From jeff.a.ryan at gmail.com  Fri Feb  4 14:12:41 2011
From: jeff.a.ryan at gmail.com (Jeff Ryan)
Date: Fri, 4 Feb 2011 07:12:41 -0600
Subject: [Rd] Strange behaviour of read and writeBin
In-Reply-To: <4D4BD675.9060206@uni-muenster.de>
References: <4D4BD675.9060206@uni-muenster.de>
Message-ID: <AANLkTi=tVkRvexQC+j5jBoTARWGEdCitwXXM0qcQD3w2@mail.gmail.com>

from ?seek

?seek? returns the current position (before any move), as a
     (numeric) byte offset from the origin, if relevant, or ?0? if not.

Your string is nul terminated (9 bytes long).  That would be the
current offset. If you only read one byte, you'd have to be more than
0 bytes offset.

Jeff

On Fri, Feb 4, 2011 at 4:35 AM, Christian Ruckert
<cruckert at uni-muenster.de> wrote:
> To me it seems like writeBin() writes one char/byte more than expected.
>
>> con <- file("testbin", "wb")
>> writeBin("ttccggaa", con)
>> close(con)
>
>> con <- file("testbin", "rb")
>> readBin(con, what="character")
> [1] "ttccggaa"
>> seek(con, what=NA)
> [1] 9
>> close(con)
>
>> con <- file("testbin", "rb")
>> readBin(con, what="raw", n=20)
> [1] 74 74 63 63 67 67 61 61 00
>> seek(con, what=NA)
> [1] 9
>> close(con)
>
> As the numbering starts with 0 the position should be 8 and not 9 after
> reading. There were two older threads which look very similar to my problem:
>
> http://tolstoy.newcastle.edu.au/R/e2/devel/06/11/1119.html
> http://r.789695.n4.nabble.com/Re-Problem-reading-binaries-created-with-fortran-More-infos-td974396.html
>
> Thanks in advance,
> Christian
>
>
>
>> sessionInfo()
> R version 2.12.0 (2010-10-15)
> Platform: x86_64-pc-linux-gnu (64-bit)
>
> locale:
> [1] C
>
> attached base packages:
> [1] stats ? ? graphics ?grDevices utils ? ? datasets ?methods ? base
>
> other attached packages:
> [1] Biostrings_2.18.2 IRanges_1.8.8
>
> loaded via a namespace (and not attached):
> [1] Biobase_2.10.0
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>



-- 
Jeffrey Ryan
jeffrey.ryan at lemnica.com

www.lemnica.com



[Rd] Strange behaviour of read and writeBin
Jeff Ryan