
            pos = 0

        elif s[end] == '\\':            # preserve whatever is being escaped;
                                        # will become part of the current word
            s = s[:end] + s[end+1:]
            pos = end+1

        else:
            if s[end] == "'":           # slurp singly-quoted string
                m = _squote_re.match(s, end)
            elif s[end] == '"':         # slurp doubly-quoted string
                m = _dquote_re.match(s, end)
            else:
                raise RuntimeError, \
                      "this can't happen (bad char '%c')" % s[end]

            if m is None:
                raise ValueError, \
                      "bad string (mismatched %s quotes?)" % s[end]

            (beg, end) = m.span()
            s = s[:beg] + s[beg+1:end-1] + s[end:]
            pos = m.end() - 2

        if pos >= len(s):
            words.append(s)
            break

    return words

# split_quoted ()


def execute (func, args, msg=None, verbose=0, dry_run=0):
    """Perform some action that affects the outside world (eg.  by writing
    to the filesystem).  Such actions are special because they are disabled
    by the 'dry_run' flag, and announce themselves if 'verbose' is true.
    This method takes care of all that bureaucracy for you; all you have to
    do is supply the function to call and an argument tuple for it (to
    embody the "external action" being performed), and an optional message
    to print.
    """
    # Generate a message if we weren't passed one
    if msg is None:
        msg = "%s%s" % (func.__name__, `args`)
        if msg[-2:] == ',)':        # correct for singleton tuple 
            msg = msg[0:-2] + ')'

    # Print it if verbosity level is high enough
    if verbose:
        print msg

    # And do it, as long as we're not in dry-run mode
    if not dry_run:
        apply(func, args)

# execute()


def strtobool (val):
    """Convert a string representation of truth to true (1) or false (0).
    True values are 'y', 'yes', 't', 'true', 'on', and '1'; false values
    are 'n', 'no', 'f', 'false', 'off', and '0'.  Raises ValueError if
    'val' is anything else.
    """
    val = string.lower(val)
    if val in ('y', 'yes', 't', 'true', 'on', '1'):
        return 1
    elif val in ('n', 'no', 'f', 'false', 'off', '0'):
        return 0
    else:
        raise ValueError, "invalid truth value %s" % `val`