Linux：管道进入Python(ncurses)脚本,stdin和termios

显然这几乎是“ Bad pipe filedescriptor when reading from stdin in python – Stack Overflow”的重复;但是,我认为这种情况稍微复杂一些(并且它不是Windows特定的,因为该线程的结论是).

我目前正在尝试用Python编写一个简单的脚本：我想为脚本提供输入 – 通过命令行参数;或者通过“管道”字符串到此脚本 – 并让脚本使用curses终端接口显示此输入字符串.

完整的脚本,这里称为testcurses.py,如下所示.问题是每当我尝试实际的管道时,这似乎搞乱了stdin,而curses窗口从未显示过.这是一个终端输出：

## CASE 1: THROUGH COMMAND LINE ARGUMENT (arg being stdin):
##
$./testcurses.py -
['-'] 1
stdout/stdin (obj): <open file '<stdout>',mode 'w' at 0xb77dc078> <open file '<stdin>',mode 'r' at 0xb77dc020>
stdout/stdin (fn): 1 0
env(TERM): xterm xterm
stdin_termios_attr [27906,5,1215,35387,15,['x03',... 'x00']]
stdout_termios_attr [27906,... 'x00']]
opening -
obj <open file '<stdin>',mode 'r' at 0xb77dc020>
TYPING blabla HERE
wr TYPING blabla HERE

at end
before curses TYPING blabla HERE
#
# AT THIS POINT:
# in this case,curses window is shown,with the text 'TYPING blabla HERE'
# ################


## CASE 2: THROUGH PIPE
##
## NOTE I get the same output,even if I try syntax as in SO1057638,like:
## python -c "print 'TYPING blabla HERE'" | python testcurses.py -
##
$echo "TYPING blabla HERE" | ./testcurses.py -
['-'] 1
stdout/stdin (obj): <open file '<stdout>',mode 'w' at 0xb774a078> <open file '<stdin>',mode 'r' at 0xb774a020>
stdout/stdin (fn): 1 0
env(TERM): xterm xterm
stdin_termios_attr <class 'termios.error'>::(22,'Invalid argument')
stdout_termios_attr [27906,'x1c','x7f','x15','x04','x00','x01','xff','x11','x13','x1a','x12','x0f','x17','x16','x00']]
opening -
obj <open file '<stdin>',mode 'r' at 0xb774a020>
wr TYPING blabla HERE

at end
before curses TYPING blabla HERE
#
# AT THIS POINT:
# script simply exits,nothing is shown 
# ################

据我所知,问题是： – 每当我们将字符串传递给Python脚本时,Python脚本就会失去对终端的引用作为stdin,并注意到被替换的stdin不再是termios结构 – 并且因为stdin是不再是终端,curses.initscr()立即退出而不渲染任何东西.

所以,我的问题是 – 简而言之：我可以以某种方式实现,语法echo“blabla”| ./testcurses.py – 最终在curses中显示管道字符串？更具体地说：是否可以从Python脚本中检索对调用终端的stdin的引用,即使此脚本被“管道”到？

提前感谢任何指针,

干杯!

PS：testcurses.py脚本：

#!/usr/bin/env python 
# http://www.tuxradar.com/content/code-project-build-ncurses-ui-python
# http://diveintopython.net/scripts_and_streams/stdin_stdout_stderr.html
# http://bytes.com/topic/python/answers/42283-curses-disable-readline-replace-stdin
#
# NOTE: press 'q' to exit curses - Ctrl-C will screw up yer terminal

# ./testcurses.py "blabla"                  # works fine (curseswin shows)
# ./testcurses.py -                     # works fine,(type,enter,curseswins shows):
# echo "blabla" | ./testcurses.py "sdsd"        # fails to raise curses window 
# 
# NOTE: when without pipe: termios.tcgetattr(sys.__stdin__.fileno()): [27906,# NOTE: when with pipe |   : termios.tcgetattr(sys.__stdin__.fileno()): termios.error: (22,'Invalid argument') 

import curses
import sys
import os
import atexit
import termios

def openAnything(source):            
    """URI,filename,or string --> stream

    http://diveintopython.net/xml_processing/index.html#kgp.divein

    This function lets you define parsers that take any input source
    (URL,pathname to local or network file,or actual data as a string)
    and deal with it in a uniform manner.  Returned object is guaranteed
    to have all the basic stdio read methods (read,readline,readlines).
    Just .close() the object when you're done with it.
    """
    if hasattr(source,"read"):
        return source

    if source == '-':
        import sys
        return sys.stdin

    # try to open with urllib (if source is http,ftp,or file URL)
    import urllib                         
    try:                                  
        return urllib.urlopen(source)     
    except (IOError,OSError):            
        pass                              

    # try to open with native open function (if source is pathname)
    try:                                  
        return open(source)               
    except (IOError,OSError):            
        pass                              

    # treat source as string
    import StringIO                       
    return StringIO.StringIO(str(source)) 



def main(argv):

    print argv,len(argv)
    print "stdout/stdin (obj):",sys.__stdout__,sys.__stdin__ 
    print "stdout/stdin (fn):",sys.__stdout__.fileno(),sys.__stdin__.fileno()
    print "env(TERM):",os.environ.get('TERM'),os.environ.get("TERM","unknown")

    stdin_term_attr = 0
    stdout_term_attr = 0
    try:
        stdin_term_attr = termios.tcgetattr(sys.__stdin__.fileno())
    except:
        stdin_term_attr = "%s::%s" % (sys.exc_info()[0],sys.exc_info()[1]) 
    try:
        stdout_term_attr = termios.tcgetattr(sys.__stdout__.fileno())
    except:
        stdout_term_attr = `sys.exc_info()[0]` + "::" + `sys.exc_info()[1]` 
    print "stdin_termios_attr",stdin_term_attr
    print "stdout_termios_attr",stdout_term_attr


    fname = ""
    if len(argv):
        fname = argv[0]

    writetxt = "Python curses in action!"
    if fname != "":
        print "opening",fname
        fobj = openAnything(fname)
        print "obj",fobj
        writetxt = fobj.readline(100) # max 100 chars read
        print "wr",writetxt
        fobj.close()
        print "at end"

    sys.stderr.write("before ")
    print "curses",writetxt
    try:
        myscreen = curses.initscr()
        #~ atexit.register(curses.endwin)
    except:
        print "Unexpected error:",sys.exc_info()[0]

    sys.stderr.write("after initscr") # this won't show,even if curseswin runs fine

    myscreen.border(0)
    myscreen.addstr(12,25,writetxt)
    myscreen.refresh()
    myscreen.getch()

    #~ curses.endwin()
    atexit.register(curses.endwin)

    sys.stderr.write("after end") # this won't show,even if curseswin runs fine


# run the main function - with arguments passed to script:
if __name__ == "__main__":
    main(sys.argv[1:])
    sys.stderr.write("after main1") # these won't show either,sys.stderr.write("after main2")     #  (.. even if curseswin runs fine ..)

$(echo "foo" | ./pipe.py) 3<&0

#!/usr/bin/env python

import sys,os
import curses

output = sys.stdin.readline(100)

# We're finished with stdin. Duplicate inherited fd 3,# which contains a duplicate of the parent process' stdin,# into our stdin,at the OS level (assigning os.fdopen(3)
# to sys.stdin or sys.__stdin__ does not work).
os.dup2(3,0)

# Now curses can initialize.
screen = curses.initscr()
screen.border(0)
screen.addstr(12,output)
screen.refresh()
screen.getch()
curses.endwin()

$exec 3<&0  # spawn subshell
$echo "foo" | ./pipe.py  # works
$echo "bar" | ./pipe.py  # still works