python-通过subprocess.check_output调用的可执行文件在控制台上打印,但未返回结果
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在Windows计算机上,我试图从Python调用外部可执行文件并收集其输出以进行进一步处理.因为必须在调用可执行文件之前设置本地路径变量,所以我创建了一个批处理脚本,该脚本
>首先调用另一个脚本来设置％PATH％和
>然后使用指定的参数调用可执行文件.
* .bat文件如下所示：
@echo off
call set_path.bat
@echo on
executable.exe %*
像这样的Python代码：
print("before call");
result = subprocess.check_output([batfile, parameters], stderr=subprocess.STDOUT, shell=True);
print("after call");
print("------- ------- ------- printing result ------- ------- ------- ");
print(result);
print("------- ------- ------- /printing result ------- ------- ------- ");
现在,从技术上讲,这可行.可执行文件将使用预期的参数进行调用,运行,完成并产生结果.我知道这一点,因为它们被嘲笑地显示在运行Python脚本的控制台中.
但是,结果字符串仅包含批处理脚本返回的内容,而不包含可执行文件的输出：
before call
hello? yes, this is executable.exe
after call
——- ——- ——- printing result ——- ——- ——-
C:\Users\me\Documents\pythonscript\execute\executable.exe “para1|para2|para3”
——- ——- ——- /printing result ——- ——- ——-
subprocess.check_output命令本身以某种方式将预期的输出打印到控制台,在@echo再次打开后,它返回的内容仅包含批处理文件的输出.
如何访问可执行文件的输出并将其保存到字符串以进行进一步的工作？
还是我必须以某种方式修改批处理文件以捕获并打印输出,以使其最终出现在check_output的结果中？如果是这样,我该怎么做呢？
解决方法:
如果程序直接写入控制台(例如通过打开CONOUT $设备)而不是写入过程标准句柄,则唯一的选择是直接读取控制台屏幕缓冲区.为了简化此过程,请从新的空白屏幕缓冲区开始.通过以下功能创建,调整大小,初始化和激活新的屏幕缓冲区：
> CreateConsoleScreenBuffer
> GetConsoleScreenBufferInfoEx(最低支持的客户端：Windows Vista)
> SetConsoleScreenBufferInfoEx(支持的最低客户端：Windows Vista)
> SetConsoleWindowInfo
> FillConsoleOutputCharacter
> SetConsoleActiveScreenBuffer
确保请求GENERIC_READ |调用CreateConsoleScreenBuffer时进行GENERIC_WRITE访问.您稍后需要读取权限才能读取屏幕内容.
专门针对Python,请使用ctypes调用Windows控制台API中的函数.另外,如果通过msvcrt.open_osfhandle用C文件描述符包装句柄,则可以将其作为subprocess.Popen的stdout或stderr参数传递.
无法通过read,ReadFile甚至ReadConsole直接读取屏幕缓冲区的文件描述符或句柄.如果您有文件描述符,请通过msvcrt.get_osfhandle获取基础句柄.给定屏幕缓冲区句柄,调用ReadConsoleOutputCharacter从屏幕读取.下面的示例代码中的read_screen函数演示了从屏幕缓冲区的开始到光标位置的读取.
为了使用控制台API,需要将过程附加到控制台.为此,我提供了一个简单的allocate_console上下文管理器来临时打开控制台.这在GUI应用程序中很有用,而GUI应用程序通常未连接到控制台.
以下示例在Windows 7和10,Python 2.7和3.5中进行了测试.
ctypes定义
import os
import contextlib
import msvcrt
import ctypes
from ctypes import wintypes
kernel32 = ctypes.WinDLL('kernel32', use_last_error=True)
GENERIC_READ = 0x80000000
GENERIC_WRITE = 0x40000000
FILE_SHARE_READ = 1
FILE_SHARE_WRITE = 2
CONSOLE_TEXTMODE_BUFFER = 1
INVALID_HANDLE_VALUE = wintypes.HANDLE(-1).value
STD_OUTPUT_HANDLE = wintypes.DWORD(-11)
STD_ERROR_HANDLE = wintypes.DWORD(-12)
def _check_zero(result, func, args):
if not result:
raise ctypes.WinError(ctypes.get_last_error())
return args
def _check_invalid(result, func, args):
if result == INVALID_HANDLE_VALUE:
raise ctypes.WinError(ctypes.get_last_error())
return args
if not hasattr(wintypes, 'LPDWORD'): # Python 2
wintypes.LPDWORD = ctypes.POINTER(wintypes.DWORD)
wintypes.PSMALL_RECT = ctypes.POINTER(wintypes.SMALL_RECT)
class COORD(ctypes.Structure):
_fields_ = (('X', wintypes.SHORT),
('Y', wintypes.SHORT))
class CONSOLE_SCREEN_BUFFER_INFOEX(ctypes.Structure):
_fields_ = (('cbSize', wintypes.ULONG),
('dwSize', COORD),
('dwCursorPosition', COORD),
('wAttributes', wintypes.WORD),
('srWindow', wintypes.SMALL_RECT),
('dwMaximumWindowSize', COORD),
('wPopupAttributes', wintypes.WORD),
('bFullscreenSupported', wintypes.BOOL),
('ColorTable', wintypes.DWORD * 16))
def __init__(self, *args, **kwds):
super(CONSOLE_SCREEN_BUFFER_INFOEX, self).__init__(
*args, **kwds)
self.cbSize = ctypes.sizeof(self)
PCONSOLE_SCREEN_BUFFER_INFOEX = ctypes.POINTER(
CONSOLE_SCREEN_BUFFER_INFOEX)
LPSECURITY_ATTRIBUTES = wintypes.LPVOID
kernel32.GetStdHandle.errcheck = _check_invalid
kernel32.GetStdHandle.restype = wintypes.HANDLE
kernel32.GetStdHandle.argtypes = (
wintypes.DWORD,) # _In_ nStdHandle
kernel32.CreateConsoleScreenBuffer.errcheck = _check_invalid
kernel32.CreateConsoleScreenBuffer.restype = wintypes.HANDLE
kernel32.CreateConsoleScreenBuffer.argtypes = (
wintypes.DWORD, # _In_ dwDesiredAccess
wintypes.DWORD, # _In_ dwShareMode
LPSECURITY_ATTRIBUTES, # _In_opt_ lpSecurityAttributes
wintypes.DWORD, # _In_ dwFlags
wintypes.LPVOID) # _Reserved_ lpScreenBufferData
kernel32.GetConsoleScreenBufferInfoEx.errcheck = _check_zero
kernel32.GetConsoleScreenBufferInfoEx.argtypes = (
wintypes.HANDLE, # _In_ hConsoleOutput
PCONSOLE_SCREEN_BUFFER_INFOEX) # _Out_ lpConsoleScreenBufferInfo
kernel32.SetConsoleScreenBufferInfoEx.errcheck = _check_zero
kernel32.SetConsoleScreenBufferInfoEx.argtypes = (
wintypes.HANDLE, # _In_ hConsoleOutput
PCONSOLE_SCREEN_BUFFER_INFOEX) # _In_ lpConsoleScreenBufferInfo
kernel32.SetConsoleWindowInfo.errcheck = _check_zero
kernel32.SetConsoleWindowInfo.argtypes = (
wintypes.HANDLE, # _In_ hConsoleOutput
wintypes.BOOL, # _In_ bAbsolute
wintypes.PSMALL_RECT) # _In_ lpConsoleWindow
kernel32.FillConsoleOutputCharacterW.errcheck = _check_zero
kernel32.FillConsoleOutputCharacterW.argtypes = (
wintypes.HANDLE, # _In_ hConsoleOutput
wintypes.WCHAR, # _In_ cCharacter
wintypes.DWORD, # _In_ nLength
COORD, # _In_ dwWriteCoord
wintypes.LPDWORD) # _Out_ lpNumberOfCharsWritten
kernel32.ReadConsoleOutputCharacterW.errcheck = _check_zero
kernel32.ReadConsoleOutputCharacterW.argtypes = (
wintypes.HANDLE, # _In_ hConsoleOutput
wintypes.LPWSTR, # _Out_ lpCharacter
wintypes.DWORD, # _In_ nLength
COORD, # _In_ dwReadCoord
wintypes.LPDWORD) # _Out_ lpNumberOfCharsRead
职能
@contextlib.contextmanager
def allocate_console():
allocated = kernel32.AllocConsole()
try:
yield allocated
finally:
if allocated:
kernel32.FreeConsole()
@contextlib.contextmanager
def console_screen(ncols=None, nrows=None):
info = CONSOLE_SCREEN_BUFFER_INFOEX()
new_info = CONSOLE_SCREEN_BUFFER_INFOEX()
nwritten = (wintypes.DWORD * 1)()
hStdOut = kernel32.GetStdHandle(STD_OUTPUT_HANDLE)
kernel32.GetConsoleScreenBufferInfoEx(
hStdOut, ctypes.byref(info))
if ncols is None:
ncols = info.dwSize.X
if nrows is None:
nrows = info.dwSize.Y
elif nrows > 9999:
raise ValueError('nrows must be 9999 or less')
fd_screen = None
hScreen = kernel32.CreateConsoleScreenBuffer(
GENERIC_READ | GENERIC_WRITE,
FILE_SHARE_READ | FILE_SHARE_WRITE,
None, CONSOLE_TEXTMODE_BUFFER, None)
try:
fd_screen = msvcrt.open_osfhandle(
hScreen, os.O_RDWR | os.O_BINARY)
kernel32.GetConsoleScreenBufferInfoEx(
hScreen, ctypes.byref(new_info))
new_info.dwSize = COORD(ncols, nrows)
new_info.srWindow = wintypes.SMALL_RECT(
Left=0, Top=0, Right=(ncols - 1),
Bottom=(info.srWindow.Bottom - info.srWindow.Top))
kernel32.SetConsoleScreenBufferInfoEx(
hScreen, ctypes.byref(new_info))
kernel32.SetConsoleWindowInfo(hScreen, True,
ctypes.byref(new_info.srWindow))
kernel32.FillConsoleOutputCharacterW(
hScreen, u'\0', ncols * nrows, COORD(0,0), nwritten)
kernel32.SetConsoleActiveScreenBuffer(hScreen)
try:
yield fd_screen
finally:
kernel32.SetConsoleScreenBufferInfoEx(
hStdOut, ctypes.byref(info))
kernel32.SetConsoleWindowInfo(hStdOut, True,
ctypes.byref(info.srWindow))
kernel32.SetConsoleActiveScreenBuffer(hStdOut)
finally:
if fd_screen is not None:
os.close(fd_screen)
else:
kernel32.CloseHandle(hScreen)
def read_screen(fd):
hScreen = msvcrt.get_osfhandle(fd)
csbi = CONSOLE_SCREEN_BUFFER_INFOEX()
kernel32.GetConsoleScreenBufferInfoEx(
hScreen, ctypes.byref(csbi))
ncols = csbi.dwSize.X
pos = csbi.dwCursorPosition
length = ncols * pos.Y + pos.X + 1
buf = (ctypes.c_wchar * length)()
n = (wintypes.DWORD * 1)()
kernel32.ReadConsoleOutputCharacterW(
hScreen, buf, length, COORD(0,0), n)
lines = [buf[i:i+ncols].rstrip(u'\0')
for i in range(0, n[0], ncols)]
return u'\n'.join(lines)
例
if __name__ == '__main__':
import io
import textwrap
import subprocess
text = textwrap.dedent('''\
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do
eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut
enim ad minim veniam, quis nostrud exercitation ullamco laboris
nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor
in reprehenderit in voluptate velit esse cillum dolore eu
fugiat nulla pariatur. Excepteur sint occaecat cupidatat non
proident, sunt in culpa qui officia deserunt mollit anim id est
laborum.''')
cmd = ("python -c \""
"print('piped output');"
"conout = open(r'CONOUT$', 'w');"
"conout.write('''%s''')\"" % text)
with allocate_console() as allocated:
with console_screen(nrows=1000) as fd_conout:
stdout = subprocess.check_output(cmd).decode()
conout = read_screen(fd_conout)
with io.open('result.txt', 'w', encoding='utf-8') as f:
f.write(u'stdout:\n' + stdout)
f.write(u'\nconout:\n' + conout)
产量
stdout:
piped output
conout:
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do
eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut
enim ad minim veniam, quis nostrud exercitation ullamco laboris
nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor
in reprehenderit in voluptate velit esse cillum dolore eu
fugiat nulla pariatur. Excepteur sint occaecat cupidatat non
proident, sunt in culpa qui officia deserunt mollit anim id est
laborum.
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