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"""Execute shell commands via os.popen() and return status, output.
Interface summary:
import commands
outtext = commands.getoutput(cmd)
(exitstatus, outtext) = commands.getstatusoutput(cmd)
outtext = commands.getstatus(file) # returns output of "ls -ld file"
A trailing newline is removed from the output string.
Encapsulates the basic operation:
pipe = os.popen('{ ' + cmd + '; } 2>&1', 'r')
text = pipe.read()
sts = pipe.close()
[Note: it would be nice to add functions to interpret the exit status.]
"""
# Module 'commands'
#
# Various tools for executing commands and looking at their output and status.
#
# NB This only works (and is only relevant) for UNIX.
# Get 'ls -l' status for an object into a string
#
def getstatus(file):
"""Return output of "ls -ld <file>" in a string."""
return getoutput('ls -ld' + mkarg(file))
# Get the output from a shell command into a string.
# The exit status is ignored; a trailing newline is stripped.
# Assume the command will work with '{ ... ; } 2>&1' around it..
#
def getoutput(cmd):
"""Return output (stdout or stderr) of executing cmd in a shell."""
return getstatusoutput(cmd)[1]
# Ditto but preserving the exit status.
# Returns a pair (sts, output)
#
def getstatusoutput(cmd):
"""Return (status, output) of executing cmd in a shell."""
import os
pipe = os.popen('{ ' + cmd + '; } 2>&1', 'r')
text = pipe.read()
sts = pipe.close()
if sts is None: sts = 0
if text[-1:] == '\n': text = text[:-1]
return sts, text
# Make command argument from directory and pathname (prefix space, add quotes).
#
def mk2arg(head, x):
import os
return mkarg(os.path.join(head, x))
# Make a shell command argument from a string.
# Return a string beginning with a space followed by a shell-quoted
# version of the argument.
# Two strategies: enclose in single quotes if it contains none;
# otherwise, enclose in double quotes and prefix quotable characters
# with backslash.
#
def mkarg(x):
if '\'' not in x:
return ' \'' + x + '\''
s = ' "'
for c in x:
if c in '\\$"`':
s = s + '\\'
s = s + c
s = s + '"'
return s
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