GNU bug report logs - #23227
Inconsistent behavior for --file=~/some-file

Previous Next

Full log

Message #7 received at control <at> debbugs.gnu.org (full text, mbox):

From: Eric Blake <eblake <at> redhat.com>
To: Santiago Ruano Rincón <santiagorr <at> riseup.net>,
 23227-done <at> debbugs.gnu.org,
 "contr >> GNU bug control" <control <at> debbugs.gnu.org>
Subject: Re: bug#23227: Inconsistent behavior for --file=~/some-file
Date: Tue, 5 Apr 2016 16:03:48 -0600

[Message part 1 (text/plain, inline)]

tag 23227 notabug
thanks

On 04/05/2016 03:55 PM, Santiago Ruano Rincón wrote:
> Hi,
> 
> grep fails to parse the tilde (~) to represent $HOME, when it is used to
> give a file's path to --file=, but it works with --file

That's not grep's fault, but the shell's.


> % echo "hola" | LANG=C grep --file ~/tmp-pattern
> hola
> % echo "hola" | LANG=C grep --file=${HOME}/tmp-pattern 
> hola

Try this to see that it is the shell:

$ echo testing --file ~/tmp-pattern
testing --file /home/eblake/tmp-pattern
$ echo testing --file=~/tmp-pattern
testing --file=~/tmp-pattern
$ echo testing --file=$HOME/tmp-pattern
testing --file=/home/eblake/tmp-pattern

Tilde expansion in the shell is defined by POSIX to only happen if ~
occurs as the first character of a word (or, in special cases such as
"export foo=~/bar" where a shell builtin is consuming its operands in
assignment context - but this is not one of those special cases).  IN
other words, for ALL other uses where you are passing '--option=value',
tilde expansion does NOT happen in 'value'; and you are correct that
using '--option value' as two separate arguments (for all long options
where the argument is not optional) is the easiest way to get ~ to the
front of the word and thus have tilde expansion again.

Since this behavior is baked into your shell, there's nothing grep can
do about it, so I'm closing this as not a bug.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

[signature.asc (application/pgp-signature, attachment)]

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.