commit 1aff6b875213d70a05d0cb5d86a5ff9914ce6e41 Author: Damian Johnson atagar@torproject.org Date: Sun Oct 9 03:24:44 2011 -0700

General system utilities

Adding some simple utility functions that I'll need later. These are rewrites of their arm counterparts, which I wrote before discovering the subprocess module. --- stem/util/__init__.py | 2 +- stem/util/system.py | 109 +++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 110 insertions(+), 1 deletions(-)

diff --git a/stem/util/__init__.py b/stem/util/__init__.py index e079d62..b778b6f 100644 --- a/stem/util/__init__.py +++ b/stem/util/__init__.py @@ -2,5 +2,5 @@ Utility functions used by the stem library. """

-__all__ = ["enum", "term"] +__all__ = ["enum", "system", "term"]

diff --git a/stem/util/system.py b/stem/util/system.py new file mode 100644 index 0000000..3c520e8 --- /dev/null +++ b/stem/util/system.py @@ -0,0 +1,109 @@ +""" +Helper functions for working with the underlying system. These are mostly os +dependent, only working on linux, osx, and bsd. +""" + +import os +import time +import subprocess + +from stem.util import log + +# Mapping of commands to if they're available or not. This isn't always +# reliable, failing for some special commands. For these the cache is +# prepopulated to skip lookups. +CMD_AVAILABLE_CACHE = {"ulimit": True} + +def is_available(command, cached=True): + """ + Checks the current PATH to see if a command is available or not. If more + than one command is present (for instance "ls -a | grep foo") then this + just checks the first. + + Arguments: + command (str) - command to search for + cached (bool) - makes use of available cached results if True + + Returns: + True if an executable we can use by that name exists in the PATH, False + otherwise + """ + + if " " in command: command = command.split(" ")[0] + + if cached and command in CMD_AVAILABLE_CACHE: + return CMD_AVAILABLE_CACHE[command] + else: + cmd_exists = False + for path in os.environ["PATH"].split(os.pathsep): + cmd_path = os.path.join(path, command) + + if os.path.exists(cmd_path) and os.access(cmd_path, os.X_OK): + cmd_exists = True + break + + CMD_AVAILABLE_CACHE[command] = cmd_exists + return cmd_exists + +def is_running(command, suppress_exc = True): + """ + Checks for if a process with a given name is running or not. + + Arguments: + command (str) - process name to be checked + suppress_exc (bool) - if True then None is returned on failure, otherwise + this raises the exception + + Returns: + True if the process is running, False otherwise + + Raises: + OSError if this can't be determined and suppress_exc is False + """ + + command_listing = call("ps -A co command") + + if command_listing: + return command in command_listing + else: + if suppress_exc: return None + else: raise OSError("Unable to check via 'ps -A co command'") + +def call(command, suppress_exc = True): + """ + Issues a command in a subprocess, blocking until completion and returning the + results. This is not actually ran in a shell so pipes and other shell syntax + aren't permitted. + + Arguments: + command (str) - command to be issued + suppress_exc (bool) - if True then None is returned on failure, otherwise + this raises the exception + + Returns: + List with the lines of output from the command, None in case of failure if + suppress_exc is True + + Raises: + OSError if this fails and suppress_exc is False + """ + + try: + start_time = time.time() + stdout, stderr = subprocess.Popen(command.split(), stdout = subprocess.PIPE, stderr = subprocess.PIPE).communicate() + stdout, stderr = stdout.strip(), stderr.strip() + runtime = time.time() - start_time + + msg = "system call: %s (runtime: %0.2f)" % (command, runtime) + if stderr: msg += "\nstderr: %s" % stderr + log.log(log.DEBUG, msg) + + if stdout: return stdout.split("\n") + else: return [] + except OSError, exc: + msg = "system call (failed): %s (error: %s)" % (command, exc) + log.log(log.INFO, msg) + + if suppress_exc: return None + else: raise exc +