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# Copyright
"""
Automatic pager for terminal output (a la Git).
"""
import sys, os, select
# see http://nex-3.com/posts/73-git-style-automatic-paging-in-ruby
def run_pager(paginate=None):
"""
paginate should be one of 'never', 'auto', or 'always'.
usage: just call this function and continue using sys.stdout like
you normally would.
"""
if paginate == 'never' \
or sys.platform == 'win32' \
or not hasattr(sys.stdout, 'isatty') \
or sys.stdout.isatty() == False:
return
if paginate == 'auto':
if 'LESS' not in os.environ:
os.environ['LESS'] = '' # += doesn't work on undefined var
# don't page if the input is short enough
os.environ['LESS'] += ' -FRX'
if 'PAGER' in os.environ:
pager = os.environ['PAGER']
else:
pager = 'less'
read_fd, write_fd = os.pipe()
if os.fork() == 0:
# child process
os.close(read_fd)
os.close(0)
os.dup2(write_fd, 1)
os.close(write_fd)
if hasattr(sys.stderr, 'isatty') and sys.stderr.isatty() == True:
os.dup2(1, 2)
return
# parent process, become pager
os.close(write_fd)
os.dup2(read_fd, 0)
os.close(read_fd)
# Wait until we have input before we start the pager
select.select([0], [], [])
os.execlp(pager, pager)
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