src/nepi/util/environ.py

   1
   2 import os, subprocess, os.path
   3
   4 __all__ =  ["python", "ssh_path"]
   5 __all__ += ["rsh", "tcpdump_path", "sshd_path"]
   6 __all__ += ["execute", "backticks"]
   7
   8 def find_bin(name, extra_path = None):
   9     search = []
  10     if "PATH" in os.environ:
  11         search += os.environ["PATH"].split(":")
  12     for pref in ("/", "/usr/", "/usr/local/"):
  13         for d in ("bin", "sbin"):
  14             search.append(pref + d)
  15     if extra_path:
  16         search += extra_path
  17
  18     for d in search:
  19             try:
  20                 os.stat(d + "/" + name)
  21                 return d + "/" + name
  22             except OSError, e:
  23                 if e.errno != os.errno.ENOENT:
  24                     raise
  25     return None
  26
  27 def find_bin_or_die(name, extra_path = None):
  28     r = find_bin(name)
  29     if not r:
  30         raise RuntimeError(("Cannot find `%s' command, impossible to " +
  31                 "continue.") % name)
  32     return r
  33
  34 ssh_path = find_bin_or_die("ssh")
  35 python_path = find_bin_or_die("python")
  36
  37 # Optional tools
  38 rsh_path = find_bin("rsh")
  39 tcpdump_path = find_bin("tcpdump")
  40 sshd_path = find_bin("sshd")
  41
  42 def execute(cmd):
  43     # FIXME: create a global debug variable
  44     #print "[pid %d]" % os.getpid(), " ".join(cmd)
  45     null = open("/dev/null", "r+")
  46     p = subprocess.Popen(cmd, stdout = null, stderr = subprocess.PIPE)
  47     out, err = p.communicate()
  48     if p.returncode != 0:
  49         raise RuntimeError("Error executing `%s': %s" % (" ".join(cmd), err))
  50
  51 def backticks(cmd):
  52     p = subprocess.Popen(cmd, stdout = subprocess.PIPE,
  53             stderr = subprocess.PIPE)
  54     out, err = p.communicate()
  55     if p.returncode != 0:
  56         raise RuntimeError("Error executing `%s': %s" % (" ".join(cmd), err))
  57     return out
  58
  59 def homepath(path, app='.nepi', mode = 0500, directory = False):
  60     home = os.environ.get('HOME')
  61     if home is None:
  62         home = os.path.join(os.sep, 'home', os.getlogin())
  63
  64     path = os.path.join(home, app, path)
  65     if directory:
  66         dirname = path
  67     else:
  68         dirname = os.path.dirname(path)
  69     if not os.path.exists(dirname):
  70         os.makedirs(dirname)
  71
  72     return path
  73
  74 def find_testbed(testbed_id):
  75     mod_name = None
  76
  77     # look for environment-specified testbeds
  78     if 'NEPI_TESTBEDS' in os.environ:
  79         try:
  80             # parse testbed map
  81             #   split space-separated items, filter empty items
  82             testbed_map = filter(bool,os.environ['NEPI_TESTBEDS'].strip().split(' '))
  83             #   split items, keep pairs only, build map
  84             testbed_map = dict([map(str.strip,i.split(':',1)) for i in testbed_map if ':' in i])
  85         except:
  86             import traceback, sys
  87             traceback.print_exc(file=sys.stderr)
  88
  89             # ignore malformed environment
  90             testbed_map = {}
  91
  92         mod_name = testbed_map.get(testbed_id)
  93
  94     if mod_name is None:
  95         # no explicit map, load built-in testbeds
  96         mod_name = "nepi.testbeds.%s" % (testbed_id.lower())
  97
  98     return mod_name
  99