Bitwise negation Post: 302117985

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Top Forums Shell Programming and Scripting Bitwise negation Post 302117985 by dLloydm on Thursday 17th of May 2007 01:37:45 PM

05-17-2007

Registered User

This has been very helpful. It reveals to me that UNIX is storing signed integer values just like most programming languages I am familiar with. The leading 1's for negative numbers would indicate that the highest order bit is a sign bit. Therefore 2#1010 is 10 and -2#1010 is -10 which would be represented as:
111....1110110 - depending on the bit size used.

Therefore I am suspecting the course is not correct when it claims ((~ 2#1001)) evaluates to 2#110, but that it actually evaluates to:
"-2#1010".

If UNIX used unsigned integers in this case then it would evaluate to a very large number depending on the bit size used. Something like 2#111...11110110. From your analysis I do not suspect this is the case.

There is one more thing I would like to verify. The course has the following question:
What do you think is the output of the following piece of code?
((x = 2#1101 & 2#110))
((y = ~x))
print - $y

The answer given is 11, as in decimal eleven or 2#1011.
From what I understand I think the answer should be -5 as in -2#101.

I plan to inform the course provider of these possible issues but I would like to make sure there is an issue. Thanks for your help.

dLloydm

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fusioninventory::agent::tools::unix

FusionInventory::Agent::Tools::Unix(3pm)		User Contributed Perl Documentation		  FusionInventory::Agent::Tools::Unix(3pm)

NAME

       FusionInventory::Agent::Tools::Unix - Unix-specific generic functions

DESCRIPTION

       This module provides some Unix-specific generic functions.

FUNCTIONS

   getDeviceCapacity(%params)
       Returns storage capacity of given device, using fdisk.

       Availables parameters:

       logger a logger object
       device the device to use

   getIpDhcp
       Returns an hashref of information for current DHCP lease.

   getFilesystemsFromDf(%params)
       Returns a list of filesystems as a list of hashref, by parsing given df command output.

       logger a logger object
       command the exact command to use
       file the file to use, as an alternative to the command

   getFilesystemsTypesFromMount(%params)
       Returns a list of used filesystems types, by parsing given mount command output.

       logger a logger object
       command the exact command to use
       file the file to use, as an alternative to the command

   getProcessesFromPs(%params)
       Returns a list of processes as a list of hashref, by parsing given ps command output.

       logger a logger object
       command the exact command to use
       file the file to use, as an alternative to the command

   getRoutingTable
       Returns the routing table as an hashref, by parsing netstat command output.

       logger a logger object
       command the exact command to use (default: netstat -nr -f inet)
       file the file to use, as an alternative to the command

perl v5.14.2							    2012-06-25				  FusionInventory::Agent::Tools::Unix(3pm)