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# -*- coding: utf-8 -*- #
# Copyright 2013 Google LLC. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""General console printing utilities used by the Cloud SDK."""
import os
import signal
import subprocess
import sys
from fire.console import console_attr
from fire.console import console_pager
from fire.console import encoding
from fire.console import files
def IsInteractive(output=False, error=False, heuristic=False):
"""Determines if the current terminal session is interactive.
sys.stdin must be a terminal input stream.
Args:
output: If True then sys.stdout must also be a terminal output stream.
error: If True then sys.stderr must also be a terminal output stream.
heuristic: If True then we also do some additional heuristics to check if
we are in an interactive context. Checking home path for example.
Returns:
True if the current terminal session is interactive.
"""
if not sys.stdin.isatty():
return False
if output and not sys.stdout.isatty():
return False
if error and not sys.stderr.isatty():
return False
if heuristic:
# Check the home path. Most startup scripts for example are executed by
# users that don't have a home path set. Home is OS dependent though, so
# check everything.
# *NIX OS usually sets the HOME env variable. It is usually '/home/user',
# but can also be '/root'. If it's just '/' we are most likely in an init
# script.
# Windows usually sets HOMEDRIVE and HOMEPATH. If they don't exist we are
# probably being run from a task scheduler context. HOMEPATH can be '\'
# when a user has a network mapped home directory.
# Cygwin has it all! Both Windows and Linux. Checking both is perfect.
home = os.getenv('HOME')
homepath = os.getenv('HOMEPATH')
if not homepath and (not home or home == '/'):
return False
return True
def More(contents, out, prompt=None, check_pager=True):
"""Run a user specified pager or fall back to the internal pager.
Args:
contents: The entire contents of the text lines to page.
out: The output stream.
prompt: The page break prompt.
check_pager: Checks the PAGER env var and uses it if True.
"""
if not IsInteractive(output=True):
out.write(contents)
return
if check_pager:
pager = encoding.GetEncodedValue(os.environ, 'PAGER', None)
if pager == '-':
# Use the fallback Pager.
pager = None
elif not pager:
# Search for a pager that handles ANSI escapes.
for command in ('less', 'pager'):
if files.FindExecutableOnPath(command):
pager = command
break
if pager:
# If the pager is less(1) then instruct it to display raw ANSI escape
# sequences to enable colors and font embellishments.
less_orig = encoding.GetEncodedValue(os.environ, 'LESS', None)
less = '-R' + (less_orig or '')
encoding.SetEncodedValue(os.environ, 'LESS', less)
# Ignore SIGINT while the pager is running.
# We don't want to terminate the parent while the child is still alive.
signal.signal(signal.SIGINT, signal.SIG_IGN)
p = subprocess.Popen(pager, stdin=subprocess.PIPE, shell=True)
enc = console_attr.GetConsoleAttr().GetEncoding()
p.communicate(input=contents.encode(enc))
p.wait()
# Start using default signal handling for SIGINT again.
signal.signal(signal.SIGINT, signal.SIG_DFL)
if less_orig is None:
encoding.SetEncodedValue(os.environ, 'LESS', None)
return
# Fall back to the internal pager.
console_pager.Pager(contents, out, prompt).Run()
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