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From: jpr@jpradley.jpr.com (Jean-Pierre Radley)
Newsgroups: comp.unix.xenix.sco
Subject: Re: emptying a file and keeping its ownership
Message-ID: <1991Jan01.173014.3236@jpradley.jpr.com>
Date: 1 Jan 91 17:30:14 GMT
References: <1990Dec30.220722.29050@jarvis.csri.toronto.edu> <1990Dec31.214030.7816@athena.mit.edu> <1991Jan1.040621.27634@NCoast.ORG>
Reply-To: jpr@jpradley.UUCP (Jean-Pierre Radley)
Distribution: na
Organization: NYC Public Unix
Lines: 26

In article <1991Jan1.040621.27634@NCoast.ORG> allbery@ncoast.ORG (Brandon S. Allbery KB8JRR) writes:
>As quoted from <1990Dec31.214030.7816@athena.mit.edu> by jik@athena.mit.edu (Jonathan I. Kamens):
>+---------------
>|   Several people have suggested using
>|     > $FILE
>| to truncate a file while retaining its old permissions.  This will work under
>| sh or ksh or bash or other shells that allow null commands for redirection. 
>| Unfortunately, csh and tcsh do not allow such null commands :-(.  Therefore,
>+---------------
>
>	% ls -s file
>	4 file
>	% echo > file
>	% ls -s file
>	0 file
>	% _
>
>Not that I like csh's echo behavior in this case, but it does get around the
>"null command" problem.


I find that in my csh, the following works:
	% : > file
That initial colon does the trick. What mechanism is operating here?

 Jean-Pierre Radley	    NYC Public Unix	jpr@jpr.com	CIS: 72160,1341