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From: achurch@achurch.org (Andrew Church)
Newsgroups: gnu.bash.bug
Subject: Re: bash sets O_NONBLOCK on pts
Date: Thu, 03 Oct 2019 02:49:36 +0900
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Xref: csiph.com gnu.bash.bug:15462

>Well, it's not so uncommon, I had it a few times. Reading on internet
>it seems that other users have it but don't notice it.

The fault could be in some other program accessing the terminal.  Bash
does not clear O_NONBLOCK on displaying a prompt, so if a previously
executed program sets O_NONBLOCK on stdin and then exits, that state
will remain until some other program unsets it.  For example:

$ cat >foo.c
#include <fcntl.h>
int main(void) {fcntl(0, F_SETFL, O_NONBLOCK); return 0;}
^D
$ cc foo.c
$ ./a.out
$ cat
cat: -: Resource temporarily unavailable

  --Andrew Church
    http://achurch.org/