Linux assembly language comparison: GNU Assembler (GAS) vs Netwide Assembler (NASM)

Posted on in Categories Howto, Linux, programming, UNIX last updated October 24, 2007

This article explains some of the more important syntactic and semantic differences between two of the most popular assemblers for Linux®, GNU Assembler (GAS) and Netwide Assembler (NASM), including differences in basic syntax, variables and memory access, macro handling, functions and external routines, stack handling, and techniques for easily repeating blocks of code.

Unlike other languages, assembly programming involves understanding the processor architecture of the machine that is being programmed. Assembly programs are not at all portable and are often cumbersome to maintain and understand, and can often contain a large number of lines of code. But with these limitations comes the advantage of speed and size of the runtime binary that executes on that machine. Even though the differences between these two assemblers are substantial, it’s not that difficult to convert from one form to another. You might find that the AT&T syntax seems at first difficult to understand, but once mastered, it’s as simple as the Intel syntax.

=> Linux Assemblers: A Comparison of GAS and NASM

FreeBSD Display Information About The System Hardware

Posted on in Categories FreeBSD, Hardware, Howto last updated February 23, 2005

FreeBSD comes with different utilities, which can be use to gathered the information as per your needs. uname command is use to print system information. dmesg command is use to print kernel ring buffer information. sysctl command is use to configure kernel parameters at runtime as well as to read hardware information.

Following list summaries, all the command you need to gather FreeBSD hardware information.

1) Determining the Hardware Type/platform:
# uname -m
2) Determining machine processor architecture:
# uname -p
3) Determining FreeBSD release level:
# uname -r
Generally, following command is use to get all info at a time:
# uname -mrs

FreeBSD 5.0-RELEASE i386

4) Determining CPU information such as speed, make etc
# dmesg | grep CPU

CPU: Pentium 4 (1716.41-MHz 686-class CPU)
acpi_cpu0:  on acpi0
acpi_cpu: CPU throttling enabled, 8 steps from 100% to 12.5%

5) Determining real and available memory to FreeBSD:
# dmesg | grep memory

real memory  = 201326592 (192 MB)
avail memory = 188555264 (179 MB) 

Alternatively, try following command to grab memory information:
# sysctl -a | grep hw.*mem
# sysctl -a | grep mem


hw.physmem: 194985984
hw.usermem: 167641088
hw.cbb.start_memory: 2281701376

Note systcl has more info, just type the sysctl command to see rest of all information:
# sysctl -a | less
6) Determining how long a system has been up:
# uptime
7) Determining when a system was last rebooted or shutdown:
# last -1 reboot
# last -1 shutdown

8) Determining swap file system usage
# swapinfo -k
9) Determining who is logged in and what they are doing. Following all commands can be used. users command displays the list of all logged in users only.
# w
# who
# users

10) Find out when user was last logged in – You can use last command as follows:
# last user-name
(a) To find out user vivek was last logged, enter:
# last vivek

See FreeBSD getsysinfo.bash script. It is use to find general FreeBSD system information such as, hostname, OS version, Kernel version, Processor/CPU, Total RAM, System load, network interface, total logged in users, Hard disks, Runlevel etc. Make sure your read the detailed installation instruction.