From: Peter Stephenson <Peter.Stephenson@csr.com>
To: <zsh-users@zsh.org>
Subject: Re: Extracting the 4th word of the first line in a file - is there a more elegant solution?
Date: Fri, 18 May 2012 14:30:25 +0100 [thread overview]
Message-ID: <20120518143025.7d525f91@pwslap01u.europe.root.pri> (raw)
In-Reply-To: <1337347014.26363.140661077285713.26DAE636@webmail.messagingengine.com>
On Fri, 18 May 2012 15:16:54 +0200
Ronald Fischer <ynnor@mm.st> wrote:
> # $1 is the filename
> line=$(head -n 1 $1)
> field=${lin[(w)4]}
It depends a bit how big the file is. If it's small, it's very easy,
and involves no extra processes (the "$(<...)" is optimised to a read):
field=${$(<$1)[4]}
The disadvantage is that reads the entire file into memory first. It's
hard to think of a way that avoids that that doesn't use an auxiliary
process, but apart from that it's still relatively straightforward
within zsh:
field=${$(read -e <$1)[4]}
This reads a single line from the file and echoes it instead of
assigning it to a parameter. You might want "read -qe" if the file
contains backslashes.
You can do it without an auxiliary process, but with a local variable,
which is probably more efficient and the best compromise:
read -A line <$1
field=$line[4]
--
Peter Stephenson <pws@csr.com> Software Engineer
Tel: +44 (0)1223 692070 Cambridge Silicon Radio Limited
Churchill House, Cambridge Business Park, Cowley Road, Cambridge, CB4 0WZ, UK
Member of the CSR plc group of companies. CSR plc registered in England and Wales, registered number 4187346, registered office Churchill House, Cambridge Business Park, Cowley Road, Cambridge, CB4 0WZ, United Kingdom
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next prev parent reply other threads:[~2012-05-18 14:01 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-18 13:16 Ronald Fischer
2012-05-18 13:30 ` Peter Stephenson [this message]
2012-05-21 19:48 ` Bart Schaefer
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