very urgent Unix question!?.

octane

octane

I have issues, OK!
I've just type 'dc var' instead of 'cd var' and the command went through without an error .. this worries me.

What the hell did I do?

Help!?.
 
well, dc is an arbitrary precision calculator (according to the man pages).

check the man pages. v, a, and r are probably just some options/flags for dc. no harm no foul.
 
Type "man dc" for a brief summary of what dc (or any command) does.

In HP/UX, "dc" is just a command-line calculator program. Alas, I can't get to a Darwin prompt right now.
 
octane said:
What the hell did I do?.
Click to expand...

I just did a: man dc and apparently, it's a Polish calculator of all things.

But I'm still non the wiser as to whether this has successfully shafted my machine or not...
 
Oh no! You might calculate your files! :)

To my knowledge, the only really dangerous command is rm (remove).

And this is my usual advice for dealing with UNIX commands: Always man your commands.
 
That's reverse polish notation, i.e. instead of 1 + 5 (return) it's 1 5 +

Named after a fellow called Polish, I think, not that it's a Polish way of doing math. Engineers seem to swear by it, though I'm not quite clear on what they see in it.

Arden - the dangerous commands are many and varied... rm is however the one you're most likely to accidentally misuse.
 
Okay, the most dangerous command is rm, and it's the most common dangerous command. Anywho...

I think reverse notation is something like 1 = 5 +, and when you hit return it gives you 6. I used a calculator like that once... it's a bit confusing at first.
 
Named after a fellow called Polish, I think, not that it's a Polish way of doing math.
Click to expand...
AFAIK it is a Polish way of doing math, developed (IIRC) by the Lvov/Warsaw school of mathematicians and logicians. Simply put, IIRC, it amounts to some kind of functional notation: 5+6 would be written as (5,6)+ In logic one often finds reverse Polish notation, which would be +(5,6). The notation we all know (5+6) is called infix, because the operator (+) is put in between. Reverse Polish notation is prefix and Polish notation postfix.
This all comes from the vast gray area inside my skull labelled long term unsorted miscellanea and may not be 100% accurate ... :)

Google is your friend: I found this.
 
Cat said:
AFAIK it is a Polish way of doing math, developed (IIRC) by the Lvov/Warsaw school of mathematicians and logicians. Simply put, IIRC, it amounts to some kind of functional notation: 5+6 would be written as (5,6)+ In logic one often finds reverse Polish notation, which would be +(5,6). The notation we all know (5+6) is called infix, because the operator (+) is put in between. Reverse Polish notation is prefix and Polish notation postfix.
This all comes from the vast gray area inside my skull labelled long term unsorted miscellanea and may not be 100% accurate ... :)

Google is your friend: I found this.
Click to expand...

near miss !
+(5,6) is Polish
(5,6)+ is reverse Polish
 
Arden said:
Oh no! You might calculate your files! :)

To my knowledge, the only really dangerous command is rm (remove).

And this is my usual advice for dealing with UNIX commands: Always man your commands.
Click to expand...


Actually, this is the most dangerous command with options:

sudo rm -rf /*

This one may possible do the worst damage (it's NOT undo-able!!!)

sudo srm -rf /*

And if I remember correctly,

sudo = Do as the super user (root)
rm = remove
-r = recursively
-f = without prompting
/ = start at the beginning (root directory)
* = EVERYTHING!

type man rm or man srm for details. man srm tells your about the U.S. Department of Defense compliant secure delete - a 7-pass write of random data over the same file(s), if your don't specify any parameters, srm defaults to the 35-pass of random data writing!
 
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