From mboxrd@z Thu Jan  1 00:00:00 1970
From: erik quanstrom <quanstro@quanstro.net>
Date: Thu, 14 Jan 2010 21:54:39 -0500
To: 9fans@9fans.net
Message-ID: <2208182b69351f1e4a1457bc5e2661df@brasstown.quanstro.net>
In-Reply-To: <4d90013f1001141721y6d8098cejf16f2abf3476d01c@mail.gmail.com>
References: <4d90013f1001141721y6d8098cejf16f2abf3476d01c@mail.gmail.com>
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Subject: Re: [9fans] Why isn't there a newline character after the first
	line of /dev/wsys/wctl?
Topicbox-Message-UUID: bf13ce62-ead5-11e9-9d60-3106f5b1d025

> Supposed to just print the first line?, instead, it prints:
>
> read: error reading /mnt/wsys/wctl: buffer too small
>
> Several guys from #plan9 in Freenode told me that that was happening
> because of a missing newline.

not correct.  it is happening because rio thinks the read
requests too few bytes.  sys/src/cmd/rio/xfid.c:791,796.
read reads 1 byte at a time.  it's not clear that read(5)
expressly allows rio to error here, but it seems reasonable enough.
read(1) uses realloc to allocate its buffer and would hang
looking for a newline if rio allowed 1 byte reads.  if
/mnt/wsys/wctl produced a stream of output with no
newlines, read would eventually fail like this

; time read</dev/zero
read: malloc error: virtual memory allocation failed
156.51u 757.95s 916.67r 	 read  # status= malloc

> But, is the current behavior correct? Or is it erroneous?

while correct and consistent, a newline might have made life
a tad easier for shell scripts.

- erik