[Python-bugs-list] [ python-Bugs-470634 ] readlines() on linux requires 2 ^D's

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Bugs item #470634, was opened at 2001-10-12 10:06
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Category: Python Interpreter Core
Group: Platform-specific
Status: Open
Resolution: None
Priority: 5
Submitted By: Nobody/Anonymous (nobody)
Assigned to: Nobody/Anonymous (nobody)
Summary: readlines() on linux requires 2 ^D's

Initial Comment:
Platform:

This bug has been confirmed on Python 1.5.2, 2.0.1, and
2.1.1 running on Debian Linux 2.2 w/kernel 2.4.9 and
libc6 2.2.4, as well as Python 1.5.2 running on Debian
Linux 2.0 w/kernel 2.0.38 and libc6 2.0.7.

It has been found *not* to happen with Python 2.1.1 on
Solaris 8 and Cygwin.

Bug Description:
When using the standard idiom:

for line in sys.stdin.readlines():
  print line

...to loop through lines submitted to stdin, and
providing that input interactively (i.e. typing at the
console), it is necessary to press ^D *twice* at the
start of line of input to terminate input.  The
behavior can be noticed both in python's interactive
mode *and* when running a script.  Redirected input
does not show this problem, that is if the above lines
are contained in myscript.py, and you execute:

cat | myscript.py

A single ^D is sufficient to terminate inputs.

Also, the problem is unique to the "readlines()"
method.  If you code the loop as

for line in sys.stdin.read().splitlines():

then a single ^D at the beginning of a line is
sufficient to terminate input.


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>Comment By: Guido van Rossum (gvanrossum)
Date: 2001-10-12 10:16

Message:
Logged In: YES 
user_id=6380

Confirmed on Linux (RH 6.2) with 2.2 from CVS too.

I think it's probably a logic error in readlines() -- maybe
the first EOF ends it reading the current line, but then it
needs another EOF to break out of the loop.


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