Lib/commands.py

   1 # Module 'commands'
   2 #
   3 # Various tools for executing commands and looking at their output and status.
   4 #
   5 # NB This only works (and is only relevant) for UNIX.
   6
   7
   8 # Get 'ls -l' status for an object into a string
   9 #
  10 def getstatus(file):
  11         return getoutput('ls -ld' + mkarg(file))
  12
  13
  14 # Get the output from a shell command into a string.
  15 # The exit status is ignored; a trailing newline is stripped.
  16 # Assume the command will work with '{ ... ; } 2>&1' around it..
  17 #
  18 def getoutput(cmd):
  19         return getstatusoutput(cmd)[1]
  20
  21
  22 # Ditto but preserving the exit status.
  23 # Returns a pair (sts, output)
  24 #
  25 def getstatusoutput(cmd):
  26         import os
  27         pipe = os.popen('{ ' + cmd + '; } 2>&1', 'r')
  28         text = pipe.read()
  29         sts = pipe.close()
  30         if sts == None: sts = 0
  31         if text[-1:] == '\n': text = text[:-1]
  32         return sts, text
  33
  34
  35 # Make command argument from directory and pathname (prefix space, add quotes).
  36 #
  37 def mk2arg(head, x):
  38         import os
  39         return mkarg(os.path.join(head, x))
  40
  41
  42 # Make a shell command argument from a string.
  43 # Two strategies: enclose in single quotes if it contains none;
  44 # otherwise, enclose in double quotes and prefix quotable characters
  45 # with backslash.
  46 #
  47 def mkarg(x):
  48         if '\'' not in x:
  49                 return ' \'' + x + '\''
  50         s = ' "'
  51         for c in x:
  52                 if c in '\\$"`':
  53                         s = s + '\\'
  54                 s = s + c
  55         s = s + '"'
  56         return s