Lib/commands.py

   1 """Execute shell commands via os.popen() and return status, output.
   2
   3 Interface summary:
   4
   5        import commands
   6
   7        outtext = commands.getoutput(cmd)
   8        (exitstatus, outtext) = commands.getstatusoutput(cmd)
   9        outtext = commands.getstatus(file)  # returns output of "ls -ld file"
  10
  11 A trailing newline is removed from the output string.
  12
  13 Encapsulates the basic operation:
  14
  15       pipe = os.popen('{ ' + cmd + '; } 2>&1', 'r')
  16       text = pipe.read()
  17       sts = pipe.close()
  18
  19  [Note:  it would be nice to add functions to interpret the exit status.]
  20 """
  21 from warnings import warnpy3k
  22 warnpy3k("the commands module has been removed in Python 3.0; "
  23          "use the subprocess module instead", stacklevel=2)
  24 del warnpy3k
  25
  26 __all__ = ["getstatusoutput","getoutput","getstatus"]
  27
  28 # Module 'commands'
  29 #
  30 # Various tools for executing commands and looking at their output and status.
  31 #
  32 # NB This only works (and is only relevant) for UNIX.
  33
  34
  35 # Get 'ls -l' status for an object into a string
  36 #
  37 def getstatus(file):
  38     """Return output of "ls -ld <file>" in a string."""
  39     import warnings
  40     warnings.warn("commands.getstatus() is deprecated", DeprecationWarning, 2)
  41     return getoutput('ls -ld' + mkarg(file))
  42
  43
  44 # Get the output from a shell command into a string.
  45 # The exit status is ignored; a trailing newline is stripped.
  46 # Assume the command will work with '{ ... ; } 2>&1' around it..
  47 #
  48 def getoutput(cmd):
  49     """Return output (stdout or stderr) of executing cmd in a shell."""
  50     return getstatusoutput(cmd)[1]
  51
  52
  53 # Ditto but preserving the exit status.
  54 # Returns a pair (sts, output)
  55 #
  56 def getstatusoutput(cmd):
  57     """Return (status, output) of executing cmd in a shell."""
  58     import os
  59     pipe = os.popen('{ ' + cmd + '; } 2>&1', 'r')
  60     text = pipe.read()
  61     sts = pipe.close()
  62     if sts is None: sts = 0
  63     if text[-1:] == '\n': text = text[:-1]
  64     return sts, text
  65
  66
  67 # Make command argument from directory and pathname (prefix space, add quotes).
  68 #
  69 def mk2arg(head, x):
  70     import os
  71     return mkarg(os.path.join(head, x))
  72
  73
  74 # Make a shell command argument from a string.
  75 # Return a string beginning with a space followed by a shell-quoted
  76 # version of the argument.
  77 # Two strategies: enclose in single quotes if it contains none;
  78 # otherwise, enclose in double quotes and prefix quotable characters
  79 # with backslash.
  80 #
  81 def mkarg(x):
  82     if '\'' not in x:
  83         return ' \'' + x + '\''
  84     s = ' "'
  85     for c in x:
  86         if c in '\\$"`':
  87             s = s + '\\'
  88         s = s + c
  89     s = s + '"'
  90     return s