GNU bug report logs - #7463
truncate

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Rupert Bruce <rbruce <at> nearshore.biz>
To: bug-coreutils <at> gnu.org
Subject: truncate
Date: Mon, 22 Nov 2010 09:41:33 -0500

truncate (GNU coreutils) 7.4

Unexpected behavior:

$ ls -l
total 0
$ truncate --size 0 *.log
$ ls
*.log

I would expect "truncate --size 0 *.log" to truncate any files ending 
with ".log"; instead I get a new file called "*.log"

FYI, one of the first changes I make on a new installation is to alias 
truncate in .bashrc:
alias ll='ls -l'
alias la='ls -A'
alias truncate='truncate --size 0'

Message #8 received at 7463 <at> debbugs.gnu.org (full text, mbox):

From: Erik Auerswald <auerswal <at> unix-ag.uni-kl.de>
To: Rupert Bruce <rbruce <at> nearshore.biz>
Cc: 7463 <at> debbugs.gnu.org
Subject: Re: bug#7463: truncate
Date: Mon, 22 Nov 2010 16:21:08 +0100

Hi,

On Mon, Nov 22, 2010 at 09:41:33AM -0500, Rupert Bruce wrote:
> truncate (GNU coreutils) 7.4
>
> Unexpected behavior:
>
> $ ls -l
> total 0
> $ truncate --size 0 *.log
> $ ls
> *.log
>
> I would expect "truncate --size 0 *.log" to truncate any files ending  
> with ".log"; instead I get a new file called "*.log"

That is caused by your shell, see the "nullglob" option (at least for
bash).

Erik
-- 
Trying to understand [the GNU GPL] in terms of the goals and values
of open source is like trying [to] understand a CD drive's retractable
drawer as a cupholder.
                        -- Richard Stallman

Message #13 received at 7463-done <at> debbugs.gnu.org (full text, mbox):

From: Pádraig Brady <P <at> draigBrady.com>
To: Rupert Bruce <rbruce <at> nearshore.biz>
Cc: 7463-done <at> debbugs.gnu.org
Subject: Re: bug#7463: truncate
Date: Mon, 22 Nov 2010 15:32:04 +0000

On 22/11/10 14:41, Rupert Bruce wrote:
> truncate (GNU coreutils) 7.4
> 
> Unexpected behavior:
> 
> $ ls -l
> total 0
> $ truncate --size 0 *.log
> $ ls
> *.log
> 
> I would expect "truncate --size 0 *.log" to truncate any files ending
> with ".log"; instead I get a new file called "*.log"
> 
> FYI, one of the first changes I make on a new installation is to alias
> truncate in .bashrc:
> alias ll='ls -l'
> alias la='ls -A'
> alias truncate='truncate --size 0'

That's a function of your shell.
Search for "nullglob"

cheers,
Pádraig.

Message #16 received at 7463 <at> debbugs.gnu.org (full text, mbox):

From: Eric Blake <eblake <at> redhat.com>
To: Rupert Bruce <rbruce <at> nearshore.biz>
Cc: 7463 <at> debbugs.gnu.org
Subject: Re: bug#7463: truncate
Date: Mon, 22 Nov 2010 08:48:29 -0700

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

On 11/22/2010 07:41 AM, Rupert Bruce wrote:
> truncate (GNU coreutils) 7.4
> 
> Unexpected behavior:
> 
> $ ls -l
> total 0
> $ truncate --size 0 *.log
> $ ls
> *.log

Thanks for the report.  However, this is not a bug, but how the shell
works.  By default, if a shell glob has no matches (in your case, there
are no files ending in .log in the current directory), then the glob is
passed as-is to the child process.  And truncate assumes that when given
a file name that it should create that file.

> 
> I would expect "truncate --size 0 *.log" to truncate any files ending
> with ".log"; instead I get a new file called "*.log"

Then your expectations need to be refined in light of standardized shell
globbing behavior.

Also, since you mentioned you use bash, you can change your shell
defaults.  For example, 'shopt -s failglob' would make your above
command abort because no .log files were present, rather than passing
the unexpanded glob on as a filename.  Likewise, 'shopt -s nullglob'
would make a non-matching glob silently result in no output (use with
caution; things like 'cat *.log' become a much different beast when
nullglob is enabled).

-- 
Eric Blake   eblake <at> redhat.com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org

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Message #19 received at 7463 <at> debbugs.gnu.org (full text, mbox):

From: Steve Ward <planet36 <at> gmail.com>
To: Rupert Bruce <rbruce <at> nearshore.biz>
Cc: 7463 <at> debbugs.gnu.org
Subject: Re: bug#7463: truncate
Date: Mon, 22 Nov 2010 10:32:25 -0500

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

On Mon, Nov 22, 2010 at 09:41, Rupert Bruce <rbruce <at> nearshore.biz> wrote:

> truncate (GNU coreutils) 7.4
>
> Unexpected behavior:
>
> $ ls -l
> total 0
> $ truncate --size 0 *.log
> $ ls
> *.log
>
> I would expect "truncate --size 0 *.log" to truncate any files ending with
> ".log"; instead I get a new file called "*.log"
>
> FYI, one of the first changes I make on a new installation is to alias
> truncate in .bashrc:
> alias ll='ls -l'
> alias la='ls -A'
> alias truncate='truncate --size 0'
>
>
>
>
>

In newer versions of truncate there is a "--no-create" option.



Steve

[Message part 2 (text/html, inline)]

Message #22 received at 7463 <at> debbugs.gnu.org (full text, mbox):

From: Rupert Bruce <rbruce <at> nearshore.biz>
To: 7463 <at> debbugs.gnu.org
Subject: Re: bug#7463: truncate
Date: Mon, 22 Nov 2010 13:41:16 -0500

The '--no-create' option works well - I have modified my alias to
    alias truncate='truncate -cs 0'

The 'glob' options look interesting ( I've noticed that 'touch *.log' 
does the same thing ) but I'll stick to the scope of the problem at hand...

Thanks to all !

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