Random number generator in x86 MacOS assembly (AT&T) syntax

x86macasm_rdm_number.s

# The most awesome, awe inspiring random number generator ever
# Error codes:

# 0x0 - Could not open file
# 0x1 - No bytes read from file

.bss

.data
    output: .asciz "Random number: %i \n"

    path: .asciz "/dev/random"

    fd_is: .asciz "The File descriptor is: %i \n"

    end_message: .asciz "I hope you enjoyed the most awe inspiring random number generator ever\n"
    error_message: .asciz "Error code: %i\nExiting..."

    .lcomm buffer, 4
    .lcomm fd, 4

.text

	.globl _main        

	_main:

        # First open the file?
        # int open(const char *path, int flags, ...)
        subl $0x04, %esp            # Pad the stack
        pushl $0x0                  # This is the flag for O_RDONLY
        pushl $path                 # Then add the path

        call _open                  # Make the call to open
        movl %eax, fd               # Put the file descriptor into the fd variable

        addl $0xC, %esp

        # Check for errors
        cmpl $0x0, fd
        movl $0x0, %eax
        jl error

        # Ok now we have to read from the file
        # ssize_t read(int fd, void *buf, size_t nbytes);
        pushl $0x4                  # We want to read 4 bytes
        pushl $buffer               # Provide the buffer
        pushl fd                    # And our file descriptor

        call _read                  # Read the file :)

        addl $0xC, %esp

        # Check for errors
        cmpl $0x0, %eax
        movl $0x1, %eax
        je error

        # Ok, now because we want a number between 0-15, we need to do some arithmetic :)
        movl buffer, %eax
        and $0xF, %eax              # 00001111
        movl %eax, buffer

        # Now we need to display what we read
        pushl $0x4
        pushl buffer
        pushl $output

        call _printf

        addl $0x4, %esp

        # Let's close the file
        # int close(int fd);
        pushl fd                    # Push the file descriptor onto the stack
        call _close                 # Close that bitch

        addl $0x4, %esp

        # Display a nice message and leave
        pushl $end_message          # Put our message on da stack
        call _printf                # Print the message

        # Goodbye :)
        call _exit

        nop

    error:
        subl $0x4, %esp
        pushl %eax
        pushl $error_message
        call _printf

        call _exit