[issue45511] Batch-mode input() limited to 4095 characters on *NIX

[Eryk Sun]

Eryk Sun  added the comment:

> but I'm interrested in knowing more about the issue/original cause.

When the readline module is imported in interactive mode, the 
PyOS_ReadlineFunctionPointer function pointer is set to call_readline(), which 
uses GNU Readline. Otherwise PyOS_Readline() calls PyOS_StdioReadline(), which 
calls my_fgets() and thus C standard I/O fgets().

In Linux, when the terminal is in canonical mode, a low-level read() is 
buffered with a limit of 4096 bytes. If the limit is exceeded, the call returns 
just the first 4095 bytes plus a trailing newline. You can verify this with 
os.read(0, 5000). GNU Readline disables canonical mode and works with the 
terminal at a lower level. I am far from an expert with Unix terminals, but 
here's the basics of something that allows input() to read more than 4096 
characters without having to import the readline module.

import sys
import termios

LFLAG = 3
settings = termios.tcgetattr(sys.stdin.fileno())
settings[LFLAG] &= ~termios.ICANON
termios.tcsetattr(sys.stdin.fileno(), termios.TCSANOW, settings)

try:
s = input()
finally:
settings[LFLAG] |= termios.ICANON
termios.tcsetattr(sys.stdin.fileno(), termios.TCSANOW, settings)

print(len(s))

--
nosy: +eryksun

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue45511] Batch-mode input() limited to 4095 characters on *NIX

[Grégory Starck]

Grégory Starck  added the comment:

> This does not seems to be a copypaste issue.

well. it's either not a prob in my_fgets()/fgets IMO. what the process reads on 
its stdin is already corrupted/broken.

but I'm interrested in knowing more about the issue/original cause.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue45511] Batch-mode input() limited to 4095 characters on *NIX

[Romuald Brunet]

Romuald Brunet  added the comment:

This does not seems to be a copypaste issue.

I've re-tested using xdotool to "manually" type 5000 characters in to a X 
terminal (gnome-terminal and xterm, to be sure) and got the same result.

I also have 4 read(0, "...") with the last one ending with a "\n", that's a 
very strange behavior


I tried to test the same thing on a macOS version, but the input() / terminal 
would not let me insert more than 1024 characters

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue45511] Batch-mode input() limited to 4095 characters on *NIX

[Grégory Starck]

Grégory Starck  added the comment:

reproduced and also seen in my_fgets.

but strange. it's fgets that seems to return/insert a \n after 4096 chars read 
from stdin :O I dont quite get. at all haha.

now just straced that.. we see 4 read of 1024 bytes/chars. 

and with strace -s 1025 I can see the last one : 

read(0, 
"AAA\n",
 1024) = 1024

so it's a prob in copy/paste of OS or something ?

--
nosy: +g.sta...@gmail.com
versions: +Python 3.10, Python 3.8, Python 3.9

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue45511] Batch-mode input() limited to 4095 characters on *NIX

[Terry J. Reedy]

Change by Terry J. Reedy :


--
stage:  -> test needed
title: input() method limited to 4095 characters on *NIX -> Batch-mode input() 
limited to 4095 characters on *NIX
versions: +Python 3.11 -Python 3.10, Python 3.6, Python 3.7, Python 3.8, Python 
3.9

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com