install_utils.py

import sys
import os
import subprocess


# input/output utils
def ask(question, default='yes'):
    """
    Ask a yes/no question via raw_input() and return their answer.

    source: http://stackoverflow.com/questions/3041986/python-command-line-yes-no-input
    "question" is a string that is presented to the user.
    "default" is the presumed answer if the user just hits <Enter>.
    It must be "yes" (the default), "no" or None (meaning
        an answer is required of the user).

    The "answer" return value is True for "yes" or False for "no".
    """

    valid = {
        'yes': True, 'y': True, 'ye': True,
        'no': False, 'n': False}

    if default is None:
        prompt = ' [y/n] '
    elif default == 'yes':
        prompt = ' [Y/n] '
    elif default == 'no':
        prompt = ' [y/N] '
    else:
        raise ValueError('Invalid default answer: "%s"' % default)

    while True:
        sys.stdout.write(question + prompt)
        choice = raw_input().lower().strip()
        if default is not None and choice == '':
            return valid[default]
        elif choice in valid:
            return valid[choice]
        else:
            sys.stdout.write(
                'Please respond with "yes" or "no" '
                '(or "y" or "n").\n')


def get_input(prompt, default=None):
    """
    Get user's input, only checking for non-empty response.
    """
    user_input = ''
    if default is not None:
        prompt = (
            '{prompt} (default: {})').format(default, prompt=prompt)

    while user_input == '':
        user_input = raw_input(prompt + '\n').strip()

        if user_input == '':
            if default is not None:
                user_input = default
            else:
                print 'The value cannot be blank.'

    return user_input


# helper functions converted from one line script utils to python callable
def print_warn(msg):
    call_command('tput setaf 3')  # 3 = yellow
    sys.stdout.write('[ WARNING ]\n')
    call_command('tput sgr0')
    sys.stderr.write(msg + '\n')


def print_failure():
    call_command('tput setaf 1')  # 1 = red
    print_right('[ FAILED ]')
    call_command('tput sgr0')


def print_success():
    call_command('tput setaf 2')  # 2 = green
    print_right('[ OK ]')
    call_command('tput sgr0')


def print_step(msg):
    call_command('tput setaf 6')
    sys.stdout.write(msg + '\n')
    call_command('tput sgr0')


def print_right(msg):
    call_command('tput cuu1')
    call_command('tput cuf $(tput cols)')
    call_command('tput cub %d' % len(msg))
    sys.stdout.write(msg + '\n')


def exit_with_message(msg):
    sys.stderr.write(msg + '\n')
    sys.exit(1)


def exit_with_failrue(msg):
    print_failure()
    exit_with_message(msg)


# utils using subprocess
def call_command(command):
    """
    Process the given command in a bash shell and return the returncode.

    Warning: Make sure the command is sanitized before
    calling this function to prevent any vulnerability.
    """
    res = subprocess.call(
        command, shell=True,
        executable='/bin/bash')
    return res


def command_exists(command):
    """check if hash can find a path for the command

    From install.sh
    """
    res = call_command('hash ' + command + ' >/dev/null 2>&1')
    if res != 0:
        return False
    else:
        return True


def get_command_output(command):
    try:
        res = subprocess.check_output(
            command, shell=True,
            stderr=subprocess.STDOUT,
            executable='/bin/bash')
    except:
        res = None

    return res


# utils using os
def check_path_exists(path, expand=False):
    if(expand):
        path = os.path.expanduser(path)

    return os.path.exists(path)


# Other helpers
def write_file(filename):
    try:
        out = open(filename, 'w')
    except:
        sys.stderr.write('Unable to write %s.\n' % filename)
        out = None
    return out


def get_http_status(url):
    status_cmd = 'curl --head -s ' + url + ' | head -n 1'
    return get_command_output(status_cmd)

if __name__ == '__main__':
    print_warn('This is for testing install_utils.py')
    ask('Begin testing')
    print call_command('ls > /dev/null')
    print command_exists('python')
    print_step('Next step is')
    print_warn('REALLY long text'*10)
    get_input('just checking:', 'default')