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From: "Александр Волков" <a.volkov@rusbitech.ru>
To: Arun Raghavan <arun@accosted.net>
Cc: "alsa-devel@alsa-project.org" <alsa-devel@alsa-project.org>,
	patch@alsa-project.org
Subject: Re: [PATCH - alsa-utils 1/1] arecord: Remove only regular files
Date: Tue, 22 Sep 2015 17:07:21 +0300	[thread overview]
Message-ID: <56016099.30606@rusbitech.ru> (raw)
In-Reply-To: <CACuU-+gX-QnsE_KHwX_55zCZRcKw=V=JvQkuKwvkfNoCDTmL5g@mail.gmail.com>

22.09.2015 16:24, Arun Raghavan пишет:
> On 21 September 2015 at 18:35, Alexander Volkov <a.volkov@rusbitech.ru> wrote:
>> arecord removes a file before writing into it. It's not
>> appropriate in some cases. For example, if you a pass
>> a symlink to a file, then the symlink will be removed
>> while the user expects to record into the symlink's target.
>> Another case is recording into the device file. Some
>> modems provide a tty device file as a voice device.
>> And it's not possible to write into it under root with
>> arecord, because it removes the device file.
>>
>> So check the type of a file before writing into it and
>> remove only regular files.
>>
>> Signed-off-by: Alexander Volkov <a.volkov@rusbitech.ru>
>>
>> diff --git a/aplay/aplay.c b/aplay/aplay.c
>> index 459f7dd..1b2cdfc 100644
>> --- a/aplay/aplay.c
>> +++ b/aplay/aplay.c
>> @@ -2929,6 +2929,7 @@ static void capture(char *orig_name)
>>          char *name = orig_name; /* current filename */
>>          char namebuf[PATH_MAX+1];
>>          off64_t count, rest;            /* number of bytes to capture */
>> +       struct stat statbuf;
>>
>>          /* get number of bytes to capture */
>>          count = calc_count();
>> @@ -2973,7 +2974,10 @@ static void capture(char *orig_name)
>>                          }
>>
>>                          /* open a new file */
>> -                       remove(name);
>> +                       if (!lstat(name, &statbuf)) {
>> +                               if (S_ISREG(statbuf.st_mode))
>> +                                       remove(name);
>> +                       }
>>                          fd = safe_open(name);
>>                          if (fd < 0) {
>>                                  perror(name);
> Would it work to just open with O_TRUNC?
>
> -- Arun
I guess that "remove" is used here to exclude mutual access to the file.
We can record to the created file while some program may read the 
removed file.
Using O_TRUNC will break this use case.

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  reply	other threads:[~2015-09-22 14:10 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-09-21 13:05 [PATCH - alsa-utils 1/1] arecord: Remove only regular files Alexander Volkov
2015-09-22 13:24 ` Arun Raghavan
2015-09-22 14:07   ` Александр Волков [this message]
2015-09-23 13:28     ` Takashi Iwai

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