On Wed, Jan 04, 2012 at 06:10:11AM -0500, Balint Szigeti wrote:
> I found this
> : > /var/run/utmp
> in /etc/init.d/bootmisc.sh on Debian 6.0.3
> Can you explain what does " : > " mean?
The ":" is an empty command - which has it's output redirected, thus
truncating the file.
It is documented (deep down) in e.g. the bash(1) man page under
BUILTIN COMMANDS (the sh-compatible shells usually have this):
No effect; the command does nothing beyond expanding
arguments and performing any specified redirections. A
zero exit code is returned.
This is *nearly* the same as :
echo > /var/run/utmp
except that the "echo" would emit a newline character - usually OK for
text files, but not for binary files like utmp...
Hope this helps
Karl E. Jorgensen
- From: Balint Szigeti <firstname.lastname@example.org>