How to zero out a logfiles

donald.ritchey at donald.ritchey at
Thu Apr 1 09:36:57 EST 2004

Another way to do this, that preserves the concepts of the original 
request is:

	sudo sh -c "echo > /var/log/admfile"

The reason that the original method fails is that the redirection is
done in the original user's shell, and he/she does not have permission
to open the log file as the non-root user ID.

The command listed above works because the redirection of standard out
occurs in the context of a root-owned shell.  This is important because
many times you will want to run a command as another user and need to
send the output to a file that you personally don't have permission to
open.  The general method to handle that is"

sudo sh -c "command_to_run 1 or more parameters >log_file 2>error_file"

Hope this clarifies the situation.

Best wishes.

Donald L. (Don) Ritchey
E-mail:  Donald.Ritchey at

-----Original Message-----
From: Stephen Carville [mailto:stephen at]
Sent: Wednesday, March 31, 2004 7:53 PM
To: Sudo Users
Subject: Re: How to zero out a logfiles

On Wednesday March 31 2004 01:16 pm, Jim Horwath wrote:
> Hi all,
> I have been using sudo for a few months and I'm still
> learning the ropes.  I need to zero a logfile with sudo, but
> I can't get the '>' syntax just right.  I tried to search
> the archives but didn't find any hints.  I can't be the
> first (or last) person who wants to do this.
> For example:
> sudo echo > /var/adm/logfile
> or something similiar

The only way I know how is:

echo | sudo tee /var/log/admfile

Stephen Carville
UNIX and Network Administrator
stephen at
If you have been voting for politicians who promise to give you goodies at 
someone else's expense, then you have no right to complain when they take 
your money and give it to someone else, including themselves.
      --Thomas Sowell (1992)
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