#############################################################
# split and interactively page a string, file, or stream of
# text to stdout; when run as a script, page stdin or file 
# whose name is passed on cmdline; if input is stdin, can't
# use it for user reply--use platform-specific tools or gui;
#############################################################

import sys, string

def getreply():
    """ 
    read a reply key from an interactive user
    even if stdin redirected to a file or pipe
    """
    if sys.stdin.isatty():                       # if stdin is console
        return raw_input('?')                    # read reply line from stdin 
    else:
        if sys.platform[:3] == 'win':            # if stdin was redirected
            import msvcrt                        # can't use to ask a user 
            msvcrt.putch('?')
            key = msvcrt.getche()                # use windows console tools
            msvcrt.putch('\n')                   # getch() does not echo key
            return key
        elif sys.platform[:5] == 'linux':        # use linux console device 
            print '?',                           # strip eoln at line end
            console = open('/dev/tty')
            line = console.readline()[:-1]
            return line
        else:
            print '[pause]'                      # else just pause--improve me
            import time                          # see also modules curses, tty
            time.sleep(5)                        # or copy to temp file, rerun
            return 'y'                           # or gui popup, tk key bind

def more(text, numlines=10):
    """
    split multi-line string to stdout
    """
    lines = string.split(text, '\n')
    while lines:
        chunk = lines[:numlines]
        lines = lines[numlines:]
        for line in chunk: print line
        if lines and getreply() not in ['y', 'Y']: break 

if __name__ == '__main__':                       # when run, not when imported
    if len(sys.argv) == 1:                       # if no command-line arguments
        more(sys.stdin.read())                   # page stdin, no raw_inputs
    else:
        more(open(sys.argv[1]).read())           # else page filename argument