* Freeze opening /dev/stdout
@ 2018-07-20 16:08 João Eiras
2018-07-21 7:04 ` Takashi Yano
0 siblings, 1 reply; 5+ messages in thread
From: João Eiras @ 2018-07-20 16:08 UTC (permalink / raw)
To: cygwin
Hi.
On linux now and then I call a program passing "/dev/stdout" as output
file parameter, so the data is output in the terminal.
For instance, something tiny in C.
#include <fcntl.h>
#include <stdio.h>
int main () {
int fd = open("/dev/stdout", O_WRONLY);
printf("Opened stdout: %d\n", fd);
return 0;
}
Unfortunately, this freezes. The problem (I think) is because
/dev/stdout is a pipe, so the open() call waits forever until a
reader() opens /dev/stdout, which in this case should be the terminal.
Interestingly, this does not affect /dev/stderr which is a link to the
console device.
$ ls -la /dev/std*
lrwxrwxrwx 1 user None 15 Sep 6 2017 /dev/stderr -> /proc/self/fd/2
prw------- 1 user None 0 Jun 4 15:54 /dev/stdin
prw------- 1 user None 0 Jun 4 15:54 /dev/stdout
I've just sent another thread about "/dev/stdin" always being a pipe,
so I guess that is related.
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* Re: Freeze opening /dev/stdout
2018-07-20 16:08 Freeze opening /dev/stdout João Eiras
@ 2018-07-21 7:04 ` Takashi Yano
2018-07-21 11:30 ` Marco Atzeri
2018-07-21 14:56 ` Takashi Yano
0 siblings, 2 replies; 5+ messages in thread
From: Takashi Yano @ 2018-07-21 7:04 UTC (permalink / raw)
To: cygwin
On Fri, 20 Jul 2018 15:35:21 +0200
João Eiras wrote:
> #include <fcntl.h>
> #include <stdio.h>
> int main () {
> int fd = open("/dev/stdout", O_WRONLY);
> printf("Opened stdout: %d\n", fd);
> return 0;
> }
>
> Unfortunately, this freezes. The problem (I think) is because
> /dev/stdout is a pipe, so the open() call waits forever until a
> reader() opens /dev/stdout, which in this case should be the terminal.
I can't reporduce your problem.
The test case outputs:
Opened stdout: 3
$ ls -la /dev/std*
lrwxrwxrwx 1 yano ãªã 15 Mar 26 2016 /dev/stderr -> /proc/self/fd/2
lrwxrwxrwx 1 yano ãªã 15 Mar 26 2016 /dev/stdin -> /proc/self/fd/0
lrwxrwxrwx 1 yano ãªã 15 Mar 26 2016 /dev/stdout -> /proc/self/fd/1
What happens if you execute:
rm /dev/stdin /dev/stdout
ln -s /proc/self/fd/0 /dev/stdin
ln -s /proc/self/fd/1 /dev/output
--
Takashi Yano <takashi.yano@nifty.ne.jp>
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* Re: Freeze opening /dev/stdout
2018-07-21 7:04 ` Takashi Yano
@ 2018-07-21 11:30 ` Marco Atzeri
2018-07-21 14:56 ` Takashi Yano
1 sibling, 0 replies; 5+ messages in thread
From: Marco Atzeri @ 2018-07-21 11:30 UTC (permalink / raw)
To: cygwin
Am 21.07.2018 um 03:19 schrieb Takashi Yano:
> On Fri, 20 Jul 2018 15:35:21 +0200
> João Eiras wrote:
>> #include <fcntl.h>
>> #include <stdio.h>
>> int main () {
>> int fd = open("/dev/stdout", O_WRONLY);
>> printf("Opened stdout: %d\n", fd);
>> return 0;
>> }
>>
>> Unfortunately, this freezes. The problem (I think) is because
>> /dev/stdout is a pipe, so the open() call waits forever until a
>> reader() opens /dev/stdout, which in this case should be the terminal.
>
> I can't reporduce your problem.
>
> The test case outputs:
> Opened stdout: 3
>
same here.
$ ./prova.exe
Opened stdout: 3
João, what exacly is your enviroment and terminal ?
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* Re: Freeze opening /dev/stdout
2018-07-21 7:04 ` Takashi Yano
2018-07-21 11:30 ` Marco Atzeri
@ 2018-07-21 14:56 ` Takashi Yano
2018-07-21 19:22 ` João Eiras
1 sibling, 1 reply; 5+ messages in thread
From: Takashi Yano @ 2018-07-21 14:56 UTC (permalink / raw)
To: cygwin
On Sat, 21 Jul 2018 10:19:03 +0900
Takashi Yano wrote:
> What happens if you execute:
> rm /dev/stdin /dev/stdout
> ln -s /proc/self/fd/0 /dev/stdin
> ln -s /proc/self/fd/1 /dev/output
This is typo.
s/output/stdout/
--
Takashi Yano <takashi.yano@nifty.ne.jp>
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* Re: Freeze opening /dev/stdout
2018-07-21 14:56 ` Takashi Yano
@ 2018-07-21 19:22 ` João Eiras
0 siblings, 0 replies; 5+ messages in thread
From: João Eiras @ 2018-07-21 19:22 UTC (permalink / raw)
To: cygwin
Thanks everyone.
Turns out it's some problem with my setup that is affecting stdin and
stdout. I had no idea that could happen.
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end of thread, other threads:[~2018-07-21 14:56 UTC | newest]
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2018-07-20 16:08 Freeze opening /dev/stdout João Eiras
2018-07-21 7:04 ` Takashi Yano
2018-07-21 11:30 ` Marco Atzeri
2018-07-21 14:56 ` Takashi Yano
2018-07-21 19:22 ` João Eiras
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