[ python-Bugs-1633941 ] for line in sys.stdin: doesn't notice EOF the first time

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Bugs item #1633941, was opened at 2007-01-12 05:34
Message generated for change (Comment added) made by draghuram
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Category: Python Library
Group: Python 2.5
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Matthias Klose (doko)
Assigned to: Nobody/Anonymous (nobody)
Summary: for line in sys.stdin: doesn't notice EOF the first time 

Initial Comment:
[forwarded from http://bugs.debian.org/315888]

for line in sys.stdin: doesn't notice EOF the first time when reading from tty.

The test program:

    import sys
    for line in sys.stdin:
            print line,
    print "eof"

A sample session:

    liw at esme$ python foo.py
    foo         <--- I pressed Enter and then Ctrl-D
    foo         <--- then this appeared, but not more
    eof         <--- this only came when I pressed Ctrl-D a second time
    liw at esme$

Seems to me that there is some buffering issue where Python needs to
read end-of-file twice to notice it on all levels. Once should be 
enough.



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Comment By: Raghuram Devarakonda (draghuram)
Date: 2007-01-22 11:34

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I am not entirely sure that this is a bug.

$ cat testfile
line1
line2

$ python foo.py < testfile

This command behaves as expected. Only when the input is from tty, the
above described behaviour happens. That could be because of the terminal
settings where characters may be buffered until a newline is entered.



----------------------------------------------------------------------

Comment By: Raghuram Devarakonda (draghuram)
Date: 2007-01-22 11:34

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I am not entirely sure that this is a bug.

$ cat testfile
line1
line2

$ python foo.py < testfile

This command behaves as expected. Only when the input is from tty, the
above described behaviour happens. That could be because of the terminal
settings where characters may be buffered until a newline is entered.



----------------------------------------------------------------------

Comment By: Gabriel Genellina (gagenellina)
Date: 2007-01-13 23:20

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Same thing occurs on Windows. Even worse, if the line does not end with
CR, Ctrl-Z (EOF in Windows, equivalent to Ctrl-D) has to be pressed 3
times:

D:\Temp>python foo.py
foo  <--- I pressed Enter
^Z   <--- I pressed Ctrl-Z and then Enter again
foo  <--- this appeared
^Z   <--- I pressed Ctrl-Z and then Enter again
<EOF>

D:\Temp>python foo.py
foo^Z   <--- I pressed Ctrl-Z and then Enter
^Z      <--- cursor stays here; I pressed Ctrl-Z and then Enter again
^Z      <--- cursor stays here; I pressed Ctrl-Z and then Enter again
foo <EOF>


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https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1633941&group_id=5470