和NASM不同，GNU Assembly(简称gas)使用的是AT&T语法。
gas使用的汇编编译器在binutils里，可执行命令为as。
以下是nasm(intel风格)和gas(att风格)的helloworld版本：

;nasm intel
section .text    ;section declaration
   ;we must export the entry point to the ELF linker or
    global _start ;loader. They conventionally recognize _start as their
   ;entry point. Use ld -e foo to override the default.
_start:
;write our string to stdout
        mov     edx,len ;third argument: message length
        mov     ecx,msg ;second argument: pointer to message to write
        mov     ebx,1   ;first argument: file handle (stdout)
        mov     eax,4   ;system call number (sys_write)
        int     0x80 ;call kernel
;and exit
 mov ebx,0 ;first syscall argument: exit code
        mov     eax,1   ;system call number (sys_exit)
        int     0x80 ;call kernel
section .data    ;section declaration
msg     db      "Hello, world!",0xa ;our dear string
len     equ     $ - msg                 ;length of our dear string

#gas,att
.text     # section declaration
   # we must export the entry point to the ELF linker or
    .global _start # loader. They conventionally recognize _start as their
   # entry point. Use ld -e foo to override the default.
_start:
# write our string to stdout
 movl $len,%edx # third argument: message length
 movl $msg,%ecx # second argument: pointer to message to write
 movl $1,%ebx  # first argument: file handle (stdout)
 movl $4,%eax  # system call number (sys_write)
 int $0x80  # call kernel
# and exit
 movl $0,%ebx  # first argument: exit code
 movl $1,%eax  # system call number (sys_exit)
 int $0x80  # call kernel
.data     # section declaration
msg:
 .ascii "Hello, world!\n" # our dear string
 len = . - msg   # length of our dear string

gas支持intel语法

由于两种语法差异比较大，同时学习两种语法比较困难，如果可以在gas里编写intel语法风格的汇编代码最好不过。实际上gas自binutils 2.11之后也支持intel语法，具体参看：http://www.mirbsd.org/htman/i386/man7/gas-intel-howto.htm 和 http://www.study-area.org/cyril/opentools/opentools/x969.html
最基础的用法是在代码首行编写：

.intel_syntax noprefix