From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from firstgate.proxmox.com (firstgate.proxmox.com [212.224.123.68]) by lore.proxmox.com (Postfix) with ESMTPS id 865EE1FF145 for ; Thu, 05 Feb 2026 14:39:51 +0100 (CET) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id 605D811135; Thu, 5 Feb 2026 14:40:24 +0100 (CET) Message-ID: Date: Thu, 5 Feb 2026 14:40:18 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 proxmox-backup 10/16] client: treat minus sign as stdin To: Christian Ebner , pbs-devel@lists.proxmox.com References: <20260130164552.281581-1-r.obkircher@proxmox.com> <20260130164552.281581-11-r.obkircher@proxmox.com> Content-Language: en-US, de-AT From: Robert Obkircher In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Bm-Milter-Handled: 55990f41-d878-4baa-be0a-ee34c49e34d2 X-Bm-Transport-Timestamp: 1770298741427 X-SPAM-LEVEL: Spam detection results: 0 AWL 0.052 Adjusted score from AWL reputation of From: address BAYES_00 -1.9 Bayes spam probability is 0 to 1% DMARC_MISSING 0.1 Missing DMARC policy KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment RCVD_IN_VALIDITY_CERTIFIED_BLOCKED 0.001 ADMINISTRATOR NOTICE: The query to Validity was blocked. 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SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record Message-ID-Hash: GRCQYY3GAQIJ7TO46FJQAGTV3AKNIHAS X-Message-ID-Hash: GRCQYY3GAQIJ7TO46FJQAGTV3AKNIHAS X-MailFrom: r.obkircher@proxmox.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; loop; banned-address; emergency; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header X-Mailman-Version: 3.3.10 Precedence: list List-Id: Proxmox Backup Server development discussion List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On 2/4/26 15:42, Christian Ebner wrote: > On 2/4/26 3:00 PM, Robert Obkircher wrote: >> >> On 2/2/26 13:14, Christian Ebner wrote: >>> On 1/30/26 5:45 PM, Robert Obkircher wrote: >>>> Treat "-" as an alias for "/dev/stdin". If there is an actual file >>>> with that name it can still be read via "./-". >>>> >>>> Signed-off-by: Robert Obkircher >>>> --- >>>>    proxmox-backup-client/src/main.rs | 7 +++++++ >>>>    1 file changed, 7 insertions(+) >>>> >>>> diff --git a/proxmox-backup-client/src/main.rs >>>> b/proxmox-backup-client/src/main.rs >>>> index 7fc711fd..37878b01 100644 >>>> --- a/proxmox-backup-client/src/main.rs >>>> +++ b/proxmox-backup-client/src/main.rs >>>> @@ -845,6 +845,13 @@ async fn create_backup( >>>>            } >>>>            target_set.insert(target.clone()); >>>>    +        // one can still use ./- to refer to an actual file with >>>> that name >>>> +        let filename = if filename == "-" { >>>> +            String::from("/dev/stdin") >>> >>> should we add a warning here? >>> >>> This is actually a breaking change, but guarding it behind a flag is >>> maybe a bit overkill. We could check if the file exists before >>> continuing and if so fail with an appropriate warning/error? >> >> Another option would be to just require /dev/stdin and print a hint >> about that if the user tries to specify "-". What do you think >> about that? > > Might be the better option for the time being, yes. And must be > documented correctly of course. The '-' shortcut could still be > added as breaking change in a future version. > > But now I'm wondering, how is the multi archive case handled if > reading from stdin? > > To extend your example in the cover letter: `ssh host cmd | > proxmox-backup-client backup a.img:/dev/stdin b.img:/dev/stdin` > > Without having tested it I guess this will fail on the second > archive creation since that will be empty?  Yes, this specific example will fail for that reason. But in general, running something like `cat - test.txt -` or `cat /dev/stdin test.txt /dev/stdin` actually works if you run it interactively in a terminal and hit `ctrl+d` to end the first input. > > This should be checked and fail on command invocation instead.  This is not trivial because of symlinks: $ file /dev/stdin /dev/stdin: symbolic link to /proc/self/fd/0 $ file /proc/self/fd/0 /proc/self/fd/0: symbolic link to /dev/pts/5 $ echo | file /proc/self/fd/0 /proc/self/fd/0: symbolic link to pipe:[317534] I can think of two solutions: 1) Since we already read the metadata of all inputs at the start, we could check that the inode number is unique for fifo files. 2) Simply check if /dev/stdin and/or /proc/self/fd/0 appear multiple times as strings. In this case a warning might be better than an error. I also just realized that my patch didn't actually work interactively, because pts devices are not fifo pipes. Somehow I've only ever tested this with my script or non-interactive pipes. I was able to fix this by allowing character devices, but initially I got some really weird behavior. For example, a single ctrl+D was not enough to end the stream and I also got errors about multiple smaller chunks being sent. The problem was that FixedChunkStream continued to call (try_)poll_next even after it got a None, which is not allowed. > > > The only real advantage of "-" is that it could be implemented in > a> platform independent way by reading from io::stdin(). That would >> require a lot of changes though. >> >>> >>>> +        } else { >>>> +            filename >>>> +        }; >>>> + >>>>            use std::os::unix::fs::FileTypeExt; >>>>              let metadata = std::fs::metadata(&filename) >>> >