Hi, this is another report related to Cygwin console. Description:
In a noncanonical mode of console (where tty is /dev/consN), if
there is some unprocessed inputs from the user side (i.e., terminal
side), the combination of select(2) (for read) and redirection
causes the next attempt of read(2) to return EOF [i.e., read(0, buf,
sz) = 0] even though the TTY is still alive. Because of this
behavior, the shell session unexpectedly closes because the shell
considers the TTY has been closed.
This only affects the first attempt of read(2) (in each process)
after the redirection.
Repeat-By:
This is a reduced test case to reproduce the problem:
1. Open cygwin console (pseudo console mode) with Bash
This can be done by, for example, opening Run dialog with "Win +
R", typing "C:\cygwin64\bin\bash" and finally pressing "Enter".
2. Run the following command
$ stty -icanon; printf '\e[6n'; read -t 0; : < /dev/null; stty sane
As a result, the terminal response CPR (CSI Pn ; Pn R) to DSR(6)
request (CSI 6 n) is expected to be inserted in the command line.
It should look like the following:
$ 7;1R
However, in the console, the Bash session is closed by the above
command because Bash receives EOF from the TTY and considers the
TTY session has been closed.
Note: Only the first attempt of read(2) after the redirection
returns EOF. This can be confirmed by the following command where
the Bash session does not close.
$ stty -icanon; printf '\e[6n'; read -t 0; : < /dev/null; read;
stty sane
Note: Also the first read(2) fails for each forked process in the
session:
$ stty -icanon; printf '\e[6n'; read -t 0; : < /dev/null; wc -c;
(read||echo fail;read||echo fail2); read; stty sane
0
fail
success
$
Repeat-By (2):
This demonstrates the problem more explicitly by system calls.
1. Open cygwin console (pseudo console mode)
2. Compile and run the attached program `min1.cpp'.
$ g++ -o min1.exe min1.cpp
$ ./min1
The expected result is something like
$ ./min1
CHR CHR CHR CHR CHR CHR CHR
$
However, in the console, it prints EOF and exit. Also the terminal
response CPR appears to be lost.
$ ./min1
EOF
$
Thank you,
Koichi
min1.cpp
Description: Binary data
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