Re: [Bug-wget] stderr file descriptor bug in wget

[Tim Rühsen]

Hi Jason,

I can confirm your observation.

We could add some (likely non-portable) code to find out what you did
and work-around it, e.g. opening /dev/null for stderr.

But please use -q instead of 2>&-. If that is not what you want, please
describe in details what your aim is.

Regards, Tim


On 9/12/19 3:52 AM, Jason Tyler wrote:
> Tested all the way up to wget-1.20.3:
> 
> I noticed that I was getting different results from these two commands:
> 
> wget -O- www.server.com.au/index.html 2>/dev/null
> 
> wget -O- www.server.com.au/index.html 2>&-
> 
> This turned out to be because, when file descriptor 2 has been closed, wget
> opens a socket to the webserver which becomes file descriptor 2 since
> that's the first unused FD.
> 
> wget then sends both its HTTP traffic _and_ the stuff it would normally
> send to standard error to this network socket. (Which is why adding
> "--quiet" corrects the behaviour for the second command above.)
> 
> Looks like the code is somehow doing a write(2,...) regardless of whether
> this is really standard error.
> 
> Sample tcpdump output, showing that "HTTP request sent, awaiting response"
> gets written to the webserver:
> 
> 
> 11:41:59.797549 IP (tos 0x0, ttl 64, id 29147, offset 0, flags [DF], proto
> TCP (6), length 251)
>   jpt.domain.com.au.36822 > 27.96.202.231.http: Flags [P.], cksum 0x04d5
> (incorrect -> 0xa914), seq 12:211, ack 1, win 502, options [nop,nop,TS val
> 1550480171 ecr 3856601808], length 199: HTTP, length: 199
>         GET /index.html HTTP/1.1
>         User-Agent: Wget/1.20.1 (linux-gnu)
>         Accept: */*
>         Accept-Encoding: identity
>         Host: www.pulsemining.com.au
>         Connection: Keep-Alive
> 
> *        HTTP request sent, awaiting response... [!http]   <<<<<< HERE*
> 11:41:59.812221 IP (tos 0x0, ttl 50, id 31586, offset 0, flags [DF], proto
> TCP (6), length 52)
> 
> 
> Jason
>

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