Retrieving command line args in gas

Question

I am struggling to find a way to retrieve first character of the first command line argument in GAS. To clarify what I mean here how I do it in NASM:

main:   
    pop ebx
    pop ebx
    pop ebx            ; get first argument string address into EBX register
    cmp byte [ebx], 45 ; compare the first char of the argument string to ASCII dash ('-', dec value 45)
    ...

EDIT: Literal conversion to AT&T syntax and compiling it in GAS won't produce expected results. EBX value will not be recognized as a character.

Answer 1

Ok I figured it out myself. Entry point should NOT be called main, but _start. Thanks Basile for a hint, +1.