Related to: FC4 Sluggishness on a 466 MHz Celeron

[Gordon Messmer]

Mike McCarty wrote:
> 
> # echo 59 > /proc/sys/vm/swappiness
> 
> which is what I took him to mean, as well.
> 
> I don't understand why echo should be able to write a file that
> an editor cannot.

<pedantic mode>

In the above context, "echo" does not edit the file, the shell does.

When you redirect output with the '>' or '>>' operators, the shell opens 
the file to the right of the operator and attaches it to the stdout file 
descriptor before it launches the command to the left of the operator. 
That's why the command:

$ sudo echo 59 > /proc/sys/vm/swappiness

.. doesn't work.  Although "echo" would run as the root user, the shell 
that the hypothetical user is running is not.  Because it's the shell's 
job to open /proc/sys/vm/swappiness before running "sudo", the attempt 
to modify the file will fail.

I just thought I'd toss that in to the conversation.  :)

</pedantic>