lib/gen_misc.py

#!/usr/bin/env python

r"""
This module provides many valuable functions such as my_parm_file.
"""

# sys and os are needed to get the program dir path and program name.
import sys
import errno
import os
import ConfigParser
import StringIO
import re
import socket
import tempfile
try:
    import psutil
    psutil_imported = True
except ImportError:
    psutil_imported = False

import gen_print as gp
import gen_cmd as gc

robot_env = gp.robot_env
if robot_env:
    from robot.libraries.BuiltIn import BuiltIn


def add_trailing_slash(dir_path):
    r"""
    Add a trailing slash to the directory path if it doesn't already have one
    and return it.

    Description of arguments:
    dir_path                        A directory path.
    """

    return os.path.normpath(dir_path) + os.path.sep


def which(file_path):
    r"""
    Find the full path of an executable file and return it.

    The PATH environment variable dictates the results of this function.

    Description of arguments:
    file_path                       The relative file path (e.g. "my_file" or
                                    "lib/my_file").
    """

    shell_rc, out_buf = gc.cmd_fnc_u("which " + file_path, quiet=1,
                                     print_output=0, show_err=0)
    if shell_rc != 0:
        error_message = "Failed to find complete path for file \"" +\
                        file_path + "\".\n"
        error_message += gp.sprint_var(shell_rc, 1)
        error_message += out_buf
        if robot_env:
            BuiltIn().fail(gp.sprint_error(error_message))
        else:
            gp.print_error_report(error_message)
            return False

    file_path = out_buf.rstrip("\n")

    return file_path


def dft(value, default):
    r"""
    Return default if value is None.  Otherwise, return value.

    This is really just shorthand as shown below.

    dft(value, default)

    vs

    default if value is None else value

    Description of arguments:
    value                           The value to be returned.
    default                         The default value to return if value is
                                    None.
    """

    return default if value is None else value


def get_mod_global(var_name,
                   default=None,
                   mod_name="__main__"):
    r"""
    Get module global variable value and return it.

    If we are running in a robot environment, the behavior will default to
    calling get_variable_value.

    Description of arguments:
    var_name                        The name of the variable whose value is
                                    sought.
    default                         The value to return if the global does not
                                    exist.
    mod_name                        The name of the module containing the
                                    global variable.
    """

    if robot_env:
        return BuiltIn().get_variable_value("${" + var_name + "}", default)

    try:
        module = sys.modules[mod_name]
    except KeyError:
        gp.print_error_report("Programmer error - The mod_name passed to"
                              + " this function is invalid:\n"
                              + gp.sprint_var(mod_name))
        raise ValueError('Programmer error.')

    if default is None:
        return getattr(module, var_name)
    else:
        return getattr(module, var_name, default)


def global_default(var_value,
                   default=0):
    r"""
    If var_value is not None, return it.  Otherwise, return the global
    variable of the same name, if it exists.  If not, return default.

    This is meant for use by functions needing help assigning dynamic default
    values to their parms.  Example:

    def func1(parm1=None):

        parm1 = global_default(parm1, 0)

    Description of arguments:
    var_value                       The value being evaluated.
    default                         The value to be returned if var_value is
                                    None AND the global variable of the same
                                    name does not exist.
    """

    var_name = gp.get_arg_name(0, 1, stack_frame_ix=2)

    return dft(var_value, get_mod_global(var_name, 0))


def set_mod_global(var_value,
                   mod_name="__main__",
                   var_name=None):
    r"""
    Set a global variable for a given module.

    Description of arguments:
    var_value                       The value to set in the variable.
    mod_name                        The name of the module whose variable is
                                    to be set.
    var_name                        The name of the variable to set.  This
                                    defaults to the name of the variable used
                                    for var_value when calling this function.
    """

    try:
        module = sys.modules[mod_name]
    except KeyError:
        gp.print_error_report("Programmer error - The mod_name passed to"
                              + " this function is invalid:\n"
                              + gp.sprint_var(mod_name))
        raise ValueError('Programmer error.')

    if var_name is None:
        var_name = gp.get_arg_name(None, 1, 2)

    setattr(module, var_name, var_value)


def my_parm_file(prop_file_path):
    r"""
    Read a properties file, put the keys/values into a dictionary and return
    the dictionary.

    The properties file must have the following format:
    var_name<= or :>var_value
    Comment lines (those beginning with a "#") and blank lines are allowed and
    will be ignored.  Leading and trailing single or double quotes will be
    stripped from the value.  E.g.
    var1="This one"
    Quotes are stripped so the resulting value for var1 is:
    This one

    Description of arguments:
    prop_file_path                  The caller should pass the path to the
                                    properties file.
    """

    # ConfigParser expects at least one section header in the file (or you
    # get ConfigParser.MissingSectionHeaderError).  Properties files don't
    # need those so I'll write a dummy section header.

    string_file = StringIO.StringIO()
    # Write the dummy section header to the string file.
    string_file.write('[dummysection]\n')
    # Write the entire contents of the properties file to the string file.
    string_file.write(open(prop_file_path).read())
    # Rewind the string file.
    string_file.seek(0, os.SEEK_SET)

    # Create the ConfigParser object.
    config_parser = ConfigParser.ConfigParser()
    # Make the property names case-sensitive.
    config_parser.optionxform = str
    # Read the properties from the string file.
    config_parser.readfp(string_file)
    # Return the properties as a dictionary.
    return dict(config_parser.items('dummysection'))


def file_to_list(file_path,
                 newlines=0,
                 comments=1,
                 trim=0):
    r"""
    Return the contents of a file as a list.  Each element of the resulting
    list is one line from the file.

    Description of arguments:
    file_path                       The path to the file (relative or
                                    absolute).
    newlines                        Include newlines from the file in the
                                    results.
    comments                        Include comment lines and blank lines in
                                    the results.  Comment lines are any that
                                    begin with 0 or more spaces followed by
                                    the pound sign ("#").
    trim                            Trim white space from the beginning and
                                    end of each line.
    """

    lines = []
    file = open(file_path)
    for line in file:
        if not comments:
            if re.match(r"[ ]*#|^$", line):
                continue
        if not newlines:
            line = line.rstrip("\n")
        if trim:
            line = line.strip()
        lines.append(line)

    return lines


def return_path_list():
    r"""
    This function will split the PATH environment variable into a PATH_LIST
    and return it.  Each element in the list will be normalized and have a
    trailing slash added.
    """

    PATH_LIST = os.environ['PATH'].split(":")
    PATH_LIST = [os.path.normpath(path) + os.sep for path in PATH_LIST]

    return PATH_LIST


def escape_bash_quotes(buffer):
    r"""
    Escape quotes in string and return it.

    The escape style implemented will be for use on the bash command line.

    Example:
    That's all.

    Result:
    That'\''s all.

    The result may then be single quoted on a bash command.  Example:

    echo 'That'\''s all.'

    Description of argument(s):
    buffer                          The string whose quotes are to be escaped.
    """

    return re.sub("\'", "\'\\\'\'", buffer)


def quote_bash_parm(parm):
    r"""
    Return the bash command line parm with single quotes if they are needed.

    Description of arguments:
    parm                            The string to be quoted.
    """

    # If any of these characters are found in the parm string, then the
    # string should be quoted.  This list is by no means complete and should
    # be expanded as needed by the developer of this function.
    bash_special_chars = set(' $')

    if any((char in bash_special_chars) for char in parm):
        return "'" + parm + "'"

    return parm


def get_host_name_ip(host,
                     short_name=0):
    r"""
    Get the host name and the IP address for the given host and return them as
    a tuple.

    Description of argument(s):
    host                            The host name or IP address to be obtained.
    short_name                      Include the short host name in the
                                    returned tuple, i.e. return host, ip and
                                    short_host.
    """

    host_name = socket.getfqdn(host)
    try:
        host_ip = socket.gethostbyname(host)
    except socket.gaierror as my_gaierror:
        message = "Unable to obtain the host name for the following host:" +\
                  "\n" + gp.sprint_var(host)
        gp.print_error_report(message)
        raise my_gaierror

    if short_name:
        host_short_name = host_name.split(".")[0]
        return host_name, host_ip, host_short_name
    else:
        return host_name, host_ip


def pid_active(pid):
    r"""
    Return true if pid represents an active pid and false otherwise.

    Description of argument(s):
    pid                             The pid whose status is being sought.
    """

    try:
        os.kill(int(pid), 0)
    except OSError as err:
        if err.errno == errno.ESRCH:
            # ESRCH == No such process
            return False
        elif err.errno == errno.EPERM:
            # EPERM clearly means there's a process to deny access to
            return True
        else:
            # According to "man 2 kill" possible error values are
            # (EINVAL, EPERM, ESRCH)
            raise

    return True


def to_signed(number,
              bit_width=gp.bit_length(long(sys.maxsize)) + 1):
    r"""
    Convert number to a signed number and return the result.

    Examples:

    With the following code:

    var1 = 0xfffffffffffffff1
    print_var(var1)
    print_var(var1, 1)
    var1 = to_signed(var1)
    print_var(var1)
    print_var(var1, 1)

    The following is written to stdout:
    var1:  18446744073709551601
    var1:  0x00000000fffffffffffffff1
    var1:  -15
    var1:  0xfffffffffffffff1

    The same code but with var1 set to 0x000000000000007f produces the
    following:
    var1:  127
    var1:  0x000000000000007f
    var1:  127
    var1:  0x000000000000007f

    Description of argument(s):
    number                          The number to be converted.
    bit_width                       The number of bits that defines a complete
                                    hex value.  Typically, this would be a
                                    multiple of 32.
    """

    if number < 0:
        return number
    neg_bit_mask = 2**(bit_width - 1)
    if number & neg_bit_mask:
        return ((2**bit_width) - number) * -1
    else:
        return number


def get_child_pids(quiet=1):

    r"""
    Get and return a list of pids representing all first-generation processes
    that are the children of the current process.

    Example:

    children = get_child_pids()
    print_var(children)

    Output:
    children:
      children[0]:           9123

    Description of argument(s):
    quiet                           Display output to stdout detailing how
                                    this child pids are obtained.
    """

    if psutil_imported:
        # If "import psutil" worked, find child pids using psutil.
        current_process = psutil.Process()
        return [x.pid for x in current_process.children(recursive=False)]
    else:
        # Otherwise, find child pids using shell commands.
        print_output = not quiet

        ps_cmd_buf = "ps --no-headers --ppid " + str(os.getpid()) +\
            " -o pid,args"
        # Route the output of ps to a temporary file for later grepping.
        # Avoid using " | grep" in the ps command string because it creates
        # yet another process which is of no interest to the caller.
        temp = tempfile.NamedTemporaryFile()
        temp_file_path = temp.name
        gc.shell_cmd(ps_cmd_buf + " > " + temp_file_path,
                     print_output=print_output)
        # Sample contents of the temporary file:
        # 30703 sleep 2
        # 30795 /bin/bash -c ps --no-headers --ppid 30672 -o pid,args >
        # /tmp/tmpqqorWY
        # Use egrep to exclude the "ps" process itself from the results
        # collected with the prior shell_cmd invocation.  Only the other
        # children are of interest to the caller.  Use cut on the grep results
        # to obtain only the pid column.
        rc, output = \
            gc.shell_cmd("egrep -v '" + re.escape(ps_cmd_buf) + "' "
                         + temp_file_path + " | cut -c1-5",
                         print_output=print_output)
        # Split the output buffer by line into a list.  Strip each element of
        # extra spaces and convert each element to an integer.
        return map(int, map(str.strip, filter(None, output.split("\n"))))