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 

    22 __all__ = ["getstatusoutput","getoutput","getstatus"]

    23 

    24 # Module 'commands'

    25 #

    26 # Various tools for executing commands and looking at their output and status.

    27 #

    28 # NB This only works (and is only relevant) for UNIX.

    29 

    30 

    31 # Get 'ls -l' status for an object into a string

    32 #

    33 def getstatus(file):

    34     """Return output of "ls -ld <file>" in a string."""

    35     return getoutput('ls -ld' + mkarg(file))

    36 

    37 

    38 # Get the output from a shell command into a string.

    39 # The exit status is ignored; a trailing newline is stripped.

    40 # Assume the command will work with '{ ... ; } 2>&1' around it..

    41 #

    42 def getoutput(cmd):

    43     """Return output (stdout or stderr) of executing cmd in a shell."""

    44     return getstatusoutput(cmd)[1]

    45 

    46 

    47 # Ditto but preserving the exit status.

    48 # Returns a pair (sts, output)

    49 #

    50 def getstatusoutput(cmd):

    51     """Return (status, output) of executing cmd in a shell."""

    52     import os

    53     pipe = os.popen('{ ' + cmd + '; } 2>&1', 'r')

    54     text = pipe.read()

    55     sts = pipe.close()

    56     if sts is None: sts = 0

    57     if text[-1:] == '\n': text = text[:-1]

    58     return sts, text

    59 

    60 

    61 # Make command argument from directory and pathname (prefix space, add quotes).

    62 #

    63 def mk2arg(head, x):

    64     import os

    65     return mkarg(os.path.join(head, x))

    66 

    67 

    68 # Make a shell command argument from a string.

    69 # Return a string beginning with a space followed by a shell-quoted

    70 # version of the argument.

    71 # Two strategies: enclose in single quotes if it contains none;

    72 # otherwise, enclose in double quotes and prefix quotable characters

    73 # with backslash.

    74 #

    75 def mkarg(x):

    76     if '\'' not in x:

    77         return ' \'' + x + '\''

    78     s = ' "'

    79     for c in x:

    80         if c in '\\$"`':

    81             s = s + '\\'

    82         s = s + c

    83     s = s + '"'

    84     return s